Air Force Pamphlet 10-219_Vol 7 – Expedient Methods (TPD0806040)

Figure 2.23. Open Culvert Built Using Logs.    …………………………………………………………………….        32

Figure 2.24. Open French Drain Without Pipe.    ………………………………………………………………….        33

Figure 2.25. Improvised Drain Line. ……………………………………………………………………………….. .            4 3

Figure 2.26. Typical Soakaway. ……………………………………………………………………………………. …         35

2.5.      Drainage System Erosion Control and Maintenance. …………………………………………         35

Figure 2.27. Typical Check Dam With Weir Notch.    …………………………………………………………..        36

Figure 2.28. Dam Erosion Caused by Weir Notch Debris.    …………………………………………………..        37

Figure 2.29. Riprap-Lined Drainage Ditches.    …………………………………………………………………….        37

Figure 2.30. 2B22BTurnout Layout and Spacing Requirements.    ………………………………………….        38

Figure 2.31. Expedient Headwall Examples. ……………………………………………………………………..           39

Figure 2.32. Riprap and Rubble Use When There Is No Headwall.    ………………………………………        39

Chapter 3— EXPEDIENT STRUCTURAL REPAIRS                                                                       40

3.1.      Introduction. …………………………………………………………………………………………………         40

Figure 3.1.     Building Damage From Hurricane Katrina at Keesler AFB (2005).    ……………………        40

3.2.      Overview. …………………………………………………………………………………………………….         40

3.3.      Repair Considerations.  …………………………………………………………………………………..         40

3.4.      Area Clearing and Safing Practices. ………………………………………………………………..         41

Figure 3.2.     Hurricane Damage on St. Thomas, Virgin Islands (1995).     ………………………………..        43

Figure 3.3.     Examples of Asbestos Use in Construction.    …………………………………………………….        44

3.5.      Debris Clearing Operations. …………………………………………………………………………..         44

Figure 3.4.     Debris Clearing After Hurricane Andrew at Homestead AFB (1992).    ………………..        45

Figure 3.5.     Debris Clearing After Volcano Eruption in the Philippines (1991).     ……………………        46

3.6.      Structural Shoring. ………………………………………………………………………………………..         47

Figure 3.6.     Installation of Wire Rope Clips.    …………………………………………………………………….        48

Figure 3.7.     Typical Guy Wire Connection to a Structure.    ………………………………………………….        48

Figure 3.8.     Internal Guy System.    ……………………………………………………………………………………           9 4

Figure 3.9.     External Guy System.    …………………………………………………………………………………..        49

Figure 3.10. Typical Brace Configuration. …………………………….. …………………………………………        50

Figure 3.11. Externally Opposed Braces. …………………………………………………………………………..         50

Figure 3.12. Internally Opposed Braces. ……………………………………………………………………………         51

Figure 3.13. Shoring Jack Installation. ………………………………………………………………………………         51

Figure 3.14. Timber Column Use. …………………………………………………………………………………….            2 5

Figure 3.15. Support of Damaged Load Bearing Walls With Openings. ………………………………..         53

Figure 3.16. Steel Plate Splint.    …………………………………………………………………………………………        53

Figure 3.17. Use of Steel Angles at Corners of a Damaged Column.   …………………………………….         54

Figure 3.18. Use of Wound Spiral to Repair Column.    …………………………………………………………        54

Figure 3.19. Tension Ties. ……………………………………………………………………………………………….         55

Figure 3.20. Stitching Dogs. …………………………………………………………………………………………….         55

3.7.      Expedient Repair of Damaged Facilities. …………………………………………………………         55

Figure 3.21. Gusset Plate Repairs.    ……………………………………………………………………………………        57

Figure 3.22. Using Plastic to Cover a Damaged Roof. ………………………………………………………..            58

Figure 3.23. Temporary Tarpaulin Protection. ……………………………………………………………………         59

Figure 3.24. Typical Plastic Sheeting Wall Repair.    …………………………………………………………….        60

Figure 3.25. Examples of Sheathing Damage. ……………………………………………………………………           62

Figure 3.26. Damaged Brick Infill Wall.    …………………………………………………………………………..        62

Figure 3.27. Correcting Damage With New Material.    …………………………………………………………        63

Figure 3.28. Extensive Structural Wall Damage at Homestead AFB. (1992)    …………………………        64

Figure 3.29. Progressive Structural Damage in Guam (1999). ……………………………………………..           64

Figure 3.30. Masonry Wall Confining Sequence.    ……………………………………………………………….        65

Figure 3.31. Epoxy Application. …………………………………………………………………………………… …         66

Figure 3.32. Sandbagged Entrance. …………………………………………………………………………………..            7 6

Figure 3.33. Lightweight Fabric Hangar.    …………………………………………………………………………..        68

Figure 3.34. Typical Fabric Clamp Repair. ………………………………………………………………………..           69

Figure 3.35. Typical Heat/Solvent -Welded Patch Repair.    …………………………………………………..        69

Figure 3.36. Large Hole/Tear Adhesive Repair Steps.    ………………………………………………………..        71

Figure 3.37. Larger Hole Sealer Repair. ……………………………………………………………………………            72

3.8.      Conversion of Alternate Facilities. ………………………………………………………………….         72

Chapter 4— EXPEDIENT REPAIR OF WATER AND WASTE SYSTEMS                                   73

4.1.      Introduction. …………………………………………………………………………………………………         73

4.2.      Overview. …………………………………………………………………………………………………….         73

Attachment 1— GLOSSARY OF REFERENCES AND SUPPORTING INFORMATION          181

Attachment 2— CRACK REPAIR USING EPOXY INJECTION METHOD                                188

Chapter 1 INTRODUCTION

1.1.    Purpose. This volume was developed to provide deployed Airmen w ith alternative methods of accomplishing certain engineering tasks when there is insufficient time or materials or it is impractical to employ conventional methods. Information regarding installation of standard expedient construction sys- tems such as Basic Expeditionary Airfield Resources (BEAR), is beyond the scope of this publication, but is available in other pamphlets in this series.

1.2.    Overview. This pamphlet contains illustrations of basic material applications and construction meth- ods that have proven their worth during field applications. Any data and definitions presented are general in nature and should be used solely as guides. Detailed drawings are provided throughout this publication to help supervisors illustrate and explain requiremen ts to their craftsmen. The data presented herein applies primarily to a field construction force operation in a remote or bare base area ( Figure 1.1.) ham- pered by shortages of standard constr uction materials. However, it will be evident that some procedures may be relevant and helpfu l during peacetime disaster response. In addition,  many of the techniques described may apply during post-att ack recovery efforts. For the pu rpose of this doc ument, the word “expedient” is defined as: “a m eans devised or employe d in a time and place where prompt action is essential.” Expedient engineering definitely does not preclude usi ng normal engineer practices where time and materials are available.

Figure 1.1. Typical Desert Bare Base Beddown.

1.3.    Environmental Considerations. The United States Air Force is committed to achieving and main- taining environmental quality to protect US intere sts. Upholding a high level of environmental quality during training exercises or actual contingencies is a dif ficult challenge that must be achieved. T o this end, all Air Force personnel involved in these operations are charged with environmental stewardship. In no way is the intent of this res ponsibility either removed or diminis hed simply because expedient mea- sures are to be employed. Further information on how to integrate environmentally responsible practices during contingency operations can be found in Ai r Force Handbook 10-222, Volume 4, Environmental Guide for Contingency Operations.

1.4.    Task Identification. As a general rule, this volume attemp ts to address only expedient field con- struction and repair tasks that are accomplished during wartime or contingencies. However, some con- struction and repair tasks addressed in this pamphlet may also be employed during disaster recovery operations when immediate action is necessary and resources are limited.

1.5.    General Safety Practices. One of the first rules fo r response to a ny situation requiring expedient applications is to be flexible a nd remain safe. Supervisors must alwa ys keep safety in mind when using nonstandard construction methods and materials. Losing or injuring personnel or disabling equipment during field operations can severely impact miss ion accomplishment. Never compromise personnel and equipment safety when implementing the expedient procedures described in this pamphlet.

1.5.1.     Whether working alongside other military units; federal, state, an d local disaster recovery forces; government civilian employ ees and contractors; or traine d and untrained volunteers, it is essential that everyone involved is aware of the procedures used to identify hazards.

1.5.2.    To ensure safety, crew leaders should know the capabilities and limitations of assigned person- nel and monitor all work ef forts. In addition, make certain that activities are coordinated with all involved. For example, debris removal in and around facilities is a dangerous, critical task. Vibrations from heavy equipment can cause a building to collapse on recovery workers.

1.5.3.    When working in a contaminated environment, be sure to wear the appropriate individual pro- tective equipment (IPE) for the hazard present. Wash contaminated clothing and take a shower as soon as possible after working in a contaminated environment. Even when working in an environment that is not contaminated, wear protective equipment for dust, noise, sharp objects, and construction mate- rials. Plywood and lumber, brick and block, and sheet metal can all cause cuts and injuries. Even a small cut can develop into a serious injury if the wound becomes infected.

Chapter 2

ROAD AND DRAINAGE SYSTEM CONSTRUCTION AND REPAIR

2.1.    Introduction. Expedient construction and repair of road s and drainage system s during disasters or after an attack could be crucial torecovery operations and mission sustainment. These efforts may include tree clearing, grubbing and strippi ng; grading and assessing the drai nage system; repairing existing or constructing new roads and drainage systems; and implementing draina ge system erosion control prac- tices and maintenance. In remotelocations, or during post-attack operations, engineer personnel may have few supplies and resources to accomplish needed cons truction and repair. In this type of environment, engineers will need to use ingenuity , available resources, and a lot of backbreaki ng labor to accomplish the mission.

2.2.    Overview. The concepts and examples in this chapter may be applied singularly or in combination or may be modified to suit fieldconditions for expedient construction. By using these procedures, an engi- neer contingent faced with resource shortfalls may be able to meet the minimum requirements for mission accomplishment until additional resources become available. The topics presented in this chapter consist of expedient road construction and repair , expedient drainage construction and repair, and drainage sys- tem erosion control and maintenance. Note: Information regarding airfield pavement repair procedures is contained in Unified Facilities Criteria (UFC) 3-270-07, O&M: Airfield Damage Repair.

2.3.    Expedient Road Construction and Repair. Establishment of useable roadways during disa ster recovery operations or after an attack is crucial. Tasks may be as simple as clearing existing pavements or as arduous as actually constructing new surfaces. At austere sites where equipment and materials are lim- ited, expedient construction and repair measures may be needed to provide workable surfaces in a timely fashion. The expedient road construc tion methods discussed in this chap ter are: wire mesh; sand grid; plank tread; landing mat; and snow and ice. In addition, soil cement, geo-fiber, lime, and fly ash stabiliza- tion procedures are also discu ssed. Field Manual (FM) 5-34, Engineer Field Data and FM 5-430-00-1, Planning and Design of Roads, Airfields, and Heliports in the Theater of Operations—Road Design, pro- vide further options for dealing with problems related to expedient road construction.

2.3.1.    Expedient Road Construction Methods.

2.3.1.1.    Wire Mesh. Chicken wire or chain-link (cyclone) fencing material may be used for expe- dient surfaces over sand. Adding a layer of burla p or similar material und erneath the wire mesh helps confine the sand. Longer life can be obtained by proper subgrade preparation, multilayer or sandwich construction, and staking the edges of the wire mesh at 3-foot intervals. As indicated in Figure 2.1., diagonal wires that cross the centerline at 45-degree angles and are securely attached to buried pickets fortify the lighter meshes. The more layers used the more durable the surface will become. Other roads should never cross wire-mesh roads unless planking or some such material is placed over the mesh to protect it. In addition, mesh surfaces should not be used on muddy roads because they prevent grading and reshaping of the surface when ruts appear. Commercial wire/ fabric barriers, laid flat, prov ide similar confinement and separation as the wire mesh/burlap and may be more available in the area of responsibility (AOR).

Figure 2.1. Wire-Mesh Road Construction Details.

2.3.1.2.    Sand-Grid Roads. This technique involves the conf inement of sand or sandy materials in interconnected cellular elements called grid s (Geocells) to produce a load-distributing pave- ment base layer. It has application in areas where sandy materials are abundant and quality con- struction aggregates are not av ailable. A sand-grid road over a sand subgrade is capable of supporting over 10,000 passes of heavy truck traffic, including tandem axle loads of up to 53,000 pounds. The plastic honeycomb grid is manufactured and shipped in unexpanded sections that are easily expanded for field use (see Figure 2.2.). Each 4-inch-thick section expands to form a hon- eycomb arrangement of 561 cells that cover an area 8 by 20 feet and weigh 1 10 pounds. Other applications of sand-grid technology include field fortifications, slope protection, channel protec- tion, and retaining walls.

2.3.1.2.1.    When installing this material, use pickets or place sand on the corners and sides to maintain placement. After positioning the entire first layer, use a bucket loader to begin filling the grid, working from one edge of the repair to ward the center. A full grid section will hold the weight of a bucket loader. A four-person crew can quickly construct a sand-grid road using bucket loaders, light bulldozer s and vibratory compaction roll ers. The use of rough-terrain forklifts; water distributors; asphalt distribut ors; long-handled, round-point shovels; and 8-foot by 4-foot by 3/8-inch sheets of plyw ood can increase the effectiveness and speed of construction.

Figure 2.2. Typical Sand-Grid Material in Shipping Configuration.

2.3.1.2.2.    As the grids are filled, the loader can drive forward onto the grids to expand their range. Use shovels and rakes to spread the material to overfill the cells by a uniform layer of 1 to 2 inches. Provide suf ficient compaction by using a rubber-tire or steel-wheel roller. How- ever, be aware that over compaction can damage the sand grid and result in premature failure. After compacting the first layer, repeat the process, starting by placing a porous layer of mem- brane (typically permeable geotextiles or geof abrics that are lightwe ight, waterproof, and breathable). Put the top layer of sand grid with its long dimension stretched 90 degrees to the first. This makes it perpendicular to the r oad centerline and increases strength. Once again, overfill the grid cells by 1 to 2 inches. The surface can be further stabilized by applying a sand-asphalt surface of about one-gallon of RC-250 asphalt cutback per square yard. Figure

2.3. is an example of using sand grids to construct roads over rough terrain.

Figure 2.3. Sand-Grid Road Construction.

2.3.1.2.3.    When making road repairs with this material, place the initial 4-inch layer of sand grid in the crater parallel to the centerline of the roadway. Expand the sand grid, using shovels to fill the grid-edge sections to hold it in place. Cover the entire bottom of the cavity with grid material in this manner so it conforms to the shape of the repair, curving or cutting as necessary (see Figure 2.4.). Sections that do not fully expand add strength to the base. After posi- tioning the first layer , fill the grid, working fr om one edge of the repair toward the center . Compact the cells level with the pavement, using a rubbe r-tire or steel-wheel roller or vibra- tory-plate tampers, and remove any excess material after compaction. If more than one layer is needed, follow the previous instructions for sand-grid road construction.

Figure 2.4. Sand-Grid Construction Details.

2.3.1.3.    Plank-Tread Roads. Use plank-tread roads for crossing short sections of loos e sand or wet, soft ground. This type of road may last severa l months if it is well-built and has an adequate base (see Figure 2.5.).

2.3.1.3.1.    To construct a plank-tread road, first place sleepers 12 to 16 feet long perpendicular to the centerline on 3- to 4-foot centers, depending on the loadsto be carried and subgrade con- ditions. If finished ti mber is not available, logs may be used as sl eepers. Next, place 4- by 10-inch planks parallel to the li ne of traffic to form two treads about 36 inches apart. Stagger the joints to prevent forming weak spots. If desired, 6-inch curbs may be installed on the inside of the treads. When built with an adequate ba se, plank roads can last for several months. Planks 3 to 4 inches thick, 8 to 12 inches wide, and at least 13 feet long are ideal for flooring, stringers, and sleepers. When desired, 3- by 10-inch planks (rough, not finished) can replace the 4- by 10-inch timbers shown in Figure 2.5. Rough 3- by 8-inch a nd 3- by 10-inch planks can normally be cut to order.

2.3.1.3.2.    Position stringers in regular rows parallel to the centerline on 3-foot centers with staggered joints. Lay floor planks across the stringers with about 1-inch gaps when seasoned lumber is used. The gaps allo w for swelling when the lumber absorbs moisture. Spike the planks to every stringer. Place 6-inch-deep gu ardrails on each side with a 12-inch gap left between successive lengths of guardrails for surface-water drainage. Install pickets along each side at 15-foot intervals to hold the roadway in line.

Figure 2.5. Plank-Tread Road Layout Plan.

2.3.1.3.3.    To achieve proper drainage, construct the base for a plank road with a transverse slope, as shown in Figure 2.6., instead of a center crown. T o provide a smoother riding sur- face, put treads parallel to the line of traffic over floor planks.

Figure 2.6. Plank Road Construction Details.

2.3.1.4.    Airfield Landing Mats. The demand for rapidly constructed airfields led to the develop- ment of several portable, metal landing mats. As metal airfield landing mats became a standard supply item, they were quickly put to use on beaches as well as airf ields. They are still in use as expedients for crossing sandy terr ain. Landing mat designs fabricated from aluminum alloys can support heavier loads than many other materials and have a lower weight per square foot as com- pared to timbers. They also provide smoother su rfaces so that the smallest-wheeled vehicle using the road can obtain traction. The three most common types of matting employed in expedient road construction are pierced steel planking (PSP), M8A1, and AM-2 (see Figure 2.7.).

Figure 2.7. Common Landing Mat Variations.

2.3.1.4.1.    When used on sand, place the metal landing mats directly on the sand to the length and width desired. Install the mat so that its long axis is perpendicular to the flow of traffic. If a width greater than the ef fective length of one plank is required, use half sections to stagger the joints. A second layer of the steel mat, laid as a treadway over the initial layer, increases its effectiveness. If PSP is used, place an impervious membrane under the mat to smooth and firm the subgrade, thus improving the road stability.

2.3.1.4.2.     After extended use, landing mats te nd to curl at the edge s. This problem can be overcome by anchoring the edges properly. Screw-type earth anchors provide the best means of anchoring. Another method of securing the edges is to us e a curb of timber on the outside edge of the road and either wire it tightly to buried logs laid para llel to the road or stake it a s shown in Figure 2.8. In addition, the road surface must be void of high spots and ruts for mat- ting to be effective. Such irregularities cause difficulties in assembling the matting pieces.

2.3.1.5.    Snow and Ice Roads. In regions with heavy snowfall and where temperatures are below freezing for extended periods, expedient roads can be constructed over the snow. When a road is laid out over snow or ice, makegrades and curves as gentle as possible and compact the snow until it is capable of supporting the weight of the vehicles expected to use it. Once proper compaction is achieved, add water to the comp acted plane and allow it to fr eeze to produce a sounder wearing surface. Vehicle tire traction can be improved by spreading sand over the surface.

Figure 2.8. Landing Mat Anchoring Technique.

2.3.2.    Soil Stabilization Techniques. In addition to expedient r oad construction procedures addressed previously, mechanical and chemical soil stabilization tech niques can be used to bolster road surfaces during contingencies ( Figure 2.9.). Many of these approaches can be ef fective for extended periods. Mechanically stabilized soil mixtures are widely used as surfaces for military roads to carry light traffic where difficult soil conditions exist. Chemical admixtures are often used to stabi- lize soils when mechanical methods are inadequate and replacing an undesirable soil with a desirable soil is not an option. Most chemical admixture stabilization projects involve the use of cement, lime, or fly ash. While both of these methods appear to be labor intensive, they are quite the opposite when compared to standard road cons truction methods. In terms of mate rial, both processes are less costly than normal road construction involving asphalt or concrete. Warning. The use of cement, lime or fly ash to stabilize a soil with a high content of sulfates (as present in many Southwest Asia (SWA) coun- tries) can lead to heave from ettri ngite formation. Engineers may need to have soil tested for sulfate content before selecting a stabilization agent.

Figure 2.9. Stabilizing a Tent Area in French Guinea.

2.3.2.1.    Chemical Mixtures Methods. Although effective, there ar e hazards associated with chemical stabilizers. When working with these materials, refer to detailed information listed in the Material Safety Data Sheet (M SDS) prepared by the manufactur er. Generally, the hazard of air- borne particles is reduced signifi cantly in the open air on the c onstruction site. General informa- tion is also provided in FM 5-410, Military Soils Engineering, Appendix C.

2.3.2.1.1.1.     Soil-Cement’s Advantages. Soil-cement’s advantages include high strength and durability combined with low first cost, making it an economical material. About 90 percent of the material needed for soil-cement is already i n place, keeping handling and hauling costs to a minimum. Like concrete, so il-cement continues to gain strength with age. Because soil-cement is compacted into a tight matrix during construction, the pave- ment does not deform under traf fic or develop potholes l ike unbound aggregate bases. Soil-cement is capable of br idging over weak subgrade areas and is highly resistant to deterioration caused by seasonal moisture changes and freeze/thaw cycles.

2.3.2.1.1.2.     Installation Steps. Tests must be performed to determine the proper cement content, compaction, and water requirements for the soil material used. Soil-cement can be mixed in either a central plant or mixed in place. However , during contingency situations involving expediency, mixing the material in place is often the obvious choice. For in-place operations, either clay or granular soils ca n be used. During a mixing-in-place operation, always follow the four basic soil-cement paving steps: spreading, mixing, com- pacting, and curing.

2.3.2.1.1.2.1.     When the roadway has been shaped to grade and the soil loosened to a depth of 8 to 10 inches, the proper quantity of cement is spread on the in-place soil.

2.3.2.1.1.2.2.       The cement is then thoroughly mixed into the soil and the required amount of water is added.

2.3.2.1.1.2.3.     The mixture is then tightly compacted with rollers, shaped to the proper contour and rolled again to achieve a smooth finish. Finally, to supply and maintain the moisture needed for hydration, the soil-cement is sprayed with water and sealed with a bituminous mixture. Further information regarding soil-cement procedures can be found in HQ AFCESA Enginee ring Technical Letter (ETL) 01-06, Contingency Air- field Pavement Specifications. This document can be downloaded from the AFCESA web site:

https://www.my.af.mil/gcss-af/USAF/AFP40/Attachment/20070629/ ETL%2001-6.pdf

2.3.2.1.2.    Lime. Experience has shown that lime reacts with medium, moderately fine, and fine-grained soils to produce de creased plasticity, increased workability and strength, and reduced swell. Several soil classifications in the U nified Soils Classification System (USCS) are potentially capable of being stabilized wi th lime. Additional data on lime stabilization actions can be found in FM 5-410.

2.3.2.1.2.2.     Lime can be used either to modify some of the physical properties and thereby improve the quality of a soil or to transform the soil into a stabilized mass, which increases its strength and durability. The amount of lime additive depe nds on whether the soil is to be modified or stabilized. Th e lime to be used may be either hydr ated or quicklime, although most stabilization is done using hydrat ed lime. The reason is that quicklime is highly caustic and dangerous to use.

2.3.2.1.2.3.     When lime is added to a soil, a comb ination of reactions begins to take place immediately. These reactions are nearly complete withi n one hour, although substantial strength gain is not reflected fo r some time. The reactions result in a change in both the chemical composition and the physical properties. Most lime has a pH of about 12.4 when placed in a water solution. Therefore, the pH is a good indicator of the desirable lime con- tent of a soil-lime mixture. The reaction that takes place when lime is introduced to a soil generally causes a significant change in the plasticity of the soil.

2.3.2.1.3.    Fly Ash. Fly ash consists mainly of silic on and aluminum compounds that, when mixed with lime and water , forms a hardened cementitious mass capable of obtaining high compression strengths. Fly ash is a by-product of coal-fired, el ectric-power-generation facili- ties. The liming quality of fly ash is highly dependent on the type of coal used in power gener- ation. Fly ash is categor ized into two broad classes by its calcium oxide (CaO) content. They are: Class C and Class F. Refer to FM 5-410 for more information on fly ash stabilization.

2.3.2.1.3.1.     Class C. This class of fly ash has a high CaO content (12 percent or more) and originates from sub-bituminous and lignite (soft) coal. Fly ash from lignite has the highest CaO content, often exceeding 30 pe rcent. This type can be used as a stand-alone stabiliz- ing agent. The strength characteristics of Class C fly ash having a CaO less than 25 percent can be improved by adding lime.

2.3.2.1.3.2.     Class F. This class of fly ash has a low CaOcontent (less than 10 percent) and originates from anthracite and bituminous coal. Class F fly ash has an insuf ficient CaO content for the po zzolanic reaction to occur. It is not effective as a stabilizing agent by itself; but when mixed with lime or lime and cement, the fly ash mixture becomes an effec- tive stabilizing agent.

2.3.2.1.3.3.     Lime Fly Ash (LFA) Mixtures. LFA mixtures can contai n either Class C or Class F fly ash. The LF A design process is a four-part process that requires laboratory analysis to determine the op timum fines (particles passing a Number 200 sieve) content and lime-to-fly-ash ratio. The op timum fines content is the percentage of fly ash that results in the maximum density of the soil mix. The initial fly ash content should be about 10 percent based on the weight of the total mi x. The design fines content should be 2 per- cent above the optimum fines content. For example, if 14 per cent fly ash yields the maxi- mum density, the design fines content would be 16 percent. The moisture density relation would be based on the 16 percent mixture. LFA is constructed in laye rs not less than 4 compacted inches. Final thickness and actual proportions are set by the engineer. After LFA has been constructed, the surface must be kept moist until a bituminous curing cover is applied.

2.3.2.1.3.4.     Lime-Cement-Fly Ash (LCF) Mixtures: The design methodology for deter- mining the LCF ratio for delibe rate construction is the same as for LFA except cement is added at the ratio of 1 to 2 percent of the design fines content. Ceme nt may be used in place of or in addition to lime; however , the design fines content should be maintained. When expedient construction is required, use an initial mix proportion of 1 percent Port- land cement, 4 percent lime, 16 percent fly ash, and 79 percent soil. Minimum unconfined strength requirements (see Table 2.1.) must be met. If test specimens do not meet strength requirements, add cement in 1/2 percent increments un til strength is adequate. Note: As with cement-stabilized base course material s, LCF mixtures containing more than 4 per- cent cement cannot be used as base course material under Air Force airfield pavements.

Table 2.1. Minimum Strengths for Stabilized Soils.

2.3.2.2.    Mechanical Mixture (Sand Fiber) Method. The Army Engineer Research and Devel- opment Center (ERDC) in Vicksburg, Mississippi, developed this rapid-road-construction method to overcome sandy and soft soil deficiencies. Theroad construction procedure involves stabilizing sand with geofibers, also known as sand fibers. The effectiveness of this approach has been veri- fied through extensive testing at the ERDC testing facilities.

2.3.2.2.1.    Sand-fiber ro ad stabilization technology involv es mixing small amounts (0.8 per- cent by weight) of hair-like, 5-centimeter-long (2 inches) polypropylene fibers into moist sand with a rotary mixer ( Figure 2.10.). The sand-fiber layer is then compacted with a smooth-drum vibratory roller. Next, a wearing s urface is added by spraying a re sin-modified emulsion or emulsified asphalt onto the road surface to bond the sand grains with the fiber fil- aments and protect the sand-fiber surface.

2.3.2.2.2.    Using the geofiber cons truction method, military supply roads can be constructed quickly at remote sites, over beaches, or acros s desert sands with less equipment, manpower, and materials than ot her road-building methods require. Experiments conducted at ERDC indicate that roads constructed with this new technologycan carry over 10,000 passes of heavy military supply traffic with very little or no maintenance required. Sand-fiber stabilization uses existing military construction equipment and re quires no special construc tion skills. In addi- tion, it can be used on a wide variety of sands and silty soils found around the world. Table

2.2. lists soil stabilization me thods for specific applicati ons. For additional information regarding geofiber soil reinforcement, obtain US Army Engineer Waterways Experiment Sta- tion (1999) Technical Report GL-99-03, Discrete Fiber Reinforcement of Sands for Expedient Road Construction, at http://libweb.wes.army.mil.

Figure 2.10. Blending Fibers With Soil.

Table 2.2. Stabilization Methods Most Suitable for Specific Applications.

2.3.2.3.    GeotextilesTechnique. Another technique available for improving the condition of soils besides mechanical blending and chemical stab ilization involves the us e of geotextiles (see Fig- ure 2.11.). The term geotextile refers to any permeable textil e used with foundation, soil, rock, earth, or any other geotechnical engineering-related material as an integral part of a human-made project, structure, or system. Geotextiles are also commonly referred to as geofabrics, engineering fabrics, or just fabrics.

Figure 2.11. Using Geotextile During Road Construction.

2.3.2.3.1.    Geotextiles serve four primary functions: reinforcemen t, separation, drainage, and filtration. In many situations, using these fabrics can replace soil, which saves time, materials, and equipment costs. In theater -of-operations horizontal construction, the primary concern is with separating and reinforcing low load-bearing soils to reduce construction time.

2.3.2.3.2.    The design engineer attempts to reduce the thickness of a pavement structure when- ever possible. Tests show that for low load-bearing soils (generally anything less than a 5 CBR value) the use of geofabrics can often decrease the amount of subbase and base course materi- als required. The fabric lends its tensile stre ngth to the soil to incre ase the overall design strength. Figure 2.12. shows an example of this concept.

2.3.2.3.3.    Swamps, peat bogs, and beach sa nds can also be quickly stabilized by the use of geofabrics. The normal solution is to remove the poor base material by a process commonly referred to as “mucking.” However, this is not an option during most contingencies for a num- ber of reasons. Specifically, the removal pro cess is often very dif ficult and time-consuming. Furthermore, it can only be used if the area has sound, stable so il underneath the soft soil and a suitable fill ma terial is available near by. Consequently, during contingencies, a bridge of base course construction material is usually placed directly over the weak soil separated by a layer of geotextile material, as shown in Figure 2.13. The basic construction sequence for the direct fill process is shown in Figure 2.14. Specific geotextile application details are provided in FM 5-410 and UFC 3-220-08FA, Engineering Use of Geotextiles.

Figure 2.12. Comparison of Aggregate Depth Requirements.

Figure 2.13. Using Geofabric to Separate Construction Materials.

Figure 2.14. Basic Geotextile Construction Sequence.

2.3.2.3.4.    Choosing Geotextiles. A wide range of geotextile fabr ic is available to meet vari- ous soil conditions. Selection of the proper geot extile will depend o n the actual soil and hydraulic conditions. The general soil conditions and considerations listed in Table 2.3.should provide some in sight into selecting th e optimum material. Fu rther information about geotextile uses is available in FM 5-410 and UFC 3-220-08FA.

2.3.2.4.    Other Surface Options. A number of other materials can be used to construct expedient road surfaces. A few examples incl ude rubble, bricks, concrete blocks, timbers, and loose aggre- gate or gravel. Detailed information on expedient road construction variations can be found in FM 5-430-00-1.

Table 2.3. Soil and Hydraulic Conditions.

2.4.    Expedient Drainage Construction and Repair. Removing surface water and water runoff away from roads, buildings, and other structures is critical during disasters or after an attack. The use of cul- verts, ditches, and other drainage methods may be necessary to prev ent erosion of key building founda- tions and roadways or to clear floodwaters from housing and industrial areas.

2.4.1.    Expedient Culvert Designs: Expedient culverts can be cons tructed from a wide varie ty of materials. A few of the more common variations include sand bags, pierced steel planks, and empty oil, gasoline, or asphalt drums. Culverts constructed of timber or logs are usable in the field as tempo- rary measures until structures that are more permanent can be employed. In both of these instances, an area equal to the end area of anappropriately sized corrugated metal pipe (CMP) or concrete pipe out- let, on the same slope, can be used for hydraulic capacity.

2.4.1.1.    Oil Drum Culverts (Figure 2.15.). When empty drums are used, the capacity of the cul- verts can be assumed to be equivalent to the same diameter CMP set at a comparable slope. Note: If using drums as culverts, take extreme care when using a cutting torch to remove the lids. Joints between drums should be welded solid. However , if this cannot be accomplished, tack welds can be used if provisions are made to seal the join ts to prevent the culvert water from saturating the surrounding fill material.

Figure 2.15. Expedient Oil Drum Culvert.

2.4.1.2.    Log or Timber Box Culverts. When constructing a log or a timb er culvert, the cover should be greater than the top width of the box (seeFigure 2.16.). Joints should be as tight as prac- ticable and, if plausible, covere d with some type of sealing ma terial (such as plastic sheeting, asphalt, or tar) to prevent water seepage. If such material is not available, caulk with leaves and brush. If logs are to be used, in order to obtain maximum structural strength, logs should be trimmed where required to ensure proper seating and securely fastened with spikes or driftpins (see Figure 2.17.). In order to reduce j oint openings, always lay logs butt to tip. To prevent the movement of soil through log openings, double-layer the top logs with burlap or brush. This step also applies to culverts made of sandbags and pi erced steel planks if a paved surface is not used (see Figure 2.18. and Figure 2.19.). Note: A minimum cover of three feet over a culvert of this type is required.

2.4.2.    Open-Ditch Design. From an expedient construction perspe ctive, the shape of a ditch is usu- ally governed by the engineer equi pment available. The road grader will probably be the most com- mon heavy equipment item used. T riangular ditches are appropriate for most situations; they can be symmetrical or nonsymmetrical. If large quantities of runoff are probable, a trapezoidal ditch can be excavated. Do not be conservative when it comes to sizing drainage ditches; an oversized ditch will cause much less problems than one that is too small.

Figure 2.16. Expedient Log Box Culvert.

Figure 2.17. Spiking and Fastening a Log Box Culvert.

Figure 2.18. Expedient Sandbag Culvert.

Figure 2.19. Expedient Metal Plank Culvert.

2.4.3.    Deflectors. To remove water off the surface of an expedient road, a deflector can be installed. Deflectors are particularly ef fective on sloping roads and help to stop channeling and rutting of the road surface. A deflector is simply a piece of rubber belting 3/8- to a 1/2-inch thick fastened between treated timbers. An unserviceable ar resting barrier tape could also be used if a flat rubber belt is not available. The timbers are buried at a slight angle across the roadway with only about 3 inches of the belt exposed (see Figure 2.20. and Figure 2.21.). As water runs down the surface of the roadway, it is intercepted by the belt and is dispersed off to the side. It is common practice to place riprap at the dis- persal end of the deflector to prevent erosion of the shoulder and side slopes of the road.

Figure 2.20. Typical Deflector Installations.

Figure 2.21. Deflector Construction Details.

2.4.4.    Open Top Culverts. The open top culvert ( Figure 2.22.) is another way to remove surface water away from the surface of roads. This met hod consists of a “U” shaped wooden trough made of treated lumber. This trough is installed flush with the roadway surface and angled 30 to 45 degrees downgrade. The outlet end of this type of culvert should extend beyond the edge of the road, and riprap should be placed atthe outlet end to prevent erosion. Thistype of culvert generally requires reg- ular maintenance; consequently, it should only be used on roadways with minimum grades. If treated lumber is not readily available, an open culvert can also be fabricated using natural material as shown in Figure 2.23. where logs were employed.

Figure 2.22. Typical Open Top Culvert Example.

Figure 2.23. Open Culvert Built Using Logs.

2.4.5.    French Drains. The purpose of a French drainage syst em is to carry unwanted freestanding water away from a building. French drains, also known as blind drains, ar e commonly installed near the perimeter of a structure at the lowest point where standing water is found. The system may termi- nate at any point where the water will not drain back toward the building. Installing a French drain is usually a simple, but labor -intensive, project. However, obstacles such as tree roots, boulders , and underground utilities, can make the project difficult and time-consuming.

2.4.5.2.     In general, French drains are constructe d by filling a ditch or trench with broken or crushed rock (see Figure 2.24.). The top surface of the rock maybe left exposed so the trench will act as a combination drain or the rock may be c overed by a relatively impe rvious soil so that no surface water can penetrate. The latter is the general practice. Normally, French drains are not rec- ommended for permanent construction because they have a tendency to silt up with prolonged use. In field construction, such drains are often used as a substitute for perfo rated or open joint pipes because of logistical limitations on piping or on filter materials suitable for use with such piping. However, it is advisable to use a French drain with a perforated land drain in the bottom, which may also be wrapped in a layer of this geotextile fabric to ensure longer life by stopping any fines from clogging the system. In areas with severe drainage problems, multiple perforated pipes can be run together to act as water collectors or interceptor drains. This wa y, water is carried away more quickly when the surrounding earth is saturated.

Figure 2.24. Open French Drain Without Pipe.

2.4.5.3.    French Drain Construction Details. The basic procedure for installing a French drain that includes perforated pipe is as follows. However, keep in mind, a system can also be installed without piping and geotextile fabr ic, but its longevity may be greatly reduced due to silt transfer. From the beginning point of th e drain, dig a trench about 12 inches deep and approximately 8 inches wide. If the ground slopes upward, dig deep er from the starting po int to maintain a down- ward slope. Line the cavity with a geotextile, leav ing sufficient excess to allow it to overlap the subsequent piping and fill material . Next, pour in about 2 inches of rock (pea gravel or crushed stone). Lay a 4- to 6-inch perforated pipe over the rock with the perforations facing down. If per- forated pipe is not available, fabricate a substitute from lumber as shown in Figure 2.25. Once the piping has been installed, place another 2 inches of rock in th e opening to completely cover the pipe and fold the remaining geotextile over the stone in order to encapsulate the drain field. Lastly, back fill with soil (about 2 inches) and plant grass. Note: Water entering the tre nch will have to run to a suitable drain-of f point, and in most cases, this is a soakaway or watercourse. However , rainwater should never be discha rged into a cesspool or septic tank, and foul drai nage should never be discharged into a French drain or soakaway.

Figure 2.25. Improvised Drain Line.

2.4.6.    Soakaway: A soakaway is simply a hole in the ground filled with rubble and coarse stone with a drainage pipe laid into it to aid in removing surface (rain) water from other areas. The soil in which the soakaway i s placed must be granular with good dr ainage properties. A soakaway should not be used in clay soils. Most local au thority regulations dictate soakaways be located at least 15 feet from any habitable building. The pipe flowing to them should be at least 3 inches in diameter , however, a 4-inch pipe diameter is the recommended size. This pipe should be laid to a fall of 1 in 40. The size of the soakaway should be a minimum of 3’ x 3’ x 3’ below the bottom of the incoming pipe. The stone fill should surround the pipe and finish approximately 4 inches above it. As indicated in Figure 2.26., an impervious layer should then be placed on the stone. Materials such as thick polyethylene, tarpau- lin, or even a bed of conc rete (A1) are recommended. Topsoil can then be pl aced on top of this layer to restore the garden level (A).

Figure 2.26. Typical Soakaway.

2.4.7.    Vertical Wells. Vertical wells are sometimes constructed to permit trapped subsurface water to pass through an impervious soil or rock layer to alower, freely draining layer of soil. Additional wells are driven if drainage is obstructed or the pocket is drained with an easily maintained lateral sub-drain system. Vertical wells are often used in northern latitudes to permit fast runoff from melting snow to get through the frozen soil and reach a pervious stratum. Under such conditions, the bottoms of these wells are treated with calcium chloride or a layer of hay to prevent freezing.

2.5.    Drainage System Erosion Control and Maintenance. Erosion presents many difficult problems in designing and maintaining open channels. Erosion tends to change the shape of channels, which can cause troubles near structures such as roads, bridges, and culverts. Additionally, erosion presents problems when the displaced material is deposited in undesi red locations. The primary cause for erosion is the velocity of the water in the channel. The principle method for preventing erosion is to lower the velocity in the channel below the soil erosion velocity.

2.5.1.    Controlling Velocity. Velocity is dependent on the slope of the chann el. If the slope is increased, the velocity increases. One method of decreasing the velocity of the water in a channel is to decrease the slope. Channel velocity is also affected by the shape and depth of the channel. Making the ditch wider and shallower increases the surface area. The larger surface area causes greater friction and lowers the channel velocity. Since constructing a new ditch at a different slope is impractical, an effective alternative is to construct a check dam. Check dams are the most common structure used to reduce velocity in ditches that have longitudina l grades not exceeding 8 percent. They work by decreasing the slope of the water surface. Eventually soil is depo sited on the ditch bottom and the ditch slope itself is decreased. Check dams should be considered when the slope ranges between 2 and 8 percent. Channels with slopes of 2 percent or less generally do not require extensive erosion con- trols. Usually with slopes in excess of 8 percent, it is more economical to pave the ditch with asphalt.

2.5.2.    Constructing Check Dams. Check dams may be constructed of timber, sandbags, concrete, rock, or similar materials. They should extend at least 24 inches into the bottom and sides of the ditch, and the ditch top should be at least 12 inches above the top of the dam. The effective height of the check dam should be at least 12 inches, but not mo re than 36 inches. An ap ron of rubble or riprap should extend at least 4 feet from the face of the chec k dam on the discharge side to prevent erosion.

Figure 2.27. Typical Check Dam With Weir Notch.

2.5.3.    Check Dam Maintenance: Erosion around the dam is the most common problem associated with check dams. The primary cause for this situation is that the weir notch is too small or is clogged with debris causing water flow overthe top of the dam. This situation results in erosion where the dam is anchored into the ground (see Figure 2.28.), and if left uncorrected over time, will often result in more damage to adjacent structures than if the dam was never installed.

2.5.4.    Using Riprap and Rubble. By increasing the effective roughness of a ditch, ditch soil erosion is decreased. One easy way of doing this is with riprap and rubble ( Figure 2.29.). This method involves placing rocks or rubble in the ditch bottom to provide a pr otective cover over the soil. Nor- mally, rocks should be lar ger than 6 inches to assure stabilization. Furthermore, they should be hand-placed and compacted individually in at least two layers. The riprap not o nly prevents erosion, but will also tend to decrease the velocity in the channel. This makes it useful for lowering velocities in sections of channel when ma king transitions to so il ditches from paved or other high-velocity ditches.

Figure 2.28. Dam Erosion Caused by Weir Notch Debris.

Figure 2.29. Riprap-Lined Drainage Ditches.

2.5.5.    Using Turnouts on Roadside Ditches. If hilly terrain is encountered during the construction of expedient roads, erosion in the supporting drainage ditches may be a problem. As addressed previ- ously, one method of fighting such erosion involves us ing riprap, but the us e of turnouts might be more effective. Turnouts are channels cut from the roadside ditches to adjacent areas that can handle larger runoff quantities. Attempt to have collected water spread over an open land area. Refrain from diverting the water directly into nearby streams or lakes. Figure 2.30.shows a typical turnout arrange- ment and a chart that indicates the spacing of turnouts in respect to the grading of the road.

Figure 2.30. 2B22BTurnout Layout and Spacing Requirements.

2.5.6.    Constructing Headwalls and Wingwalls. Headwalls and wingwalls are constructed to pre- vent and control erosion, guide water into a culvert, reduce seep age, and hold the end of a culvert in place. Figure 2.31. illustrates three types of expedient headwalls. Headwalls, also known as retaining walls, are a lways employed at the upstream end of a culvert. Nevertheless, they can also be used downstream where steep grades are involved to support and protect the soil mass at the end of the cul- vert and to hold the culvert sections in place. They should be constructed of materials as durable as the culvert. Sandbags or rubble can be used in emergency situations.

2.5.6.1.    Headwalls. The inlet end of the pipe should be extended so that a minimum-sized head- wall is required. Headwalls should not protrude above the shoulder grade and should be located at least two feet outside the shoulder to avoid becoming traffic hazards.

2.5.6.2.    Wingwalls. Wingwalls are required to channeliz e water and prevent washing out of headwalls. They are set at an angle to the headwall to further support the surrounding fill and help direct the water flow. Their height should prevent embankment mate rial from spilling into the waterway. The log headwall, shown as (3) in Figure 2.31., includes wings.

Figure 2.31. Expedient Headwall Examples.

2.5.6.3.    Alternatives. Headwalls and wingwalls ar e costly to build in both time and materials. When possible, avoid this ef fort by extending the outlet a minim um distance of two feet beyond the toe of the fill. In addition, the area directly beneath the pr ojecting culvert should be well pro- tected by erosion-resistant material such as sandbags or rock riprap. Riprap should consist of rock not less than 6-inches in diamet er. Riprap should be tw o layers deep on the sides of the channel. Riprap under the culvert outfall should be at least three layers deep (see Figure 2.32.).

Figure 2.32. Riprap and Rubble Use When There Is No Headwall.

Chapter 3

EXPEDIENT STRUCTURAL REPAIRS

3.1.    Introduction. Expedient structural repair techniques are employed by Air Force engineers to protect fixed assets following a disa ster, wartime or terrorist attack, or during humanit arian assistance activities. After a wartime or terrorist attack, emergency building repair is generally limited in scope and emergency repairs are considered adequate when they allow mission-critical functions to continue. During peace- time, an emergency building repair may be required as a result of a major disaster or emergency. The type and extent of the disaster or emergency will, to a la rge degree, dictate both th e type and extent of the recovery response. Tornadoes and hurricanes are two of the more common natural disasters that af fect military installations. In the past, Altus, Homestead, and Tinker Air Force Bases suf fered heavy damage that was similar to that of an ai rfield attack from these weather phenomena. Installations and local com- munities can also experien ce fires, floods, and the af fects of volcanoes. The devastation from Hurricane Katrina at Keesler Air Force Base in 2005 (Figure 3.1.) reinforces the necessity for engineers to have the skill-sets required to expediently repair the damage generated by such storms.

Figure 3.1. Building Damage From Hurricane Katrina at Keesler AFB (2005).

3.2.    Overview. This chapter concentrates on common technique s used to make expedient or emer gency repairs to damaged structures—either civilian or military. Emergency repairs of critical facilities normally involve debris removal; demolition and/or shoring and expedient structural patching of roofing, structural openings, and exterior sheathing. The topics presented in this chapter consist of repair considerations, area clearing and safing practices, debris clearing opera tions, structural shoring, and facility expedient damage repair.

3.3.    Repair Considerations. Expedient repair of facilities must be viewed from a common sense per- spective. The following considerations should form the basis for facility repair activities.

3.3.2.    Expediency. All engineer efforts immediately following an emer gency should be limited to minimum-essential repair of crucial facilities. W ork performed should c oncentrate on functional rather than cosmetic repair. All structural repair efforts should be geared toward making a facility safe for occupancy and providing minimal protection from the elements.

3.3.3.    Mission. The importance of the facility to the overall base mission determines the repair prior- ity. Damaged facilities housing activities that are not essential to the base mission and do not present a hazard should be left as they are until time and resources permit conventional repairs.

3.3.4.    Practicality. Considerations of other re lated repair activities af fecting the facility should be taken into account. For example, if the facility pr ovides service to aircraft and all access pavements are so severely damaged that they cannot be made usable for days, the structural repair can wait. Sim- ilarly, if the supporting utility systems to a facility are far beyond emergency repair, the structural por- tion of the repair effort can be delayed. On the other hand, lack of full utility service does not mean a building will be totally useless. Afacility with partial utility service, electricity but no water for exam- ple, can still be used for its wartime purpose. The da mage control center will have to make the deci- sion as to the practicality of repair.

3.3.5.    Flexibility. Flexibility is essential to any expedientrepair effort—including ones of a structural nature. During war, expect repair priorities to ch ange; engineer efforts must adjust accordin gly. As might be expected, no two attacks will be identical; therefore, no two sets of structural repair taskings will be identical. Even during peac etime contingencies, engineer forc es must not get locked into a standard set of facility priorities and spend a lot of time on minor repairs to the detr iment of other more pressing requirements. For example, emergency repairs to a power generating plant may prove more important at some point in time than minor repairs to either an installation command and control (C2) center or other normally high-priority facility.

3.4.    Area Clearing and Safing Practices. Area clearing and safing are im portant considerations when accomplishing any type of repair, but they are es pecially important with regard to expedient repairs fol- lowing an emergency. Below are some common safety considerations and hazards that may be encoun- tered.

3.4.1.    Safety Considerations. Working smartly and safely is vitally important during area clearing operations. Disease-causing contaminants and structural damage could present s ome unusual health and safety problems for workers.

3.4.1.1.    Disease-Causing Contaminants. Some buildings affected by conventional attacks, hur- ricanes, or contaminated floodw aters have walls, insulation, fl oors, and ventilation systems that can become breeding grounds for disease. Build ing materials can exhibit a wicking ef fect that draws water into and up the walls—as much as 3 feet above the water line. Even if workers do not become contaminated while rep airing the facility, the occupants working in the buildings after- wards may quickly become seriously ill as the pa thogens grow and become airborne. If time is available, make sure that the work area and criti cal facilities are free of contaminants, even if it requires ripping out wallboard, fl oor covering, and insulation. Cons ider hosing off contaminants with clean water or disinfectant at the work site.

3.4.1.2.    Structural Damage. As emergency repairs are underw ay, efforts may grind to a halt should the building incur further consequential structural damage by wind and water after the ini- tial onslaught. When sheetrock becomes wet, it loses strength and becomes heavier. The additional weight and loss of stre ngth can cause further damage or coll apse. If repairs are delayed, provide temporary protection and early cleanup to avoid ad ditional damage. Shoring procedures that are covered in paragraph 3.6.may also be necessary.

3.4.2.    Hazards. Whether on or off base, not all hazards are identified and not all hazards are quickly cleared. Problems could arise when setting up for em ergency repairs even after first responders have been through the facilities.

3.4.2.1.    Electrical Hazards. Electrical wires are usually a problem following bomb damage, hur- ricanes, tornados, or floods. Th e wires are vulnerable and are easily knocked down. They can be especially hard to see at night and may not have been made safe by others. A generator powering a nearby work site can send power through damaged electrical systems and reenergize wires at the work site. When working in this type of environment, be on the lookout for loose wires and make sure that main power panels are off before entering a building for emergency repair. This is espe- cially important when working on metal roofs or metal structures situated near damaged electrical lines. The power distribution system damage depicted in Figure 3.2. is typical of what one might expect to encounter after a larger category hurricane.

Figure 3.2. Hurricane Damage on St. Thomas, Virgin Islands (1995).

3.4.2.2.    Gas Hazards. Gas explosions and fires can cause fa talities. Containers and tanks can be displaced by winds and floods. Compressed gas tanks and dr ums carrying chemicals are often found in facilities. These containe rs can easily penetrate buildi ng walls as they are moved about by high winds and flood waters. Be alert for leaking gas from tanks or ruptured utility lines, and pay particular attention to smells when around buildings. An extremely offensive, garlicky odor is usually associated with mercap tans, a class of sulf ur-containing compounds added to natural or bottled gas. Even moderate damage can turn deadly when leaking gas is involved. An ozone smell or a peculiar odor suggest ing that of weak chlorine may indi cate that there ar e arcing electrical wires.

3.4.2.3.    Biological Hazards. Biological hazards can be a problem after an attack. An example of this hazard would be a terrorist use of anthrax or smallpox. Natura l biological hazards are also a problem for civil engineers conducting emergency repairs after floods, hurricanes, and tornadoes. Hazardous wastes can also be a major problem afte r floods and other natu ral disasters. Floodwa- ters or debris may expose rot ting animal carcasses and sewage that contain pathogenic microbes, viruses, bacteria, and fungi.

3.4.2.4.    Animal and Insect Hazards. Live animals and insects can be just as dangerous as the effects of dead animals during floods. Animals, re ptiles, and insects often take refuge within buildings that have been damaged. Snakes and venomous insects can be especially problematic in coastal areas affected by floods and hurricanes.

3.4.2.5.    Asbestos and Lead Hazards. Exposure to asbestos and lead can be a problem, espe- cially when the work area has been badly damaged by an explosion or windstorm. Flying debris or blast waves can expo se enclosed areas of buildings wher e brittle asbestos wa s previously con- cealed. Previously encapsulated asbestos shingles, wallboard, plaster, insulation, or stucco can fracture and disperse asbestos fibers (see Figure 3.3.). While recent ba se control and removal efforts may limit exposure to asbestos on the in stallation, off-base facilities could cause serious exposure problems.

Figure 3.3. Examples of Asbestos Use in Construction.

3.5.    Debris Clearing Operations. A major disaster or enemy attack could generate vast amounts of debris (Figure 3.4.). When clearing debris from work areas and facilities, provide enough room around the facility to allow access for high-reach trucks, cranes, ladders, or scaffolding that may be required dur- ing the repair. Make sure utility and telephone cables are removed or completely isolated from the work area. Wires, cable, metal fences, pipes, and roofs can become energized and cause electrocution if con- tacted by hot power lines. At times it is safer to remove damaged building parts when it is extremely dan- gerous to repair the component. This is often the case with heavy hangar doors when dislodged from their tracks after an explosion or winds torm. Doors of this type normally require special equipment and train- ing to allow recovery or repair. However, large doors or smaller hangar door sections may be valuable as temporary replacement wall sections if equipment is available to safely move them. Always clear out haz- ardous materials and debris, especially wet debris. If immediate repairs cannot be made to walls or roofs with plywood, protect the area with tarps and/or plastic sheeting. Keep in mind that little adjustments can make the job much more manageable. For example, cleanup is easier when debris can be tossed through a blown out wall or window before repairs are made.

Figure 3.4. Debris Clearing After Hurricane Andrew at Homestead AFB (1992).

3.5.1.    Debris Removal Priorities. The priorities for debris removal will va ry depending on base mission and type of disaster. The Emergency Operations Center (EOC), or the on scene commander in the case of military response to a civilian emergency, assigns debris removal priorities. In the instance where damage is limited to a military complex, debris removal personnel should expect the EOC to assign the highest priorities to the areas most critical to the mission.

3.5.2.    Debris Removal Resources. As might be anticipated, the type of equipment required to clear an area is related to the size and amount of debris. Large pieces of wreckage will necessitate the use of heavy equipment such as bulldozer s and cranes. If equipment is s carce, areas with lar ge amounts of smaller-size debris may be cleared with hand tools. The following equipment items can be effective in debris clearance operations.

3.5.2.1.    Crane. For removing extremely large chunks of debris, a crane may be the only suitable piece of equipment. A crane can clear destruction on upper floors of a structure beyond the reach of a excavator or front-end loader.

3.5.2.2.    Bulldozer. A bulldozer has the power to push large pieces of debris out of an area and can quickly clear large areas of smaller debris (see Figure 3.5.). One skilled dozer operator can clear an area that would require several hours of labor if done by hand. However, bulldozers may be in short supply if runway repair is required.

Figure 3.5. Debris Clearing After Volcano Eruption in the Philippines (1991).

3.5.2.3.    Front-End Loader. Front-end loaders are especiall y useful in loading debris on dump trucks and other vehicles for removal from the site. They al so are adequate for clearing paved areas and streets of large amounts of small debris.

3.5.2.4.    Dump Truck. Dump trucks haul debris to disposal sites; however, after an attack, like bulldozers, they are essential vehicles in airfi eld damage repair activities and may be available only in limited numbers for debris removal. Other suitable vehicles, such as cargo trucks and trac- tor-trailer units, can sometimes substitute for them.

3.5.2.5.    Sweepers. Once larger debris is removed from an area, street sweepers are employed to clear smaller items from aircraft operating surfaces and primary access streets. If sweepers are not used, small metal items left on ro adways and working areas can cause tire damage to equipment involved in cleanup operations. Time spent repairing and replacing flat tires on these vehicles only serves to further delay the overall recovery effort.

3.5.2.6.    Towing Devices. Steel cable, chains, hooks, and similar items can be fashioned into tow- ing devices for debris removal.

3.5.2.7.    Hand Tools. Various types of hand tools are useful in debris cleara nce. Chainsaws and axes can be used to cut fallen tr ees into smaller sections for easier removal. Shovels are useful in loading smaller debris on vehicles for transport to a disposal site. Brooms and rakes can be used to clear surface areas of scattered debris.

3.5.2.8.    Manpower. The amount of CE manpower required to clear an area of debris will be based upon the availabilit y of the labor -saving equipment discussed in th e previous paragraphs. Obviously, if mechanical equipm ent is available, fewer person nel will be needed for cleanup. However, personnel assigned to cleanup detail must be skilled in the operation of equipment. Less equipment means a greater number of persons required, but their skil l levels need not be as high. During recovery operations on a military installa tion, in all likelihood, the EOC will task other installation agencies, whose post-attack missions may not be critical to aircraft generation, to sup- ply augmenters for debris removal efforts. In such instances, CE personnel will have to supervise these individuals during debris removal activities and provide them with necessary tools and pro- tective gear such as gloves. Also, remember the augmentees may not be cognizant of the dangers involved with debris removal nor be trained in explosive ordnance reconnaissance; therefore, their taskings should be assigned with these limitations in mind.

3.5.3.    Debris Removal Operations. The debris removal operation is dictated by available equip- ment, manpower, and common sense. In the period immediately following a disaster or enemy attack, the EOC or on scene commander will make decisions regardi ng how debris removal operations should proceed. Debris in nonessential areas will be left until additional re sources become available unless it hampers recovery operations or poses a sa fety hazard. Personnel will be assigned debris clearance tasks, and equipment will be allocated on a priority basis.

3.5.3.1.    Removal Preparations. This step consists of establis hing debris removal crews, posi- tioning equipment for removal activities, attaching cables and other devices to lar ge pieces of debris, breaking or cutting up lar ger debris pieces for ease of removal, and similar actions. Any debris salvageable for recovery operations should be set aside.

3.5.3.2.    Removal and Disposal. Under certain circumstances, the debris may be pushed into cra- ters, or prepared holes, and buried. When debris is not buried orotherwise disposed of at the scene of destruction, it is moved to a central location where it is loaded into dump trucks or other vehi- cles for transport to a remote location for burial or burning. The local environmental flight should be consulted before establishing any landfill or debris-burning operation.

3.6.    Structural Shoring. Once debris has been removed and safe access is assured, the first concern in structural repairs should be shoring any weakened areas to restore a mi nimum degree of structural integ- rity to the facility. Immediately after an attack or natural disaster, there may not be time to make a detailed engineering analysis on structural soundness. Instead, rely on field expe rience, facility appearance, com- mon sense, and instinct. If a facility appears beyond repair, demolition is probably in order. On the other hand, once it is determined to “save” a facility and the areas in need of repair have been identified, there are numerous shoring and patching repair options available. Most require relatively common engineering materials readily available on base or from off-base vendors. Examples include guying, bracing, jacking, splinting, tension ties, stitching dogs, and welding.

3.6.1.    Guying. Guys are usually fashioned from wire rope and tensioned by turnbuckles, if available. Guy wires are commonly found providing stabilizing support for power poles and tall antennas. Guys are normally installed to function in opposing pairs to pr ovide lateral restraint from such forces as wind or ice loading. They are particularly effective when damage has been sustaine d to end walls or sidewalls, yet roof members have been essentially untouched. Depending upon the situation, they can be installed either inside or outside a facility. The number of pairs required will depend upon the situ- ation at hand, based upon the size of the facility being shored and extent of damage sustained.

3.6.1.1.    Although a number of dif ferent wire rope fittings are avai lable commercially, by far the most common means of attachme nt of wire rope guys is the use of wire rope clips ( Figure 3.6.). When properly installed, clips can provide up to 80 percent of the rope’s strength. The size of the wire rope dictates the number of clips used and their spacing. A good rule of thum b is to use a minimum of three clips spaced about 3- 3/4 inches apart for 1/2- or 5/8-inch rope, and four clips spaced 4- 1/2 inches apart for 3/4- or 7/8-inch rope. These st andard practices prevent kinking of the rope and fraying of the cable due to friction when it is connect ed to a turnbuckle or other attachment. Also, note how the clips are attached to the rope. The bend of the U-bolt compresses the dead end of the rope, whereas the clip compresses the live end of the rope. The live end of the rope leads back to the structure that is being guyed.

Figure 3.6. Installation of Wire Rope Clips.

3.6.1.2.    Figure 3.7.illustrates a typical guy wire connectio n to a structure. The wire rope is attached to a turnbuckle that is attached to the building. This particular example shows a connec- tion to a steel beam using a beamclip. A beam clip ismerely a C-shaped connector that can be fab- ricated in the shop, if necessary. Other connections to a structure are possible using eye bolts and even wrapping the rope around the structural member to be stabilized. Note the use of the 2″ x 4″ board as a brace to prevent the guy wire from twisting as the turnbuckle is tightened. If an external guy is to be used, one end of the guy must be connected to a solid, immovable object, commonly referred to as a “deadman.” The deadman can be a nearby foundation, another part of the structure to be guyed, screw-anchors similar to what linemen use for pole guying, or even a piece of unser- viceable equipment, provided it is heavy enough.

Figure 3.7. Typical Guy Wire Connection to a Structure.

3.6.1.3.     As mentioned earlier, guys can be in stalled either internally or externally. Figure 3.8.

illustrates an internal configuration. Keep in mind that guys must betightened in pairs and concurrently to avoid placing too much stress on the stru cture’s frame at any particular point. However , caution must be used to prevent overtightening; the intent is to take a ll the sag out of the wire ropes.

Figure 3.8. Internal Guy System.

3.6.1.4.    The external guy configuration is also installed in pairs (see Figure 3.9.). The major dif- ference is instead of using the structure itself as the end points for the guys, external anchors or deadmen are used. The stabilization effect is essentially the same.

Figure 3.9. External Guy System.

3.6.2.    Bracing. Braces are compression members usually made of structural steel and heavy timbers (Figure 3.10.). Like guys, they can be installed eitherinternally or externally. Depending upon the sit- uation, they can be placed in opp osite pairs or used individually . Regardless of the method used, ensure adequate connections to the struct ure are made. If not well attached, the probability that the bracing will slide out of position is great, risk ing further facility damage or collapse. Footings for bracing require the same attention; they must be of sufficient mass so they will not move when force is applied. Do not expect a brace that is just shoved into the ground to hold. If necessary , build an expedient footing out of rubble, heavy metal, or timber if another part of the structure’s foundation, or the foundation of an adjacent building is not available.

Figure 3.10. Typical Brace Configuration.

3.6.2.1.    In most cases, braces will have to be installed in pairs, as shown in Figure 3.11. Like guy wires, more than one pair of braces may be required. This will be an on-site decision, generally driven by the size of the building being shored and severity of damage incurred.

Figure 3.11. Externally Opposed Braces.

3.6.2.2.     Internal braces are depicted in Figure 3.12. and are also normally installed in pairs. Remember, braces must be firmly attached to the facility to prevent slipping out of position when pressure is applied.

Figure 3.12. Internally Opposed Braces.

3.6.3.    Jacking. Guying and bracing usually are used to st abilize a facility from lateral movement, keeping it from moving side to side. In some cases, the structural integrity of a facility may be jeopar- dized due to damaged structural me mbers that are more directly affected by vertical loads—in other words, the effects of gravity. In such situations, there may be deflected or cracked beams/girders that need vertical support or damaged co lumns that will eventually need replacement. Shoring jacks help provide expedient solutions for these types of problems.

3.6.3.1.     Shoring jack s are placed immediately under the point of deflection, or adjacent to the damaged column, and extende d until they are firmly wedged into position ( Figure 3.13.). Any debris around the base of the jacks must be cleared away so that the jacks are positioned squarely on the facility floor. While not shown in the figure, it is also advisable to brace the jacks once they are in position. This can be accomplished by welding two steel plates on the jacks at 90 degrees to each other. The plates should have 3/4-inch holes drilled in them. Standard 2″ x 4″s are then bolted to the plates at one end and nailed at the other end to short pieces of 2″ x 4″ stock that have been attached to the floor of the facility using explosive actuated fasteners or suitable threaded concrete fasteners.

Figure 3.13. Shoring Jack Installation.

3.6.3.2.    In most cases, shoring jacks will be in short supply and too valuable to leave in damaged facilities. An alternative to leaving the jacks is using timbers as supporting members, as shown in Figure 3.14. Wood and timber are extensively used to shore damaged structural components because of their availability and economy. A variety of elemen ts can be employed, ranging from tree logs, sawed timbers, and utility poles to industrially made items with different cross sections, such as planks, boards and beams. The procedures for installing t imbers are similar to jacks, but are somewhat more manpower intensive. After clearing debris from the work area, a shoring jack is placed immediately adjacent to the location where the timber is going to go. Th e jack is then raised until it reaches the desi red height, or it can no longer be extended. Measure the distance from the top of the jack to the floor and cut th e timber 1/2-inch shorter than the measurement. Once cut, the timber is raised into position and several wedges are pounded into the 1/2-inch gap between the top of the timber and the damaged b eam; this secures the timb er into position. The shoring jack is then lowered and removed. The final step is to brace the timber in two directions, similar to what was done earlier with nails and 2″ x 4″ stock.

3.6.3.3.    Timber shoring can also be used for expedient repair of damaged load-bearing walls with openings, such as windows or doors. The use of timber to take the vertical load from a damaged masonry pier between tw o windows is shown in Figure 3.15. Note that bracing is used between the vertical timbers in each window opening. Th is common construction technique increases the efficiency of the timbers by reducing their potential for buckling under any increases in load. Also, spreader beams have been placed at the top and bottom of the ti mbers where they meet the win- dow frames. These beams spread the vertical load over a larger surface area, decreasing the chance of punching through or sh earing the window frame. Spreader beams can be made from planks, boards, or even steel plates. The wedges shown are used to secure the vertical timbers in position. One final note concerning the us e of timbers; if heavy timbers are not readily available, be resourceful. Other facilities that have been damaged beyond repair may contain salvageable tim- bers. Also, consider nailing, gluing, bolting, or banding 2″ x 8″ or 2″ x 10″ stock together to form usable substitutes.

Figure 3.14. Timber Column Use.

Figure 3.15. Support of Damaged Load Bearing Walls With Openings.

3.6.4.    Splinting. Another method of providing basic structural integrity involves the splinting of col- umns, particularly the reinforced concrete type, that have not been seriously damaged but show signs of cracking or minor fracturing.

3.6.4.1.     One te chnique involves “sandwiching” the damaged column between two steel plates connected by threaded rods. The plates have sl otted holes so they can be fitted to various sized columns. In this repair, splints are placed around the column at the location of the crack(s) to pro- vide a lateral restraining force (see Figure 3.16.). If cracks are at several locations on the column, multiple splints can be used. This repair is preferable to column replacement when a damaged col- umn is still capable of carrying a significant load, because it requires less manpower and is a faster repair. However, if a column is severely damaged and appears near the point of collapse, column replacement using jacks or timber supports should be used.

Figure 3.16. Steel Plate Splint.

3.6.4.2.    A second splinting technique involves placing angle iron at the corners of a damaged col- umn and connecting the angles with steel straps (see Figure 3.17.). Steel plates should be provided at the ends of the angles to a void load-bearing problems at the bottom of the column whe re it is attached to the slab.

Figure 3.17. Use of Steel Angles at Corners of a Damaged Column.

3.6.4.3.    A third method of splinting again uses angle iron at the corners of the damaged columns, but the angle irons are joined together with wire rope or similar cabling (see Figure 3.18.). One end of the wire rope is welded to the top of one of the angles, and the rope is tightly wound around the column. The other end of the wirerope is welded to one of the angles at the base of the column. Additional welds may be made at various points to better secure the cable to the angle iron.

Figure 3.18. Use of Wound Spiral to Repair Column.

3.6.5.    Tension Ties. Some facilities at overseas locations are essentially all reinforced concrete con- struction. In such cases, slabs and beams will be of unitary construction, meaning that they are formed, reinforced, and poured as a single unit. After an attack or na tural disaster, some of the slabs and beams may develop minor cracki ng. Tension ties are a method of providing a compressive force on the slabs and beam s that aids in th e prevention of further cracking (see Figure 3.19.). For slab repair, a threaded rod is anchored to the beams on both sides of the cracked area of the s lab. For beams, anchor plates are bolted to the beam on both sides of the crack and a threaded rod is placed parallel to the beam, connecting the two anchor plates. Tightening the nuts on the threaded rod induces a compressive force into the beam or slab, thereby restricting further cracking.

Figure 3.19. Tension Ties.

3.6.6.    Stitching Dogs. Yet another method of restoring structur al integrity into a cracked concrete slab is the use of “stitching dogs.” These dogs are steel bars, normally rebar , formed into a U-shape and placed over the crack, rather like staples, as shown in Figure 3.20. The dogs should be of random length and variably spaced along the crack. The hol es that the dogs are inse rted into must be well grouted to ensure a tight fit.

Figure 3.20. Stitching Dogs.

3.6.7.    Welding. Welding steel sections back into place to restore the stability of a steel framework is a common shoring meth od. Welding repairs will usua lly be limited to a relati vely small section of a facility. To attempt more than this as an expedient repair will take too much time and ef fort. For the most part, such repairs will involve erecting scaffolding, positioning steel plate and structural shapes, and accomplishing the welding.

3.7.    Expedient Repair of Damaged Facilities. Once basic structural integrity has been restored through structural shoring, steps can be taken to protect personnel and essential equipment from the elements. This usually involves patching hol es in walls, roofs, and floors. Before expending resources to patch these holes, determine if ur gent, immediate patching is required. Local climate and prevailing weather are major factors. If the weather i s warm and rainfall is not a detrimental factor , some openings may be left exposed temporarily without significant impact. On the other hand, if patching is required, there are sev- eral different types of materials and expedient techniques that can be used.

3.7.1.    Roof Repairs. It is important to recognize that some roofs and support sy stems perform vari- ous functions. While some are simply a weather cover, others act as part of a structural frame or dia- phragm. Analyze failed sections and holes in the roof to determine the needs for eme rgency repair. Initial efforts must focus on safety. Ensure that bracing and shoring are adequate. Secondly, eliminate hazardous hanging materials (i.e., lights, wires, cable trays, mechanical ducts, etc.) below the roof and assess the extent of damage to the roof support system. The third and any subsequent efforts are to cover the hole, replace damaged sections of roof covering, and strengthen the support system as nec- essary.

3.7.1.1.    Damage Assessment. Once the emergency has subsided, inspect both the top and bottom portions of the roof to make su re that the areas are sound. Be aw are that even though roof struc- tural members and the deck are intact, emergency repairs may still be needed. One example is that even after hurricane winds subside, persistent rains can cause severe damage or building collapse. Many roofs are covered with insulation boards. High winds can leave the decking intact but blow off felts and expose insu lation boards. Some insula tion boards soak up rain like a sponge. The additional dead load from the water-soaked insulation, as well as ponding of trapped water, can collapse structures, especially warehouses and large hangars. If the supporting members are dam- aged, shore and brace the trusses and repair damaged supports.

3.7.1.2.    Fire-Damaged Roofing Components. Fire-damaged wood struct ural members must be checked for structural integrity. Scrape the ch arred wood off the member in various sections to check for the extent of damage. Fire-damaged wo od can remain in place if it retains most of its structural integrity. The amount of remaining strength will depend on the extent of charring or exposure to high temperatures. There is no defini tive, in-place test to determine if fire-damaged wood is still structurally sound. An engineering test and analysis are normally required. If the structure was modified af ter construction, such as installing an overhead rail, then a structural analysis is needed to determine if fire-damaged members are adequate. Charred wood should only be used if at least 90 percent of the wood cross section is not charred; and charring itself does not extend more than 1/16 inch into the wood. Emer gency repair of fire-damaged trusses normally involves scraping off the charred material and sistering a similar piece of wood onto the damaged section, splinting the damaged area between two sound pieces of wood, using gusset plates (see Figure 3.21.), or using a combination of these procedures.

Figure 3.21. Gusset Plate Repairs.

3.7.1.3.    Weather Tightness. Once the structural integrity is assured you can begin returning the weather tightness to the structure. From an expedient aspect, it will be difficult to completely seal off the building from weather, but most of the i ll effects of bad weather can be kept out. Keep in mind that many roof systems are interchangeable . An example is that metal and wood roof sys- tems can be used with wood, metal, or precast concrete buildings. Sheets of plywood can be nailed over the opening. Sheet metal, plas tic sheeting, and even canvas can be used in lieu of plywood. For flat roofs, sheets of plywood can be fabricated into a patch a bit larger than the hole and nailed in place. If the roof isconcrete, explosive actuated fasteners or suitable threaded concrete fasteners could be used to att ach the plywood patch. If av ailable, rolled roofing ca n then be nailed to the patch for added weather protection. Figure 3.22. shows personnel providi ng expedient roof pro- tection, in the form of plastic sheeting, on a h ousing unit at Homestead AFB after Hurricane Andrew’s assault in 1992. Once any covering is in place, positive drainage must be maintained to divert rainwater and prevent po nding. This could involve stacki ng sandbags above the repair to divert the water or changing the sl ope at the repair itself. For lar ger areas, raise the center of the tarp or sheeting to divert water.

Figure 3.22. Using Plastic to Cover a Damaged Roof.

3.7.1.4.    Metal Roof Repair. Metal roofs are repaired the same way as metal wall systems. When possible, remove the dama ged surface material and replace wi th new or cannibalized material. Overlap the good metal roofing wi th the replacement metal roofi ng by at least a matching co rru- gation or rib section. Catch as many purlins as possible for support and t ack in place with sheet metal screws along the edges. Use caulk or construction adhesive on the upslope side for addi- tional water protection. For lar ge holes where purlins are too badly damaged to allow fast repair, and where reuse and imme diate coverage is required, expediently pa tch the hole w ith similar materials, but provide at least 24 inches of overlap to distribute loadings. Add purlins later as time allows.

3.7.2.    Wall Repairs. For the most part, wall repairs are similar to roof repairs, except they should be somewhat easier since the requirement to lift all materials to ro of height is eliminated. Damage to walls can be covered with standard materials such as plywood, sheet metal, tarpaulins, and plastic sheets (Figure 3.23.). Before beginning a wall repair , ensure the structure is st rong enough to with- stand pounding from additional winds when using tarps or plastic sheeting. Shore and brace the struc- ture as described previously in paragraph 3.6., if required. Secured tarps can provide good protection from rain and can withstand greate r wind loads than plastic sheeting. Note: Usually large tarps and high-strength plastic sheets must be special ordered but are generally available as a construction mate- rial item. Coordinate with federal and state emergency management officials or MAJCOM personnel to obtain large tarps and sheeting. For overseas humanitarian deployments, the US Agency for Inter- national Development (USAID), Office of Foreign Disa ster Assistance (OFDA) can often provide special sheeting for shelters.

Figure 3.23. Temporary Tarpaulin Protection.

3.7.2.1.    Plastic Sheeting Protective Techniques. When plastic sheeting is used to cover a hole, size the nailing strips and plastic based on the si ze of the hole. Normally , the required materials are: nailing strips that are at least 1″ x 2″ furring strips (or 12-gauge metal strips that are 1″ wide), plastic sheeting that is at least 6-mil plastic or reinforced sheeting (10-mil plastic or plastic with woven fiber is preferable), and fasteners of sufficient length to penetrate the sheathing (or at least 1- 1/2 inches into the stud). Avoid black, recycled plastic sheeting if the repair will be exposed to harsh elements for more than a month due to the hi gh rate of deteriorati on. Use nails, staples, or screws in wood and self- tapping metal screws to fasten into metal siding. To accomplish the repair, wrap plastic sheeting around nailing strips and nail the strips around the hole as a rectangu- lar frame to provide a tight plastic surface. When possible, provide 6 to 12 inches of plastic over- lap around the edges of the hole. For holes in plywood (or other nailable substrate) cut the nailing strips 12 to 24 inches wider than the hole and cut the plastic sheeting yet another 24 inches wider. For holes in a non-nailable substrate, locate the nailing strips over the closest undamaged wall-framing studs. Cut the plastic sheeting 24 inches wider than the nailing strip. Wrap 12 inches of plastic around both the top and bottom nailing strips. When installed, the plastic should be flat against the building with the wrapped nailing strip on the outside. Position the strips and fasten in place to the wall (or studs for non-nailable surfaces), stretching tight vertically (see Figure 3.24.). Note that both plastic sheets and tarps only provide protection against the elements. More substan- tial structural repairs are often necessary.

3.7.2.1.1.     If there are no intermedia te studs to nail into for s upport, use adhesive and tape to secure the top and bottom edges. If there are damaged intermed iate studs, sister new studs to the damaged studs to allow nailing strips to be fastened.

3.7.2.1.2.     Repair any miss-cuts or tears in the plastic with flexible duct tape. Use caulk to fill in larger gaps between the nailing strips and wall surface. For metal skin walls with deforma- tions, use expanding foam to fill in gaps as necessary between the metal and the nailing strip.

Figure 3.24. Typical Plastic Sheeting Wall Repair.

3.7.2.2.    Emergency Wall Repairs on Wood Frame Structures. Wood-framed walls are typi- cally the easiest wall systems to repair. Depending on the size of the hole, the repair may be made by replacing the damage d area in kind, repl acing a wall section, or providing a structural or non-structural patch. Explosions, projectiles, or debris can create similar damage in wood-framed walls. The repair requirements will vary by the size of hole, location, a nd wall function. Smaller holes with little damage to framing members can usually be fixed with a sheathing material (ply- wood, fiberglass, metal sheet, etc.) or plastic sheeting. Plywood or Oriented Strand Board (OSB) sheets are normally used. Holes larger than 3 feet in diameter usually require some reframing and new plywood/OSB. Still larger holes usually require the wall s ection to be replaced with new framing and plywood/OSB on the outside of the wall. If the damaged wall is a shearwall, a cross wall that provides lateral support, or a load-bearing wall, a structural frame wall having plywood on both sides may be required.

3.7.2.2.1.     Small Hole Repair. Use plywood or OSB sheathing to repair small holes (less than 3 feet in diameter) when the substrate is nailable. If possible, provide at least a 6-inch overlap over the undamaged siding. If mo re weather protection is need ed than provided by plastic sheeting, use sheathing. When the substrate is not nailable, cut the sheathing to fit between the closest studs on both sides of the hole. Position sheathing over the hole and fasten into a stud or nailable substrate. Be sure to caulk alongthe edge of the sheathing before fastening in place.

3.7.2.2.2.     Large Hole Repair. Remove damaged framing for larger holes, but be particularly careful around any load-bearing joists, beams, or wall top plates. Replace damaged or missing framing and blocking. Where sheathing is missi ng and framing is damaged, the wall usually requires repair or replacement of damaged framing and new sheathing. After shoring and brac- ing adjoining walls and ceiling, replace any missing studs and top and bottom plates. Attempt to maintain normal stud spacing at 16 inches on center. For partially split or gouged studs (i.e., 60 to 80 percent of the damaged stud cross section remains) and where some sheathing is still present, sister another stud to the damaged stud to strengthen it. Apply construction adhesive between the damaged stud and new stud for addi tional strength. To add strength to walls that must withstand additional wind lo ads, apply construction adhesi ve on stud surfaces and then nail the members together.

3.7.2.3.    Emergency Wall Repairs on Masonry Structures. Emergency repair of masonry walls is usually more time-consuming, strenuous, and equipment and material sensitive than emergency repairs to wood walls. Masonry walls are usually block and/or brick; however, masonry building- scomposed of rock and mo rtar walls may be encountered at some overseas locations. Use extra caution when performing emergency repairs on masonry walls. Failed masonry walls are normally more dangerous to work with than most other walls for seve ral reasons. This added danger is caused by factors such as the increased dead weight of the building materials, the brittle nature of masonry products, and the limited ab ility to determine the actual extent of damage by simply viewing the apparent damage. In fact, it may not beknown how or even if the wall is reinforced or what is holding the cracked areas together.

3.7.2.3.1.     Damage Assessment Considerations. Consider the following when assessing masonry wall damage. While a crack may appear to be small, the wall may still fail if there is inadequate reinforcing steel to hold the crack together. Reinforcing steel is us ually in select cells. Determine if a crack crosses reinforced cells and if the cells are still solid. If the cells do not contain reinforcing steel, determine if the crack is being momentarily held in place by fric- tion from dead loads. If such is the case, a small shift in the weight of a structure or ground tremors (i.e., seismic shaking from nearby move ment of heavy equipmen t) can cause release and catastrophic collapse. Keep in mind that re moval of debris, rain, snow , or wind can also cause shifting in multistory structures and subsequent collapse. Two additional factors associ- ated with masonry walls that must be assessed include determining if the wall can be shored to maintain lateral support when pilasters are damaged and deter mining if the wall’ s floor/roof attachments are damaged or have failed.

Figure 3.25. Examples of Sheathing Damage.

3.7.2.3.2.     Masonry Wall Variations. Emergency repairs to mas onry structures usually depend on whether the wall is a structural wall or a non-stru ctural infill wall ( Figure 3.26.). Structural walls can be infill walls that provide lateral support or shearwalls built into a con- crete or steel moment frame building. Also, structural wall s can be supporting walls (and pilasters) that provide lateral and vertical support for the roof and other floors. Non-structural walls are usually constructed as infill walls that have wall ties to flexible frames, or they may use tracks or of fset walls that extend past the exterior frame and wrap around it without pro- viding lateral support. If a structural wall is damaged, emergency shoring and bracing may be required along with repair. Once strengthened, th e wall should be closed up with injection grout or some other means of confinement as discussed in this chapter. Emergency repairs for non-structural walls depend on the da mage. Typical repairs usually involve removing and replacing damaged material and patching the open area with appropriate sheathing.

Figure 3.26. Damaged Brick Infill Wall.

3.7.2.4.    Small Hole Repair in Structural Walls. The simplest emergency repair to a masonry wall is repairing a small hole that has been punched through the wall involving no damage to the rest of the structure. Usually , this will occu r from debris being thrown through the wall from an exterior blast or high winds. The repair method for small punched holes in masonry structures var- ies according to the type of wall involved. Th e emergency repair method for small holes cleanly punched through a non-structural masonry wall, where only a few blocks are missing, is to simply fasten a patch of wood sheathing over the hole. Cut a sheet of sheathing (plywood or OSB) that is large enough to extend several in ches past the next unda maged blocks’ grout joints around the hole. When positioning the patch on the outside of the wall, apply construction adhesive to the edges of the sheathing. Next, drill holes through the sheathing and into the undamaged grout joint (or a block with a filled cell); secure the shea thing in place with bolts , washers, and lead or expanding anchors. Do not use th is repair method if there are loose blocks or cracks around the hole; rather, tie the wall together with sheathing on both sides. When only a block or two are miss- ing, it is usually easier to knock out the damage d material, square up the opening to size, and fill the void using new blocks and a fast-setting cement or epoxy grout mortar (see Figure 3.27.).

Figure 3.27. Correcting Damage With New Material.

3.7.2.5.    Large Hole Repair in Structural Walls. Structural masonry walls with lar ger holes (i.e., larger than about five blocks high and four blocks wide) orfailed sections are very dangerous (see Figure 3.28.). It is usually better to shore and br ace the roof or floors above the failed area and then work somewhere else in the facility. However, moving to another section of the building should not be attempted until th e extent of the structural dama ge has been thoroughly analyzed. Failed sections in one part of a masonry building can often lead to a progressive collapse in the rest of the structure when wind, rain, vi bration, or shifting loads are involved. Figure 3.29. is an excellent example of a progressive structural failure after an earthquake. There are few options for making emergency repairs for larger holes in structural masonry wa lls. For a wartime repair of a larger hole in a shearwall or support wall, shore and brace the area around the wall, square up the hole, provide necessary bracing, and cover the hole. Leave the shoring in place if there will be continued blast or seismic shaking; cribbing is more stable than using a single support post. After shoring the area, square the hole, brace the hole with double 2″ x 8″ headers and side braces, and use double 2″ x 4″ cross bracing. Cover over each side with 1 or 2 layers of 3/4-inch plywood (depending on the expected shear loads). Cut sheets to run horizontally, and allow at least 8 inches of overlap onto good masonry . Position sheets and drill holes th rough the masonry to align with the holes in the plywood. Tie together with threaded rods, wa shers, and nuts. When possible, use 2″ x 4″s between opposing bolts to prevent the tie rods, washers, and nuts from tearing through the plywood.

Figure 3.28. Extensive Structural Wall Damage at Homestead AFB. (1992)

Figure 3.29. Progressive Structural Damage in Guam (1999).

3.7.2.6.    Structural Wall Confining. When broken blocks cannot be replaced for a small hole in a structural masonry wall, confin ing the wall is a safe option. Th is repair should be limited to small holes with 7 or 8 blocks missing and where there is no extensive cracking around the hole. Use at least 4- or 3-gauge sheet steel (i.e., about 1/4-inch thick) on both sides of the hole. Cut the steel to provide about 8 inches of overlap between the steel and the undamaged block. Drill through the sheet steel about 4 in ches from the edges in the corn ers and midpoint on each side. Next, drill through the masonry so it will align with the holes in the sheet steel. Next, run a bead of construction adhesive around the hole on both sides before fa stening the sheet steel together with threaded rods, washers, and nuts (see Figure 3.30. graphic sequence).

Figure 3.30. Masonry Wall Confining Sequence.

3.7.2.7.    Large Hole Repair in Non-Structural Walls. Non-structural walls with lar ge holes (i.e., up to about five blocks high and four blockswide) can usually be repaired with a sheet of ply- wood, a couple of 2″ x 8″ braces , and a header. Knock out or sa w-cut loose block on the top and sides of the hole to provide fairly straight edges (i.e., square up the hole). Cut one or two 2″ x 8″s for a header to fit the top of the squared hole (if overseas and metric blocks are used, use a wider header or add 3/4-inch plywood cut as wide as the block and nailed to the top of the header). Next, cut two side braces about 1/8 inch longer than the distance from the bottom of the hole to the bot- tom of the header and place one end of the braces at the bottom of the hole on each side and drive the top of the braces in place to hold up the header . Once in position, toe- nail the top of each header. Lastly, cut sheathing and fasten in place in the same manner as described for covering a small hole. If desired, and for add itional rigidity, apply 1/2-inch sheetrock on the inside facing. Additional expedient masonry wall repair procedure options, such as pressure injected epoxy and structural steel bracing, are provided in the Expedient Structural Repair Course on the Air Force Civil Engineer Virtual Learning Center web site at https://afcesa.csd.disa.mil.

3.7.2.8.    Crack Repairs on Reinforced Walls. When replacing a reinforced masonry or concrete wall is not feasible, an a cceptable repair is to f ill the cracks with a struct ural grout or epoxy. In most cases, epoxy injection works best (see Attachment 2, Crack Repair Using Epoxy Injection Method). The epoxy injection method can be used to repair cracks as narrow as 0.002 inch if the reinforcing steel has not been stre ssed beyond its elastic limit. If necessary, seal the top of the crack with the same epoxy troweled in place or use metal plates. This type of repair generally con- sists of drilling holes at close intervals along the cracks, in some cases installing entry ports, and injecting the epoxy under pressure . However, for small cracks, cartridges can be used with hand- guns (see Figure 3.31.). For massive structures, an alternative procedure consists of drilling a series of holes, usually 7/8 inch in diameter, that intercept the crack at a number of locations. Typ- ically, holes are spaced at 5-foot intervals.

Figure 3.31. Epoxy Application.

3.7.3.    Window Repair. In an expedient sen se, there are no t too many fixes fo r damaged windows. Attempting to replace glass is much too long an ef fort and during a conflict or earthquake, is almost self-defeating since it will probably all be lost again in the next attack or aftershock.

3.7.3.1.    Repair Options. Normally, placing plywood over the window opening is sufficient. If the facility must remain occupied and requires da ylight, then rigid plasti c sheets can be used to maintain a visible opening. Plexiglas sheets ar e usually used for this repair . Use polycarbonate sheets if additional protection is required. Either way, it is important to first bond the rigid sheet to the building using construction adhesive, and then clamp it to the building using a simple wooden or metal frame and screws.

3.7.3.2.    Repair Procedures. Do not drill or fasten through the sheets if there will be additional blasts or high winds. In stead, hold them in place with a wooden (or metal) frame. Cut the rigid sheets 2 inches wider and taller than the opening. Use 2″ x 4″s or 2″ x 6″s to frame the opening, sizing the frame to fit outside the dimension of the opening. Once the frame is configured, apply a continuous bead of construction adhesive to the edge of the opening to set and hold the sheet in place. Sandwich the rigid sheet between the building and the frame and clamp in place by fasten- ing the frame to the building with screws or other appropriate (removable) fasteners.

3.7.4.    Door Repair. Damaged door openings that must remain accessible for entry and exit are usu- ally shored and framed to keep the opening safe . To protect the opening against further damage from wind, weather, or blast forces, use expedient measures such as stacking sandbags at the opening. This is especially important when the wall is a structural wall and has been damaged.

3.7.4.1.    Repair Priorities. The first priority for an emergency repair of a door opening in a struc- tural wall is to maintain the wall’s structural integrity. Shore the opening at the top, bottom, and sides. Use spreaders at the top and bottom of the door to take the place of cross bracing. If blast or wind protection is required, use sandbags stacked at the entrance and along walls (see Figure 3.32.).

Figure 3.32. Sandbagged Entrance.

3.7.4.2.    Weather Tightness. If weather tightness and further strengthening are required, con- struct a separate door. Tack the door framework to the opening to avoid causing additional stress on any weakened structures. Make sure the conn ections to the building are relatively weak. Rely on sandbag berms or other expedient berm structures for protection against blast.

3.7.4.3.    Sliding/Roller Doors. Hangars, warehouses, and maintenance facilities are often critical facilities. Other than for hardened aircraft shelters, these types of fac ilities have doors that are quite vulnerable to exterior blast and high wind s. Typical hangar-type doors are bottom rolling (sliding doors), which have top guide tracks and bottom rollers on support tracks. Different types of large doors can be used on large facilities when blast protection is not a problem or when snow and ice are a problem. Lightwei ght doors are often used on newe r permanent or deployable han- gars and warehouses. Deployable hangars and some newer hangars, maintenance facilities, and warehouses may have vertical lift, clamshell, canopy, or folded-fabric lift (panel) doors.

3.7.4.4.    Heavy Metal Door Repair. Full metal, bottom-rolling doors that have come loose from their tracks usually cannot be expediently repaire d. Limit repairs to patchi ng holes. If the rollers and top tracks are not damaged, some doors can be jacked up and pushed back on tracks. The fol- lowing failures require door removal and/or track repair: (1) rolling doors come loose from the top rail; (2) the doors have fallen in ward from the top when wind or blast pressures have racked the building or collapsed the metal overhead track sy stem, (3) high winds or floods lifted or pushed the doors off the bottom track; (4) the door ha s hung up on the upper track and torqued the wall and supporting framework. Warning: When dealing with very lar ge metal rolling doors such as those on hangars, emergency repair is usually not feasible excep t by tra ined heavy repair teams supported by cranes and other sp ecial equipment. Also, check on the door and framing specifica- tions before considering the repair of top rail s using standard shapes of A36 (36,000-psi) steel. Large steel hangar door structures often use 50,000-ps i steel and special fittings. If an A36 struc- tural shape is used and the orig inal specification was for 50,000-psi steel, the door framing and tracks will be grossly undersized for the load.

Figure 3.33. Lightweight Fabric Hangar.

3.7.4.5.1.     Structural Repairs. Bent framing on these types of structures can usually be straightened, bolstered with additional pipi ng, or replaced with similar common materials. Also, damaged tracks can often be straightened or detached/cut out and replaced using similar materials.

3.7.4.5.2.     Surface Skin Repairs. Holes in lightweight rigid co mposite panels are usually repaired with a patch of 14-gauge sheet metal fastened over the hole. Use construction adhe- sive and sheet metal screws, screw-in shield s, or expanding sleeve anchors, whichever is appropriate. Fabric panel system s can usually be quickly repair ed. Coated fabric systems are used with many portable shelters, deployable hangars, and maintenance shelters. The most common coating is PVC-coated polyester. It is used with many clamshell-type structures and fabric hangars. Larger structures may use a tensile fabric design. Emergency repairs must maintain structural integrity of these larger structures. Emergency fabric repair kits are usually available from the manufacturer. If one is not available, cons ult with Fuel System Mainte- nance or Fabrication shops, as some of their shop methods and equipment are similar to man- ufacturers’ recommended methods and equipment. Depending on whether the material is a cover fabric or tensile fabric, there are usua lly two repair methods for fixing pierced fabric sections in walls and overhead doors: the Fabric Clamp and PVC-Coated Polyester Fabric sys- tem.

3.7.4.5.3.     Fabric Clamp Repair. Fabric clamp systems are most often used for folded fab- ric-lift doors ( Figure 3.34.). The steps involved begin with loosening screws on the fab- ric-clamp strips above and belo w the torn section. Next, cut th e repair fabric lar ge enough to overlap the tear by at least 2 inches on each side. Once t he repair patch is properly sized, extend the repair fabric under and between th e two clamp strips . Then, retighten the clamp strips, trim off excess material, and tack down the fabric edges with adhesive or double-sided tape. Lastly, trim off or glue together any l oose fabric that is under the patch and around the tear.

Figure 3.34. Typical Fabric Clamp Repair.

3.7.5.    Repair of PVC-Coated Polyester Fabric Systems. These systems are used with several gen- erations of shelters and hangars. T he manufacturer for each system usually provides repair criteria; however, if criteria are not readily available, follow the general guidance here. Repairs usually require either a heat-welded patch (with either a heat gun or bonding iron and a roller) or a solvent-welded patch (with solvent). For coated fabric systems that have a slick, Teflon-like coating on the exterior surface, patch the hole from the inside using a piece of fabric and adhesive. As with the Fabric Clamp method, work with Fuel System Maintenance and Fabrication shop personnel to repair these types of fabrics. Begin the repair by cutting and positioning afabric patch over the torn section. For tensile fab- ric systems that distribute load, cut the patch to extend at least 12 inches past each damaged edge, unless the manufacturer has othe r recommendations. For simple cover systems, cut the patch to extend 2 to 4 inches past each damaged edge. For heat-welded patches, provide heat between the fab- ric and the patch. Hold a piece of plywood on the inside surface and use the roller on the outside of the heated patch to roll the material together. Roll out air bubbles, keeping the temperature just under the point where smoke develops on the patch or the two fabrics will melt. When done properly, the result should look similar to that in Figure 3.35.

Figure 3.35. Typical Heat/Solvent -Welded Patch Repair.

3.7.6.    Cement and Sealer Fabric Repair. Other fabric-based deployabl e structures, such as the TEMPER tent and Medium/Small Shelters, are all sh eathed with a fabric outer covering over rigid framing. When damage to these units occurs, it is not always pos sible or practical to make sewn repairs. This is especially true when a tent is erected and the damage is minor. If a hole or tear is fairly small and it is not located near a seam, an edge, or hardware, a cemented patch or dab of adhesive can be used to repair the damage. Whena stovepipe shield is slightly damaged, sealer can be used to repair the damage. There are specific repa ir kits available that have been developed by each product manu- facturer to correct minor damage. T ypical repair procedures for minor holes and tears are described below.

3.7.6.1.    Small Hole Adhesive Repair. A dab of adhesive is used on a hole in a tent that measures 1/8 inch or less across. To seal a small hole, first use a wire brush to clean the area around the hole and raise the nap of the fabric. Next, simply use a small stick or paddle to put a dab of adhesive on the hole, working it into the fabr ic while being sure to bridge the damage with the adhesive to ensure a complete seal.

3.7.6.2.    Large Hole/Tear Adhesive Repair. Cemented patches are used to cover holes and tears that are more than 1/8 inch, but less than 4 3/4 inches across. Putting a cemented patch on a tent is similar to patching a bicycle tire. To apply a cemented patch (seeFigure 3.36.), first obtain the fol- lowing items (if not included in the repair kit): a ruler, chalk, wire brush, flat board, paddle, roller, tent-patching adhesive, and a piece of clean matching canvas. Ne xt, measure the damage and cut a round patch from a piece of matching canvas, making sure the patch is large enough to extend 3/ 4 inch beyond the damage in all directions. Th en, place the board under the damage for support. On an erect tent, another individua l will be needed inside the tent to hold the board against the damage. Center the patch over the damage and draw a circle with chalk around the patch, then remove the patch. Use a wire brush to clean the fabric and raise the nap of the material inside the circle and the patch itself. Now, position the patch facedown over the damage and use the paddle to coat the patch evenly with adhesive. Let the adhesive overlap the edge of the patch a little so that it forms a circle on the tent. Next, remove the patch, flatten outthe canvas and the edges of the hole or tear as much as possible and fill in the circle with a coating of adhesive. Let the adhesive dry, then apply a second coat of adhesive to the tent and to the patch. Now, wait 10 to 15 minutes for the adhesive to become tacky (test the patch by touching it). The patch is ready to use when it is sticky. Once the adhesive reaches this point, center the patch face up on top of the damage and press the two sticky surfaces together. Use a roller to press the excess adhesive and the air bubbles from under the patch. Roll first in one direction and then in the opposite direction. If no roller is available, use the can of adhesive as a roller. Be sure to tightly seal the can first. Lastly, dip the tip of one gloved finger in the adhesive and ru n the finger around th e edge of the pa tch to seal the edge with adhesive and prevent fraying. Note: With some fabric (e.g., TEMPER tents), large tears must be sewn together prior to theapplication of adhesive or sealer. Caution: Seam sealer and sol- vent are extremely flammable and contain toxic fumes. Do not sm oke or use seam sealer/solvent near an open flame. Use seam sealer and solven t with goggles and gloves. When indoors, wear a respirator, or use in an open, well ventilated area, aw ay from sources of combustion. Death or severe injury may result from explosion or fire. Inhalation of fumes may cause toxic sickness.

Figure 3.36. Large Hole/Tear Adhesive Repair Steps.

3.7.6.3.    Sealer Repairs for Small Holes and Tears in Stovepipe Shields. Holes and tears in stovepipe shields can be repaired with sealer. The kind of repair used depends on the extent of the damage, as described below. A layer of silicone sealer is used to repair holes or tears that measure 2 inches or less across. To make this repair, obtain cleaning materials, a dry rag, a can of silicone sealer (MIL-A-46106), and a pa ddle. Then clean and dry the da maged area thoroughly. Next, spread a 1/16-inch-thick layer of sealer on both sides of the shield, covering the hole or tear and at least 1/2 inch on each s ide of the damage. Smooth out the layer as evenly as po ssible. Brace the shield so that the sealer does not touch anything while it is wet, and allow the repair to dry for 4 hours on a sunny day with low humidity or 6 hours on a humid day. Do not move the tent while the sealer is drying.

3.7.6.4.    Sealer Repairs for Large Holes and Tears in Stovepipe Shields. A patch attached with silicone sealer is used to repair holes and tears more than 2 inches across in stovepipe shields. To make this repair (see Figure 3.37.), first obtain the following items(if not included in the repair kit): ruler, cleaning materials, a dry rag, a craftsman’s knife, a piece of matching patch material, a can of silicone sealer , and a paddle. Begin th e process by cleaning and drying the damaged area thoroughly. Next, measure the damaged area and cut a patch from material salvaged from a shield that could not be repaired, making sure that the patch is large enough to extend 1 inch beyond the damage on all sides. Now, spread a layer of sealer on either the pa tch or the shield and press the patch in place at once. Finally, spread sealer 1 inch over all edgesof the patch to eliminate fraying. Do not move the shield for 4 to 6 hours.

Figure 3.37. Larger Hole Sealer Repair.

3.7.6.5.     Additional details on fabric repair procedures can be obtained in the following docu- ments: FM 10-16, General Fabric Repair; T.O. 35E5-6-1, Tent, Extendable, Modular, Personnel (TEMPER); T.O. 35E5-6-11, Alaska Small Shelter System; and T.O. 35E-6-21, Californian Medium Shelter System.

3.8.    Conversion of Alternate Facilities. There may be some facilities which are damaged beyond expe- dient repair capabilities. If such a facility is vital to the air base mission, another facility must be con- verted to meet the uninhabitable faci lity’s role. To effectively convert another facility, engineers must be aware of the function of the destroyed structure. Equipped with this knowledge, potential alternate facili- ties can be evaluated in terms ofsize, utilities support, and other special functional requirements. To select or recommend the best facility for conversion, the base civil engineer (BCE) should consider two factors. First, what other structures on the installation come closest to meeting the requirements for an alternate facility? Second, how much work will be required to convert the facility to meet its intended use? If there are no special considerations, the structure meetin g the functional requirements and taking the least amount of time to convert should be selected.

Chapter 4

EXPEDIENT REPAIR OF WATER AND WASTE SYSTEMS

4.1.    Introduction. Timely repair of water and waste systems is essential after a disaster or enemy attack for obvious health, hygiene, and operational reasons. Since it is impossible to predict the extent of damage to these systems during a disaster or attac k, specific priorities need to be established after an incident. Facility priorities listed in base recovery plans are generally a s ound starting guide. However, the Emer- gency Operations Center (EOC) normally dictates repair priorities during emergencies. Bottom line—ser- vice to crucial base functions must be restored quickly. If necessary, some creative engineering and cannibalization of non-critical systems may be required to establish or keep priority water and sanitation systems operating.

4.2.    Overview. This chapter primarily focuses on exp edient water and waste systems repair. Addition- ally, gas line and POL system repa ir is briefly discussed. Although some expedient repairs to water and waste systems end up being permanent, most repairs are temporary measures that provide limited support for short periods. The topics presented in this chapter address expedient repair of water distribution, water treatment, water storage, expedient water sources, sewage disposal, gas line, and POL systems.

4.3.    Water Distribution Systems. Water is an important utility requiring quick restoration following a disaster or hostil e attack. Water systems normally have a high pr iority for repair due to fi refighting requirements, decontamination purposes, personal consumption, cooking uses, and both general and med- ical hygiene. The major components of any water supply system are source, treatment, storage, and distri- bution. Of these, the distribution network is the most extensive component of the installation water system and is where most expedient repairs are affected.

4.3.1.    Anticipated Damage and Effects. Subterranean construction pr otects the distribution net- work from certain types of disasters. Its widespread layout can make it more vulnerable to other emer- gencies.

4.3.1.1.     High wind associated with ahurricane or tornado is not likely to break underground water mains, but a major enemy air attack is almost certain to disrupt some part of the dispersed layout of the distribution network. Dama ge to the d istribution system is normally confined to pumps, valves, and water mains. Water mains may be broken in several locations resulting in easily recog- nizable leaks ( Figure 4.1.) as well as numerous hidden leak s producing delayed damage in the form of undermined streets or structures.

4.3.1.2.     A water system is easily contaminated wh en water mains and sewe rs in close proximity are fractured. If the water mains and sewers are on a steep gradient, sewa ge may enter the water mains with enough head to flow to the consumer s’ taps below. Contamination may result when broken mains reduce pressure within the system, heavy draft for firefight ing, valve closures, and supply failures occurring during enemy attack or sabotage. Contamination may also be caused by filth entering open mains through open ends or fractures during repair operations. The more com- mon diseases attributed to contaminated water are typhoid fever, cholera, and dysentery. Diarrhea may also be caused by contaminat ed water. An epidemic of any of these seriously hampers mili- tary operations.

Figure 4.1. Obvious Water Line Break.

4.3.1.3.     During periods of conflict, a retreating enemy or terrorists may deliberately contaminate water supply systems by placing bo ne oil, refuse, bodies, lubrica tion oils, or other materials in wells, springs, reservoirs, tanks, or the distri bution system. Consequently, measures should be taken to secure easy access points such as well points, pumping stations, and storage vessels.

4.3.2.    Expedient Repair Procedures. As soon as the situation perm its, work should be started on restoring water supply sin ce water supply systems ofte n have a higher priority in rehabilitation than other utilities. Time is normally a limiting factor during base recovery, and rapid completion of the job is by far more important than economy of labor , materials, and equipment. In making improvised repairs, any suitable material or equipment available is used to me et the immediate need. A repaired water main does not have to be l eak-proof to be functional. Expe dient repairs are improved as time and supplies allow. Water distribution systems include pipe from 1- 1/ 2 to 24 inches in diameter and may consist of PVC rigid plastic pi pe, steel, asbestos cement, cast iron, and ductile iron. Water pres- sure ranges from 60- to 120- psi. Most distribution lin es are considered repa irable and, therefore, efforts should concentrate on quicklyreestablishing major feeder lines. As a general rule, system com- ponents, such as pumps, hydrants, valves, and purifica tion units, are not considered expediently repairable due to the time required to accomplish a fix. Suggested repair procedures for water supply systems are listed below.

4.3.2.1.     Identify the Problem. The fi rst corrective action is to iden tify the extent of the problem. Pipes and mains, valves, and pumping stations can be located from existing utility drawings. If available, local technicians should be able to assist greatly in this effort. Multi-frequency pipe locators and similar equipment can be used to locate otherwise hidden lines.

4.3.2.2.     Select Repair Materials. Repairs can be accomplished with cast-iron pipe with mechani- cal couplings or by using ir on or steel pipe. Steel pipe is preferable to cast-iron pipe because it is stronger and lighter, can be fabricated in longer lengths, has fewer joints, and is easier to transport and handle. Fire hoses may also be used for temporary bypasses. Schedule 40 PVC piping can also be used as feeder lines. Plastic piping, which normally comes in 10-foot lengths, is very easy to assemble and modify. Mechanical couplers are generally desirable because they are quickly installed and resist vibr ation and settlement. The most common coupler s are the full circle and closed circle types. The full circle or open side couplers ( Figure 4.2.) are the most preferred and recommended for water, sewer, and POL line repairs. The closed ci rcle or closed side coupler is used primarily for steam line repairs. If normal repair materials, such as couplers, are not available to repair a broken pipe or leaking joint, other expedient line repair techniques are still available.

Figure 4.2. Typical Full Circle Couplers.

4.3.2.3.     Implement Repairs. Expedient repair to water distribution systems basically consists of piping. In essence, replace or repair piping syst ems with locally available materials or materials obtained by dismantling non-criti cal systems for components. Fi rst responders will nor mally attempt to isolate and/or bypass damaged lines. Once the damage has been assessed, make tempo- rary repairs to control water wastage, maintain essential flow, and permit the reopening of valves.

4.3.2.3.1.     Repairing Water Main Breaks and Leaks. Water main repairs should be repaired as quickly as possible. The type of repair technique that is used depends on the type of leak in the water main. Use the procedures in Table 4.1. as a guide for repairing water main breaks and leaks.

Table 4.1. Checklist for Repairing Water Main Breaks and Leaks.

4.3.2.3.2.     Tapping Water Mains. After a disaster or during a contingency, it may be necessary to tap into water mains to make expedient repairs or reroute essential service. Water mains are usually cast iron, 8 inches or more i n diameter. If the involved main is less than 8 inches in diameter, taps should be 2 inches or smaller. Use the steps in Table 4.2. and the illustration in Figure 4.3. to tap the water main.

Table 4.2. Steps to Tap a Water Main.

Figure 4.3. Water Main Tap.

4.3.2.3.3.     Making Temporary Repairs in Water Pipes. Although expedient repairs may not eliminate all leaks from water distribution pipes, small leaks should be repaired when the tac- tical situation or mission permits. Before making any repairs, shut off the water and relieve the pressure from the system. Pipes can be temporarily repaired using the following methods.

4.3.2.3.3.1.     Rubber Hose or Plastic Tubing. Cut the pipe on either side of the leak with a hacksaw or pipe cutter. Remove the damaged pipe section and replace it with a length of rubber hose or plastic tubing. To do this, slip the ends over the pipe and fasten them with hose clamps. The inside diameter of the hose must fit the outside diameter of the pipe.

4.3.2.3.3.2.     Sheet Rubber. Wrap the leaking area with sheet rubber . Place two sheet-metal clamps on the pipe (one on each side). Then, fasten the clamps with nuts and bolts.

4.3.2.3.3.3.     Electrician’s Friction Tape. Wrap several layers of friction tape around the hole or crack, extending the tape about 2 inches above and below the leak.

4.3.2.3.3.4.     Wood Plugs. Similar to water main repairs, small holes in other water pipes can also be filled with wood plugs. Drive a wooden plug into the hole after it is drilled or reamed. The plug will swell as it absorbs wat er, preventing it from being blown out by water pressure.

4.3.2.3.4.     Installing Temporary Piping or Hoses. These repa irs may involve plugging or cap- ping fractured mains or shunti ng water around breaks with a fire hose connected to the frac- tured pipe or fire hydrants. Ex pedient repairs could also consis t of new piping laid on the ground. Replace temporary piping and hoses with more permanent repairs as soon as possible because they may interfere with traffic, are likely to freeze in cold weather, and may not pro- vide sufficient supply. Figure 4.4. and Figure 4.5. give examples of typical service and water- line connections that may require repair.

Figure 4.4. Service Connections to Existing Mains.

Figure 4.5. Typical Waterline Connections.

4.3.2.3.5.     Repairing Burst Water Lines. Four examples of ways to repair a burst water line are shown in Figure 4.6.

Figure 4.6. Expedient Pipe Repair Techniques.

4.3.2.3.6.     Using Dissimilar Material s. During expedient repair, the goal is delivery. As such, the piping size must be based upon the sizes that the pumps will accommodate and the materi- als available. During contingency operations pr oper fittings, material, and tools may not be available. Therefore, the field eng ineer may have to improvise using dissimilar materials to effect temporary repairs. Figure 4.7. through Figure 4.9. illustrate a few ways to accomplish pipe repairs when working with limited resources or dissimilar materials. Regardless of what type of expedient repairs are performed, the total system will need to be disinfected when the repairs are completed.

Figure 4.7. Joining No-Hub Cast-Iron Pipe.

Figure 4.8. Working With Flexible Plastic Pipe.

Figure 4.9. Dissimilar Materials Jointing.

4.3.2.3.7.     Thawing Frozen Systems. Pipes may freeze in temperat e as well as frigid zones. In frigid climates, freezing presents a major problem to a water distribution system, and pipes are normally insulated and he ated. If a building’ s temperature falls below freezing, inside pipes may also freeze causing thepipe to break at the weakest point. The best way to avoid fro- zen pipes is to insulate or wrap lines with electrical heat tape. In areas where the ground is per- manently frozen, water pipes are placed in h eated conduits. Pipes are typically buried below frost penetration depth in temperate climates where freezing is only a seasonal problem. Even with proper protection, some pipes may still freeze. The paragraphs below discuss some pipe-thawing procedures.

4.3.2.3.7.1.     Electrical Thawing of Wrought-Iron and Cast-Iron Pipe. Electrical thaw- ing is quick and relatively inexpensive. Th e electrical circuit fo r the thawing operation consists of a sourc e of current (a DC genera tor, such as a welding unit, or a transformer connected to an AC outlet), a length of the frozen pipe, and two insulated wires connecting the current source and the pipe. As current fl ows through the pipe, heat is generated and the ice within the pipe begins to melt. As the water starts to flow, the rest of the ice is pro- gressively melted by contact with the flowin g water. The wires f rom the current source may be connected to nearby hydrants, valves, or exposed points at the ends of the frozen section. The amount of current and voltage required to thaw various sizes of wrought-iron and cast-iron pipe are given in Table 4.3. The time required for el ectrical thawing varies from 5 minutes to over 2 hour s, depending on the pipe size and leng th, the intensity of freezing, and several ot her factors. The best practice is to supply current until the water flows freely.

Table 4.3. Current and Voltage Required to Thaw Wrought-Iron and Cast-Iron Pipes.

4.3.2.3.7.1.1.     Precautions. In general, do not use a curr ent higher than the one listed in Table 4.3. for a particular pipe size. When in doubt, use a lower current for a longer period of time. Select contact points on the pipe as close as possible to the frozen sec- tion and make sure the contact points are free of rust, grea se, or scale. Remove any meters, electrical ground connections, and couplings to the building plumbing from the line to be thawed. If the pi pe joints have gaskets or ot her insulation, thaw the pipe in sections between the joints or use copper jumpers to pass the current around the insu- lated joints.

4.3.2.3.7.2.     Steam Thawing. Steam thawing is slower than electrical thawing and is used only when insulating ma terial in pipe joints or couplings makes the use of electricity impractical. In steam thawing, a hose connected to a boiler is inserted through a discon- nected fitting and gradually ad vanced as the steam melts th e ice. Steam thawing is com- monly used on fire hydrants.

4.3.2.3.7.3.     Thawing With a Heat Lamp or Blow Torch. A heat lamp or blowtorch is a good method for th awing aboveground pipes, but there is a risk of fire—especially with plastic pipes. Use the followi ng steps to thaw frozen pipe s when using a heat lamp or blowtorch: (1) open the faucets in the line; (2) apply heat from the heat lamp or blowtorch at one end of the pipe and work along the entire length of the pipe (Figure 4.10.); (3) con- tinue to heat the pipe unt il the water flows freely. Caution: Do not overheat the pipes, because soldered joints will break loose if the solder melts.

Figure 4.10. Thawing Frozen Interior Pipes.

4.3.2.3.7.4.     Thawing with Boiling Water and Thaw Pi pe. Follow the steps in Table 4.4.

and use the illustration in Figure 4.11. to thaw frozen exterior pipes.

4.3.2.3.7.5.     Other Thawing Methods. Pipes can also be thawed by wrapping them with burlap or other cloth and pouring boiling water over the wrappings, thus transmitting heat to the frozen pipe. In some cases, a small pump may be used to clear a piece of pipe. How- ever, excessive pump pressure can cause a backup; therefore, this procedure must be care- fully monitored. When indoor pi pes freeze due to failure in the heating plant, the heating plant must be repaired. A high temperature should be maintained in the building until the pipes thaw.

Table 4.4. Steps to Thaw Frozen Underground Pipes.

Figure4.11. Thawing Frozen Exterior Pipes.

4.4.     Water Treatment Systems. The expedient restoration of water trea tment capabilities may consist of repairs to an existing treatment plant or the installation of portable water treatment units. The importance of restoring the water tr eatment facility will depend upon the quality of the in stallation water source fol- lowing an emergency. If the source is relatively free of contaminants, treatment plant repairs or setting up of portable treatment equipment may be of less importance than othe r installation repairs. If water treatment is necessary and the treatment plant is beyond repair, or the installation does not possess a treatment facility, it may be necess ary to use expedi ent water treatment equipment. Th e most common expedient water treatment system available to civil e ngineer forces is the rever se osmosis water purification unit (ROWPU). The ROWPU purifies wate r by forcing water under high pre ssure through a series of mem- branes to eliminate impurities. The ROWPU is capable of removing disso lved minerals from water. Dis- infection treatment is accomplished only after processing through the membrane fi lter elements since chlorine causes acute damage to the filter elements. The producti on capability of the ROWPU will be reduced by high temperatures of the feedwater source. Although ROWPUs come in several sizes, the Air Force currently uses both the 600-GPH unit shown in Figure 4.12. and the 1500-GPH unit shown in Fig- ure 4.13. For more information on ROWPU operations, refer to AFH 10-222, Volume 9, Guide to Reverse Osmosis Water Purification Unit Installation and Operation.

Figure 4.12. 600-GPH Reverse Osmosis Water Purification Unit (ROWPU).

Figure 4.13. 1500-GPH Reverse Osmosis Water Purification Unit (ROWPU).

4.5.    Water Storage Systems. The water storage system on an air base or beddown location may consist of underground reservoirs, elevated water tanks, open reservoirs, and temporary storage facilities like those in Figure 4.14. The most severe damage to the storage system could be a rupture causing loss of the stored water. Another consideration is sabotage by clandestine groups. Whenever possible, water storage facilities should be postured well within the secure area of the installation or beddown setting. Ruptures or other damage to existing storage facilities can be sealed from the inside using rubber patches, epoxy, or wooden dowels if the holes are small.When conventional installation water storage facilities are damaged or additional storage space is required, swimming pools and similar watertight facilities make excellent alternate reservoirs. Other expedient water storage alternatives include: flexible bladders ranging in size up to a 50,000-gallon capacity, water distribution trucks, water trailers, lyster bags, 5- and 10-gallon igloo water coolers, and 55-gallon drum s. An aboveground reservoir can be constructed using sandba gs or earthen berms lined with plastic sh eeting to make it watertight. Bear in mind that a considerable amount of water is stored within the pipelines themselves. For example, a 6-inch pipeline, two miles long contains approximately 16,000 gallons when full. Using shutof f valves to quickly isolate undamaged sections of the distribution system could mean substantial amounts of water saved within the pipes for future use.

Figure 4.14. Temporary Water Storage Facilities.

4.6.    Expedient Water Sources. The source of water for an air base or beddown location may be as var- ied as a commercial supplier, a ground water source, or a surface water source (Figure 4.15.). Damage to a commercial water supply during an emergency will normally consist of a ruptur ed or blocked supply line that results in either reduc ing or eliminating the base water supply. Ground water sources, water pumped from below the surface, are probably the least vulnerable supply sources. It can be assumed most natural disasters or hostile attacks would not destroy this type of wa ter source. However, some emergen- cies can cause damage to the well and pumping systems that give access to this source. Specifically, wells could be partially filled with debris, well walls and pumping facilities damaged or destroyed entirely. Var- ious types of emergency situations can af fect surface water sources a lso. Water-borne debris associated with a flood or hurricane might block water inlets to the system; nuclear, biological, or chemical contam- inants used during an en emy attack could make the source unus able; or conventional enemy munitions may diminish, divert, or stop access to a river or lake. Other sources of water available to the civil engi- neer force are sometim es overlooked. In cold weather regi ons there are vast amounts of “solid” water available in the form of snow and ice. Snow and ice melting devices can be fabricated and used to provide excellent water supplies from glaciers and other ice formations. Base swimming pools, ornamental pools, and similar facilities often contain substantial amounts of water, which can be used during emergencies. Table 4.5. through Table 4.8. show the characteristic advantages and disadvantages associated with sup- plying and using water in the four major climatic regions of the world.

Figure 4.15. Sourcing Water for Earthquake Victims (Turkey 1999).

Table4.5.TemperateRegions.

Table4.6.TropicalRegions.

Table4.7. Frigid Regions.

Table 4.8. Desert Regions.

4.6.1.    Water Sources Development. Once water sources have been identified for a beddown loca- tion, the field engineer must further develop and maintain these sources for use. General tasks involved in this process include, (1) developing water points by creati ng ponds and lakes across streams, deepening and reinforcing existing water collection areas; (2 ) providing drainage to prevent contamination of water sources from storm runoff; (3) constructing physical protection structures for water sources; (4) constructing and improving roads from water points and well sites to the main sup- ply routes; (5) maintainin g, repairing and buildin g semi-permanent and pe rmanent water utilities at existing installations; and (6) repairing and constructing water storage and distribution systems.

4.6.2.    Surface Water Resources. Surface water from ri vers, streams, lakes, or spri ngs is the most common sources of water supply . Surface water sources must be tr eated according to established water treatment procedures and standards to ensure water is potable before use. Refer to AFH 10-222, Volume 9 for water treatment procedures. The capacity of small streams to meet supply requirements may be increased by the construction of small dams or reservoirs. Expedient structures for this pur- pose are shown in Figure 4.16. through Figure 4.18. In regions such as tropical islands where there is abundant rainfall and rapid surface runof f, rainwater is the primary source for the inhabitants, how- ever, the quantity of water available may not be sufficient to supply the needs of both the civilian pop- ulation and the military. Rainwater as a source may be sufficient for small units for limited operations, but it should not be considered if other more reliable sources are available.

Figure 4.16. Expedient Dam and Reservoir Layout.

Figure 4.17. Typical Small Expedient Dam.

Figure 4.18. Improvised Dam for Impounding a Small Stream.

4.6.3.    Water Intakes. Once the natural water resources are confined in a reservoir the water must be delivered to the point of usage. This is generally accomplished by pumps or gravity pipelines. Intakes are used as a means of obtaining water from its source. Water at the intake point should be as clear and deep as possible. Screens are installed on all in takes regardless of how clean the water appears. Screens used at surface sources serve to keep fish and debris out of the water system. Special attention must be given to the intake. If a lot of muck or silt is on the bottom of the water source, a floating type intake is best. On the other hand, if bottom of the water source is a bed of sand or gravel, a surface intake with a screen may be equally effective and easier to use.

4.6.3.1.     Floatable Intakes. Floats made of logs, lumber, sealed cans, or empty fuel drums can be used to support the intake strainer in deep water. They are especially useful in large streams where the quality of the water varies across its width or where the water is not deep enough near the banks to cover the intake strainer. An adequate depth of water can cover t he intake point by anchoring or stationing the float at the deep part of the stream. The intake hose should be secured to the top of the float, allowi ng enough slack for movement of the float. If support lines are used to secure the float to the banks, the position of the float can be altered to correspond to changes in depth by manipulation of the lines. The chief advantage of a float intake is the ease with which the screen can be adj usted. Figure 4.19. and Figure 4.20. illustrate two type s of improvised intake floats. Note: The strainer on the suction hose of a floating intake should be placed at least 4 inches below the water level. This precaution reduces the possibility of the strainer becoming clogged with floating debris, or the loss of prime owing to air entering the suction line.

Figure 4.19. Drum Float Type Water Intake.

Figure 4.20. Log Float Type Water Intake.

4.6.3.2.     Rock and S take Supported Intakes: If the stream is not too sw ift and the water is deep enough, an expedient intake may be prepared by placing the intake strainer on a rock. This will prevent clogging of the strainer by the streambed and provide enough water overhead to prevent the suction of air into the intake pipe. If the water source is a sm all stream or shallow lake the intake pipe can be secured to a post or pile as shown in Figure 4.21.

Figure 4.21. Stake Supported Water Intake.

4.6.3.3.     Pit Supported Intakes. When a stream is so shallow thatthe intake screen is not covered by at least 4 inches of water , a pit should be dug and the screen laid on a rock or board placed at the bottom of the pit. Pits dug in streams with clay or silt bottoms should be lined with gravel to prevent dirt from entering the purification equipment (Figure 4.22.). The screen is surrounded by gravel that prevents collapse of the sides of th e pit and shields the screen from damage by lar ge floating objects. The gravel also acts as a coarse strainer for the water. Enclosing the intake screen in a bucket or other container as shown in Figure 4.23. may provide a similar method.

Figure 4.22. Typical Gravel Pit Intake.

Figure 4.23. Bucket Use with Gravel Pit Intake.

4.7.    Wastewater (Sewage) Systems. Improper disposal of sewage in the aftermath of a disaster or enemy attack will compound base recovery problems. If the sewage enters a water supply, an outbreak of intestinal diseases such as typhoid, cholera, dysentery, and diarrhea, is almost certain to occur. To prevent such outbreaks, civil engineer forces may have to repair damage to existing sewer systems as well as pro- vide temporary sanitation facilities. The priority of these repairs will be based on an estimate of potential hazard to the installation population.

4.7.1.    Classification of Air Base Sewage. Sewage may be divided into several classifications accord- ing to its source. These classifica tions will decide the imm ediate need for sewe r rehabilitation. The two primary types of sewage on most installations are domestic sewage and storm sewage.

4.7.1.2.     Storm Sewage. Storm sewage is the inflow of surface runoff during or immediately fol- lowing a storm or heavy rain. Disposal of storm sewage following a disaster is not a high priority unless it hinders base operations or endangers lives by flooding critical areas. Since storm sewers are designed to catch runof f whether it is natural or man-made, th ey will also ca tch and collect toxic chemicals introduced accide ntally or on purpose. For this reason, civil engineers should be prepared to establish blocking points at critical locations to prevent the spread of hazardous mate- rials. Storm sewers may be blocked using commercially available plugs or sandbags.

4.7.2.    Sewage System Operation. Themajor components of the sewage system consist of facilities for collecting, pumping, treating, and disposing of sewa ge. The basic collecting system consists of a series of branch, lateral, main, and trunk sewers leading from various installation structures. Raw sew- age moves through the collection system to a central point for treatment and eventual disposal. At any point along the system where gravity is not sufficient to move the sewage, a pump or lift station may be required. Sewage treatment plants vary in complexity according to the characteristics of the influ- ent and the degree of treatment requ ired prior to discha rge. Effluent standards, set by national and local regulations, determine the degree of treatment.

4.7.3.    Anticipated Sewer Damage. Common problems with the sewage system during typical disas- ters such as floods and hurricane s are complete inundation of th e system by excessive amounts of water and blockage of parts of the system by debris. In the extreme, earthquakes or enemy attacks can cause complete destruction of treatm ent plants and lift stat ions as well as rupt ures of sewage lines. Damage sustained during hostile attacks will probably be collateral in nature since the sewage system is not normally a preplanned target. Specific damage could consist of the following:

4.7.3.1.     Sewers. Deliberate demolition to sewers by an enemy is usually limited to junction man- holes or large mains. Stoppages caused by debris being blown and washed into sewers can be expected.

4.7.3.2.      Pumping S tations. During conflict, pum ping stations may be deliberately damaged because they are key points, are more accessible, and are most dif ficult to repair. They are not likely to be damaged seriously by bombs or artillery fire since they offer a relatively small target. However, flooding during either tropical storms or tornados can prove consequential.

4.7.3.3.     Treatment Units. Treatment units may be damaged during a conflict by the demolition of machinery and other key equipment. However, they are not norma lly high-value targets due to their small size and the ability to achieve effective treatment results by other means.

4.7.3.4.     Cesspools and Sep tic Tanks. Damage to cesspools an d septic tanks from sabotage or bombing is relatively unimportant. Destruction of a cesspool or septic tank would affect only one or a small number of properties. Their wide dispersal provides a large measure of safety.

4.7.4.    Effect of Damage. Human wastes must be properly disposed of in order to protect personnel. If sewage enters a water supply , an epidemic outbreak of intestinal diseases such as typhoid, cholera, dysentery, and diarrhea is almost certain to follow . Existing sewer systems ma y have to be rehabili- tated to prevent such mission-impacting outbreaks.

4.7.5.1.     Sewers. Sewer lines are the most essential item in a sewage disposal system. If the situa- tion is critical, service can be restored temporarily by pumping from an upstream manhole, around the damaged section, and into a downstream manhole. If the sewer is completely stopped or badly damaged, an open channel can be built. Where storm and sanitary sewers are separate, it may be possible to divert sanitary sewage through a storm sewer to a suitable outlet.

4.7.5.2.     Pumping Stations. When sewage pumping stations cannot be repaired expeditiously using available replacement parts or parts cannibalized from other st ations, portable pumps should be substituted. If pumps are not availabl e, consider rerouting past the lift station with pipe or open channels using gravity flow.

4.7.5.3.     Treatment Plants. It may be necessary to bypass severely damaged treatment plants. Set- tling and digestion tanks and filters can usually be repair ed with standard construction materials. Sludge beds are practically indestructible. M achinery must be repair ed by cannibalization or improvised methods. If compressed air is used in an activated sl udge process, replacement of air compressors is difficult at best. However, the activated sludge plants can be operated as sedimen- tation or septic tanks. Such treatment, together with chlorination, provides a reasonable degree of purification. Further information about expedient septic systems is provided in Chapter 6 of this pamphlet.

4.7.5.4.     Septic Tanks. Septic tank systems ( Figure 4.24.) are used to treat and dispose of waste- water from buildings wher e it is not feasible to provide a community wastewater collection and treatment system. A septic tank speeds up the decay of raw sewa ge. It may be made of concrete, stone, fiberglass, or brick (lumber is used when other materi als are not available), in box-section form, and it should be watertight. The septic tank should have a manhole and cover to give access for cleaning and repair and must be designed to hold 70 percent of the peak water demand of that facility for 24 hours and not less th an 16 hours. Contingency rapid re pair of a septic tank would normally be low prio rity since other options ar e usually available. However, if a septic tank is severely damaged and totally inoperable and othe r prudent options are not available, an expedi- ent-type septic tank can be constructed using procedures provided in Chapter 6 of this pamphlet. Otherwise, expedient repairs w ould probably be limited to unc logging pipes, pumping out tanks, and improving or expanding drain fields.

Figure 4.24. Typical Septic Tank.

4.7.5.5.     Grease Traps. Grease traps come in countless sh apes and sizes, but their operation is basically the same. Just as the name suggests, a grease trap catc hes grease (animal fats and oils) from kitchen wastewater. Although there are ma ny different models, grease traps are typically placed in the flow line of the building’s sewer system to ca tch grease and fats from kitchen and scullery sinks, preventing clogs in the waste pipes. Expedient repair of grease traps is usually lim- ited to unclogging inlet pipes and repairing or replacing damaged traps. Service personnel should be trained to perform routine cl eaning and maintenance of grease traps installed in their area(s) . Figure 4.25. provides a layout of a typical grease trap.

Figure 4.25. Typical Grease Trap Layout.

4.7.5.6.      Additional details on water supply and wastewater sy stems repair procedures can be obtained in the following documents:

4.7.5.6.1.     Water Systems: UFC 3-230-02, Operation and Maintenance: Water Supply Sys- tems, and MIL-HDBK 1005/7A, Water Supply Systems.

4.7.5.6.2.     Wastewater Systems: UFC 3-240-07FA, Sanitary and Industrial Wastewater Col- lection: Gravity Sewers and Appurtenances; UFC 3-240-08FA, Sanitary and Industrial Waste- water Collection: Pumping Stations and Force Mains; and MIL-HDBK 1005/16, Wastewater Treatment System Design Augmenting Handbook

4.8.    Natural Gas Systems. Damage to a natural gas system must be dealt with rapi dly to prevent and contain potential accidents like the one shown in Figure 4.26. The most expedient method of dealing with gas system leaks is to shut off the gas supply at main feeder po ints. Since gas is often not essential to installation operations, selective syst em isolation can usually be used until time and resources are avail- able to make the necessary permanent repairs.

Figure 4.26. Ruptured Natural Gas Line Fire.

4.8.1.    Emergency Cut-Off Procedures. If it is not possible to shut the gas off through the use of exist- ing valves, gas main bags or gas stoppers, as shown in Figure 4.27., may be required. Gas main bags are canvas or rubber bags which can beinserted into a gas main and inflated until they fill the pipe and halt the gas flow. The gas stopper consists of oiled or rubber -coated canvas stretched over a flexible steel frame. The edge of the stopper forms a seal with the interior of the gas main thereby stopping the gas flow. To seal a main with a gas bag, the rubber or canvas bag isinserted through a hole in the main (a hole created by damage, removal of a riser, or access port). If the interior of the pipe is coated with tar or oil, canvas bags are necessa ry. The bag is then inflated through a piece of attached tubing until it fills the pipe and stops the gas flow. To use a gas stopper, the frame is squeezed together and inserted into the hole in the gas main. After the stopper is in the pipe, it is restored to its circular shape through the use of wire levers attached to the frame. The ga s stopper can then be adjusted to shut of f the gas flow. In larger mains, it is safer to use both bag and stopper.

Figure 4.27. Typical Gas Main Bag Kit.

4.8.2.    Expedient Repairs of Gas Systems. As mentioned earlier, it is best to simply cut off gas systems and make permanent repairs later when the emergency has subsided. However, certain conditions may call for some immediate expedient repairs to prevent danger to personnel or to provide limited gas ser- vice.

4.8.2.1.     Venting of Gas Accumulations. After the main gas supply is shut off, immediately check buildings and other areas for th e presence of dangerous gas accu mulations. The presence of gas can be detected through the use of special gas detection devices such as a combustible gas indica- tor or, when no detection instrument is availabl e, by an individual’s sense of smell. The sense of smell cannot always be depended on to detect leaks because ga s can lose its odor while traveling through the ground. Any accumulations should be vented to the outside to reduce the potential for asphyxiation or explosion.

4.8.2.2.     Repair of Broken or Punc tured Gas Pipes. There may be conditions following an emer- gency when gas must be supplied to certain facilities for esse ntial operations. For example, the dining hall may have no alternate method of preparing food for the recovery force, or the hospital may need hot water for crucial medical services and have no other source of energy for water heat- ers. During periods of cold weather, gas may be the only source ofheat for certain mission-critical installation facilities. Under any of these conditions, leaking or ruptured gas lines may require patching. If the leak is small a nd involves low-pressure gas pipes, a sealant may be used in con- junction with a pressure mold to close the opening. The sealant should be a product which does not break down in the presence of natural gas. Larger leaks and pipe breaks can be repaired using various types of mechanical clamps.

4.8.2.3.      Safety. The potential for asphyxiation or explosion during encounters with gas leaks makes it imperative that the repair crew exercise extreme caution. Personnel should not enter con- fined areas with high gas accumu lations unless they are equipped with self-contained breathing apparatus. No open flame from cutting torches, ci garette lighters, or similar devices will be used in a gaseous environment. Additiona lly, the repair crew must be careful not to generate sparks in the vicinity of a gas leak. A good rule of thumb is not to enter any area where the mixture of air and gas is at, or approaches, the lower explosive limits. Taking a few extra minutes to properly vent the area will greatly reduce the danger to personnel.

Figure 4.28. Common Gas Leak Detection Devices.

4.9.    POL Systems. An installation’s petroleum, oils and lubricants (POL) system is a key utility that has two primary components: storage facilities and distribution systems.

4.9.1.    Storage Facilities. Most installations have several days of storage capacity for major fuel prod- ucts. POL storage methods vary considerably from installation to installation. At some CONUS installations, there are large fixed storage tanks located aboveground (Figure 4.29.). Conversely, POL storage tanks at most overseas locations are both dispersed and covere d by a protective layer of soil. In both instances, engineer forces will only be able to accomplish expedient repairs if the involved damage is superficial.

Figure 4.29. Altus AFB POL Tank Farm.

4.9.2.    Distribution System. The POL distribution consists of pum ping stations, pipelines, and dis- pensing points. The nature of construction of the POL distribu tion system makes it relatively safe from natural disasters othe r than flooding. The ma jor damage that a POL distribution system might receive would more likely result from an enemy attack during wartime. The impact of damage will be reduced at installations where the distribution system is interconnected. As a protective measure, most control valves at a number of overseas locations have been installed inpits in order to limit their expo- sure to direct impact during an attack.

4.9.2.1.     Pumping Stations. POL pumping stations are not easy targets to hit, however, and would not be considered primary tar gets during an en emy attack. Some loss es to pumping capability should be expected from collateral damage but it is likely that some capacity to pump fuel will be retained.

4.9.2.2.     Pipelines. POL pipe lines are essentially al l welded steel. They are the most survivable POL system component. However, since the distribution system piping is the most extensive ele- ment of the POL system, it is the most likely element to be damaged. The impact of such damage will be reduced at installations where the distribution system is looped.

4.9.2.3.     Dispensing Points. Dispensing points range fr om vehicle fill stands to concrete-encased aircraft hydrant refueling systems. The fill stands service POL tank trucks for refueling aircraft at most locations. Damage to fill stands can be expected as a collateral effect of weapons detonation. Hydrant refueling systems, however, because of their “hardness,” should remain relatively intact.

4.9.3.    POL Repair Actions. Damage to the POL system is compounded by the volatile nature of the system contents. Engineers will ha ve to think in terms of expedien t repairs to water systems and use whatever spare parts and materials currently exist in bench stock or special levels. However, unlike water systems, POL repair crews will have to be especially concerned with toxicity, flammability, and compatibility issues. Primarily for Pacific theater installations, the POL rapid utility repair kit (RURK) provides a means of quickly repairing valve and line failur es resulting from an attack or disaster. For additional information on the POL Utility Repair Kit or the Contingency Fuel Recovery System, refer to the associated Qualification Training Package (Figure 4.30.).

Figure 4.30. POL Qualification Training Packages.

Chapter 5

EXPEDIENT REPAIR OF HVAC AND ELECTRIC SYSTEMS

5.1.    Introduction.Air bases need viable power source to support mission operations. Electrical power is essential to daily activities; and, to a lesser de gree, Heating, Ventilation, and Air Conditioning (HVAC) systems are also necessary. Obviously, having effective heating and air conditioning for personal comfort has a minimum impact on aircraft sortie generation. However, in today’s operating environment, a large number of mission-critical systems and electronic equipment require stringent climate control. For exam- ple, many command and control cente rs are self-contained operations that cannot function without inde- pendent electrical or HVAC support. In these situations, adequate HVAC systems are critical to mission accomplishment.

5.2.    Overview. This chapter focuses on expedient HVAC and electrical repair options during contin- gency situations. Specific topics include recovery concepts and expedient repair of heating, air condition- ing, and electrical distribution systems. Each of these areas deals with ha zardous materials and may require work on or near ener gized circuits; therefore, only trained technicians are allowed to accomplish HVAC and electrical system repairs and modifications, while strictly complying with Air Force electrical safety criteria. Electrical safety requirements in AFI 32-1064 , Electrical Safe Practices, and UFC 3-560-01, Electrical Safety O&M, are mandatory and outline the type of arc thermal performance value (ATVP) rated PPE to wear when wo rking on or near energized circuits, when work on or near ener gized circuits is authorized, and who is the energized work authority. Table 4-2 in UFC 3-560-0 defines hazard./ risk category classifications for work tasks. In addition, due to the complexity of these systems, the scope of this document is to pr ovide only basic expe dient repair guidelines for use during emergencies. Addi- tional information is provided in the references listed in Attachment 1.

5.3.    Heating Systems. In general, heating systems carry heat from the point of production to the place of use, and their design can be complex with many variations. They are usuall y classified by the medium used to carry the heat fromthe source to the point of use, such as hot water, steam, and forced-air systems.

5.3.1.    Heating Systems Repair. Depending upon weather c onditions at the time of a disaster or attack, repairing damage to the h eating system can range in importan ce from critical to insignificant. The extent of damage can span the gamut from nothing whatsoever to total destruction. However, unless the installation is undergoing a period of severe cold, repairs to heating systems servicing non-mission-essential facilities can probably be delayed throug h the use of spa ce heaters and the wearing of additional clothing. Ho wever, if repairs must be made , concentrate on minimum efforts necessary to return some measure of heat to base facilitie s. It is not necessary to attain pre-disaster comfort levels following an emergency. A partial return of heat can raise temperatures to a level that will allow normal operations if personnel are warmly clothed.

5.3.1.1.    Central Heating Systems Repair. For those installations that have a lar ge central heat- ing system, damage following an attack or disaster can be widespread. It may well involve the pro- duction plant along with the distribution system. The feasibility of conducting expedient repairs to the heating system will depend to a great degree upon the amount of damage incurred. For exam- ple, if an earthquake or bomb explosion causes a la rge rupture of the central boiler, it is unlikely that expedient repair techniques will suffice. On the other hand, a break in one of the pipes leading from the boiler could probably be expediently repaired. Fortunately, the inherent strength of materials used to contain the pressure within the system also serves to protect the system from external damage. Expedient repairs to central heating systems may consist of the following:

5.3.1.1.1.     Production Plant Repairs. Expedient repair of heat production plants may be delayed pending structural and/or electrical support. Damaged walls may have to be shored to prevent structural collapse or electrical utility service may have to be restored to power control and monitoring devices. From a mechanical perspective, broken pipes may need to be repaired or replaced, damaged automatic controls may have to be bypassed with manual ones, and internal cannibalization may be require d in order to get some boilers back in operation. As stated earlier, however, if a plant’ s boilers have sustained signifi cant damage, the production plant is probably beyond immediate repair.

5.3.1.1.2.     Distribution System Repairs. The high heat and pressure associated with most heating systems are characteristics that preclude the use of many expedient repair methods and materials used to otherwise correct water distribution system damage. For example, temporary connectors, such as fire hoses, which are ef fective in bridging damage to a water distribution system, will likely not tolerate the high temperatures and pressu res of a heat distribution line. Similarly, a standard sealer or joint compound which could patch a water leak will break down when applied to a steam line. If repairs are attempted, only materials which have been specifi- cally designed to withstand th e stresses imposed by heating systems s hould be used. Pipe replacement and welding are the most common re pair techniques used to correct distribution system problems. Caution must be exercised, however, since welding of high-pressure vessels is a specialized technique and requires substa ntial experience. You cannot slap together a steam line, even in a contingency mode, and e xpect it to work. In overseas areas, expect to encounter older systems which may contain components that are no longer in production. Repair parts for these facilities may have to be custom fabricated or cannibalized from other systems. Most locations, however, should have an emergency stock of heating system materi- als. Tap this source as much as possible.

5.3.1.2.    Individual Systems Repair. Installations without a central heating system generally fea- ture individual building systems. The great advantages of these independent units are that damage is limited to the system which supports a single building and genera l repair concepts are, for the most part, universally applicable. The basic question then becomes whether or not to repair.

5.3.1.2.1.     The easiest way to deal with a damaged individual heating system is to ignore it. If the weather permits, or the facility is not critical to the base mission, delay repairs until emer- gency conditions are essentially over. Another quick alternativ e when extensive repairs are required is to move personnel into a nearby building with a working heating system.

5.3.1.2.2.      Expedient repairs to an individu al heating unit are gene rally less complex than repairs on a large central system. Damage is confined and easy to determine since the indepen- dent system does not involve a dispersed ne twork. Components are sma ller, making it easier for repair crew members to install replacements. Also, spare parts may be more readily avail- able from base supply and local vendors. Furt hermore, since there often are many facilities containing similar individual heating systems, there are more opportunities for cannibalization of parts from low- priority buildings. If the damage is limited to the system’s ducting, tempo- rary flexible ducts can be rapidly put in place to correct the problem. Figure 5.1. shows exam- ples of flexible ducting.

Figure 5.1. Typical Flexible HVAC Ducting.

5.3.2.     Alternative Heating Source s. If attempts to re pair existing installation heating systems fail, temporary heating sources can be provided for mission-essential facilities. Remember, however, alter- nate heat sources can be dangerous and require fre quent checks and servici ng. As time permits, sys- tems should be repaired by using existing stocks or canni balized materials, thereby freeing the portable heaters for use elsewhere.

5.3.2.1.    Space Heaters. Various types of space heaters provide an alternative to central or indi- vidual heating systems. Fuel-fired heaters (Figure 5.2.) can be used in large open buildings if the odor is not objectionable and explosive vapors are not present. The propane heater on the right of the figure delivers 8,000 to 24,000 BTUs of portable, infrared heat from a common 20-lb propane cylinder. A number of variations are readily available o n the open market, including lar ger units designed to meet higher heating demands. Table 5.1. provides approximate propane fuel con- sumption information for various temperatures. In general, open flame heaters are dangerous, especially the unvented type. If they are used th e catalytic types are the safest. Electric heaters (Figure 5.3.) provide a safe alternative to open flame units provided temporary wiring and power sources can handle the extra load. Space heaters can be obtained from various sources. BEAR assets contain units ( Figure 5.4.) that can be used in permanent structures or tents. Commercial space heaters may be available from local vendors. Some installation units may also have portable shop heaters which can be reassigned to more critical facilities.

Figure 5.2. Typical Portable Fuel-Fired and Propane Heaters.

Table5.1.PropaneVaporization Rate Information.

Figure 5.3. Typical Industrial Portable Electric Heater.

Figure 5.4. BEAR Heater Asset.

5.3.2.2.    Cart-Type Ducted Heaters. Cart-type ducted heaters provide an excellent alternate heat source because combustion stays outside the structure being heated . The units may be ava ilable from organizations on base , such as aerospace ground equi pment (AGE) or communications squadrons, after requirements for aircraft sorties and other vital operations have been met.

5.3.2.3.    Improvised Heaters. The use of improvised heaters should be avoided except in cases of extreme cold and where no other alternative exists. The primary dangers inherent with improvised heating systems are the possibility for asphyxiation and fire hazard potential. Caution must be taken to ensure that dangerous fumes are vented during combus tion and any open flame is prop- erly contained. One of the most common types of improvised heaters consists of a 55-gallon drum converted for use as a burner coupled with makeshift sheet metal ducting to vent fumes to the out- side. Remember, improvised heaters do not completely contain combustion vapors. Therefore, even with vents to the outside, makeshift heaters should never be used in totally enclosed areas.

5.4.     Air Conditioning Systems. Most, if not all, installations have some facilities that ca nnot function properly without air conditioning a nd/or climate control support. T oday’s Air Force relies on sophisti- cated electronics that supp ort the operation and maintenance of such things as aircraft navigation and attack systems, computer systems, communications, and air traffic control equipment. These systems are highly susceptible to heat build-up and fail rapidly if subjected to overheating conditions. This situation makes air conditioning support critical to these mission-e ssential facilities. As a general rule, air condi- tioning systems are more vulnerable than their heating counterparts. Most critical climate control system components are located externally to the facility they serve and therefore are more susceptible to damage. Two air conditioning or r efrigeration systems are used by the Air Force: the vapor compression system and the absorption system. The vapor compression system is the most common.

5.4.1.     Repair of Air C onditioning Systems. Typical air conditioning repairs tend to be manpower intensive and usually take a considerable amount of time. Like heating systems, air conditioning sup- port is highly dependent on a reliable electric supply. In addition to being time intensive, it is common to have a very large number of unit and system va riations present on the average base. These factors make developing an expedient repair strategy and standardized repair kit to satisfy all potential needs both cost prohibitive and virtually impossible. Expedient repairs may typically involve replacing parts and locating and repairing leaks within the system.

5.4.1.1.    Replacing Parts. If system rejuvenation is pl ausible and parts are not available in a stan- dardized repair kit, consider obtaining needed parts from similar units that support less critical functions.

5.4.1.2.    Leak Testing and Repair. If a mission-essential refrigeration unit is operable except for minor leaks after a natural disaster or damage from attack, the usual first course of action would be to charge the unit as a temporary measure and move on to the next issue. However, if the situation allows for a more concerted effort, permanent repairs should always be considered to avoid dupli- cation of effort. When a leak is found and repaired, the complete unit should be rechecked not only to confirm the repair, but also to ensure that there are no additional leaks.

5.4.1.2.1.     The method for leak testi ng varies with the refrigeran t used. However, most meth- ods involve applying pressure to the system with an inert gas, such as nitrogen or carbon diox- ide. With proper care, nitrogen or carbon dioxide may be used safely when pressure-testing for leaks. However, be aware that the pressure in a nitrogen cylinder is us ually about 2,000-psi and the pressure in a carbon dioxide cylinder is normally about 800-psi. Consequently, a pres- sure-reducing device that has both a pressure regulator and reli ef valve must always be used when testing with either of these gases. Check the system’s nameplate before conducting this type of test. In most cases, it will provide recommended testing pressures. If this information is not provided, UUnever UU test all or part of a hermetic sy stem at pressures exceeding 170-psi.

5.4.1.3.    Leak Detection Devices. As a general rule , refrigeration system leaks are usually very tiny and require sensitive dete cting devices. Commonly used detection devices include bubble solutions, fluorescent dye, and electronic detection devices such as the corona discharge (Figure 5.5.), heated diode (Figure 5.6.), and UV lamps. The newer electronic detectors can be used with R-134a, R-123, and other new alternative refrigerants.

Figure 5.5. Corona Tester.

Figure5.6. Heated Diode Tester.

5.4.2.     Alternative Air Conditioning Sources. If ai r conditioning systems cannot be expediently repaired after an attack or natu ral disaster, portable units are the ideal w ay to go u ntil time and resources allow permanent repairs. A number of BTU vari ations are available that support air condi- tioning requirements, ranging from sm all area units to lar ge package configurations used for cooling entire buildings. Two examples of large portable units are shown in Figure 5.7.

Figure 5.7. Typical Large Portable Air Conditioning Units.

5.5.      Electrical System. After an attack or disast er, power for airfield lighting, navigational aids (NAVAIDS), communications centers, C2 nodes, medical facilities, and other important activities must be restored before the installation can resume its operational mission. If the attack or disaster resulted in downed or damaged electrical lines, the repair or isolation of life-threatening electrical hazards must also receive high priority.

5.5.2.    Primary and Secondary Circuits. The electrical system can be divided into two major sub- systems: primary circuits and secondary circuits. Circuits above 600 volts are generally referred to as primary or feeder circuits. Circuits carrying less than 600 volts are usually referred to as low voltage or secondary circuits. Even in a contingency situation, work on the high-voltage primary systems will be performed only by craftsmen with specialized qualifications and equipment.

5.5.3.    Components of Electrical System. The electrical system supporting a typical installation consists of three components: pr oduction, distribution, and interior wiring. Each component of the system should be viewed in term s of its anticipated da mage during a continge ncy and the expedient repair techniques needed to adequately remedy the damage.

5.5.3.1.    Production Systems. At overseas installatio ns, electrical power is either supplied by base power plants or commercial sources. In the CONUS, primary power is most likely provided by a commercial grid. If the commercial source is interrupted, usually the only alternative is to dis- connect the impaired po wer source from the dist ribution system and su bstitute generators to power vital facilities. Most mission-essential facilities already have dedicated standby generators with an automatic transfer capability to maintain operations in the event the prime power is lost.

5.5.3.2.    Distribution Systems. The power distribution system may consist of substations, switchgear, and utility lines that are either overhead or underground. Overhead power lines and the associated utility poles are likely to suffer extensive damage during a hurricane, tornado, or enemy attack. An underground system, although better protected from th e high winds common to hurri- canes and tornadoes, is still vul nerable to the effects of an earthquake, flooding, or enemy muni- tions. There are three basic ty pes of distribution systems: radial, loop, and network. Any combination of these three systems can be found at most installations.

5.5.3.2.1.     Radial System. The radi al layout is one in which a mainline is established through the approximate center of an installation and branch lines are run from the main to power var- ious facilities. A very basic radial layout is shown in Figure 5.8. The primary disadvantage of the radial layout is that a break of wires at point “B” results in a complete loss of power to all facilities on the installation. Thus, the radial system is less effective since it is very susceptible to extreme weather conditions, war damage, a nd sabotage. However, since the radial system requires considerably less material, manpower, and time to construct, radial systems are often used during contingency beddowns.

5.5.3.2.2.     Loop System. A loop or ring layout supplies power to a facility from more than one direction as shown in Figure 5.9. Note that a break in the circ uit at point “A” will not cause complete power failure since power may still be distributed through the lower section of the loop. Thus, a loop system has an inherent capabi lity to prevent complete power loss of all facilities. Faults in the circuit can be isolated and repaired without large disruption of service. In addition, the loop layout normally distributes power with less voltage drop. The primary disadvantage of the loop system is that it requires more material and time to construct than the radial system.

Figure 5.8. Basic Radial Layout.

Figure 5.9. Basic Loop Layout.

5.5.3.2.3.     Network System. A network system is simply a merger of both the radial and loop systems. In particular, it uses the independent feeder system of the radi al system to supply power to distribution tran sformers while also paralleling th e secondary lines that are used in the loop concept. This c onfiguration capitalizes on the strong individual points of both the radial and loop systems, thereby allowing optimum flexibility and efficiency.

5.5.3.3.    Interior Wiring. After transmission and distribution systems, the “third leg” of the elec- trical system is the inte rior wiring. It generally consists of the electrical wiring, switches, outlets, circuit breakers, and other electrical accessories located within a building after the service entrance interface.

5.5.4.    Repairing Electrical Systems. After assessing the initial damage to an electrical system after an attack or disaster, the first action should be the isolation of those damaged areas presenting life-threatening hazards to personnel or posing the potential for additional property damage. Once ini- tial isolation is accomplished, damage control center (DCC) personnel, using installation utility plans and maps, determine how to best restore electrical power to vital installation facilities. Typically, this is accomplished by rerouting po wer lines to bypass damaged area s. After damage assessment data have been posted to the installati on utility maps, the DCC should be able to quickly direct electrical system rerouting using the existing, undamaged circuits. When rerouting around damaged areas, remember that non-standard materials can be used provided they do not jeopardize safety. If capable of carrying the required loads, wires and cables of different sizes or those normally designed for other uses may be substituted as expedient power lines. Strictly adhere to electrical safety requirements out- lined in previous paragraphs and ensure proper “phasing” of cond uctors is accomplished. Addition- ally, conductors, wire, and other components may be salvaged from unimportant or abandoned facilities.

5.5.4.1.    Repairing Power Production System. The extent of damage to an independent power pro- duction plant on the installation will vary with th e type of emer gency that has occurred. Natural disasters, such as hurric anes and tornadoes, are likely to cause st ructural damage to the plant as well as disrupt the plant’ s connections to the distribution system . An enemy attack will probably cause structural damage and disruption of connections to the distribution system, and it may pro- duce damage to other components of the power system; e.g., demolished control equipment, bro- ken turbine blades, and shattered insulators and bushings. In re pairing such damage, take full advantage of bench stocks maintained by each power plant or draw on ba se supply sources. As a last resort, try cannibalization. Generators, as an alternate power source, will probably be in short supply, making it imperative that these vital assets be properly positioned and maintained. Gener- ators should be limite d to providing power to only those faci lities that are absolutely crucial to base operations. AFI 32-1063, Electric Power Systems, shall be used to determine those facilities that are authorized emergency or standby generators. Consider damaged or inoperative generators as a source of spare parts. Com ponents and parts from several da maged generators may be reas- sembled to produce one usable machine. Equipment other than disabled generators may serve as a source of repair parts; e.g., inje ctors from a diesel e ngine in a destroyed ve hicle can be salvaged and adapted to a generator engine.

5.5.4.2.    Repairing Power Distribution System. Expedient repairs to power distribution systems are limited by the extent of damage involved and av ailability of spare parts. A large part of most electrical distribution systems is composed of non-repairable items such as poles, insulators, cross arms, switch gear, and in most cases, transformers. Only a few items within the electrical distribu- tion system lend themselves to repair. Items such as conduct ors, grounding wires, guy wires, anchors, service entrances, and occasionally transformers fall into this category.

5.5.4.2.1.     Conductors. Overhead power lines may need to be hung from trees, existing struc- tures or new poles. In some instances, cutting the damaged line on both sides of the destruction and bridging the area with new cable may be n ecessary. If it does not pose a danger , run the new power cable directly on th e ground. It can always be pr operly buried or elevated when time and resources are more available. Low-volt age distribution cables can be placed or run along the ground. Conductors that cross roads or pathways must be buried or protected by some means at the crossing. Figure 5.10. and Figure 5.11. show two different techniques for such crossings. The former displays a commercial cable protector bei ng used, and the latter shows how to protect cables using PVC and sandbags. The latter figure also has the cables on both sides of the road protected from foot traffic by sandbags. Schedule 40 Polyvinyl Chloride (PVC) conduit with a diameter of 3 to 4 inches is suitable for expedient raceways under cross- ings. In applications for which excessively high roadway temperatures are expected, Schedule 80 PVC should be used if available. For average temperatures over 90°F, the number of cables per raceway should be limited to three to prevent insulation overheating. In addition, the race- way in this application must also have at least 60 percent air space in its section to reduce the possibility of overheating.

Figure 5.10. Commercial Cable Protector Across Roadway.

5.5.4.2.1.1.     Cable Burial Requirements. As manpow er becomes available, the cables that were placed on the ground should be direct-buried to protect them from threat, equipment, and personnel damage; to prevent deterioration by the elements; and to improve their cur- rent- carrying ability. In moderate temperature locations, a burial depth of 8 inches for sec- ondary cable and 18 inches for primary cable is normally adequate. However , in sites where high temperature is anticipated, ensure that the secondary cable has at least 12 to 16 inches of cover.

Figure 5.11. Underground Roadway Crossing.

5.5.4.2.1.2.     Buried Cable Grounding. To save time and labor, distribution cables can be placed in trenches along with water and san itary lines. To reduce personnel exposure to electrical hazard, it is highl y advisable to place a bare c opper conductor in the trench alongside the cables if the cable does not have concentric neutral wires inside the cable jacket. This conductor must be bare and solidly attached to the generator ground terminal and to the f rames of al l connected electrical equipment. The size of the bare conductor should be close to the size of the largest insulated conductor in the trench.

5.5.4.2.2.     Grounding Wires and Rods. Proper grounding of elect rical systems is essential to the safe operation of the system. Grounding is most of ten accomplished by driving ground rods into the ground with a minimum 1/0 American Wire Gage (AWG) bare copper wire from the ground rod to either the device or systemto be grounded. The spacing and depth of ground rods depends upon the resistance to ground to the earth at the site. In the absence of the capa- bility to measure the resistance to ground and determine actual grounding requirements for the site, use a 3/4-inch diameter metal water pipe with at least 10 feet in contact with the earth, or a ground rod driven at least 8 fe et into the earth or into th e permanent ground water level, if known. Electrical continuity is essential in agrounding system; therefore, all connections must be clean and properly bonded. The design and application of grounding to an electrical system should normally be inherent inthe system installation and not something that is added at a later date.

5.5.4.2.3.     Guys (Wires and Anchors). Expedient repairs to guys usually involve replacing or resetting guy wires and anchors while raising new poles or br acing existing poles. In new work, guys should generally be installed before power line wires are strung. In reconstruction work, guys should be installed before making any changes in the line wires while at the same time being careful not to place excessive pu ll on the pole and wi res already in position. Improperly or inadequately guyed power lines will soon begin to sag, degrading the reliability of the line. When replacing guy wires, determine the condition of the pole before removing the old guy wire. If the pole is we ak, it should be securely bra ced before any changes in pole strains are made. Make sure the guy wire is installed so there is minimal interference with the climbing space on the pole, and guys should clear all energized wires. In some cases, it may be necessary to install a guy hook to prevent the guy from slipping down the pole. Position these hooks so they do not interfere with climbing and cannot be used as steps. Where guys are lia- ble to cut into the surface of a pole, protect the pole by installing a guy plate at the attachment point. The plate should be well secured to the pol e to prevent the possibility of injury to a worker climbing up or down the pole. When guys are installed near roadways, position them so they do not interfere with st reet or roadway traf fic. Guys located near streets should be equipped with yellow traffic guards (sometimes called “anchor shields”). Any guy wires con- taining snarls or kinks should not be used for line work, and it is preferable to use guy wires of the correct length to avoid unnecessary splices. The type of anc hor used in these repairs must provide suitable resistance to up lift and is therefore dependen t on the condition of the soil. Table 5.2. indicates suitable anchor types based on a range of soils from hard to soft. While the soil descriptions are not an i ndustry standard, manufacturers are familiar with this or similar classifications. For the majority of cases, the most suitable anchor is an expanding type ( Fig- ure 5.12.), because most lines are installed in ordinary soils.

Table 5.2. Anchors Suitable for Various Soils.

Figure 5.12. Expanding Anchor Details.

5.5.4.2.4.     Service Entrances. During the aftermath of an attack or disaster, it may become nec- essary to repair or build ne w service entrances with expedi ent methods and materials. New installations would be intended as temporary measures only and would be upgraded as the sit- uation stabilizes or used where the location isintended only as a one-time, short-term develop- ment. An electrical service entrance is the point at which electrical service enters a facility, and it normally consists of a main junction box, circuit breakers or fuses, and any other equipment located between the main junctio n and service drop, including meters. An expedient service entrance can be constructed as follows:

5.5.4.2.4.1.     If service entrance cable is available, a weather head can be formed with plas- tic electrician’s tape that will effectively seal moisture out of the cable insulation for a ser- vice entrance purpose (Figure 5.13.). Individually insulated wires can be bundled, tied with marline, and wrapped with tape to form a service en trance cable. Should plastic tape not be available, friction tape can be used to wrap the cabl e; however, if friction tape is used, it should be coated with varnish to render it waterproof before installation.

5.5.4.2.4.2.     Normally, split bolt connectors or compression splices will be used to connect the service entrance conductors to the service drop conduc tors. In an emergency where both conductors are solid, terminal loops can be turned in the conductors and a bolt with two washers can be used to make the connection ( Figure 5.14.). This type of connection should be taped on all hot conductors, but tape is not required for the neutral conductor.

Figure 5.13. Taped Weather Head.

Figure 5.14. Emergency Service Entrance Connection.

5.5.4.2.4.3.     If circuit breaker panels or mains are not available, using safety switches for service equipment can protect light loads. It may be necessary to bridge one set of contacts inside the switch so that the neutral will be a solid, unbroken circuit. The hot circuits can then be fused to the proper ampaci ty through the operating contacts ( Figure 5.15.). Keep in mind that this is an emergency situation and that the fuses should be well below the ampacity of the branch circuits installed to protect the ins ulation of these br anch circuits. Regardless of circumstances, some method must be provided to open all circuits within the structure with a maximum of five hand motions.

Figure 5.15. Safety Switch Used as Service Equipment.

5.5.4.2.5.     Transformer Repair. Expedient repair of transformers can be accomplished if the damage is not too extensive. Cracks or holes in the tank can be patched by welding, provided testing indicates that internal windings have not been compromised. T ransformers can be returned to service after beingthoroughly dried and replacing lost or contaminated oil. Keep in mind that oil from damaged transformers must be filtered be fore being reused and that motor oil is not a satisfactory substitute for transformer use (a transformer requires a highly refined mineral oil free from moisture or other impurities). In most case s, there will not be sufficient spare transformers available to provide a one-for -one replacement for damaged units. For example, you may not have a single-phase transformer with the capacity for the required load. In such a case, it may be necessary to parallel two smaller transformers in order to supply the load (Figure 5.16.). This expedient solution will solve an immediate problem, but it is not cost effective and should be replaced when the correct equipment becomes available. In a situation where three-phase power is n eeded and one transformer out of the three is damaged, three-phase power can still be provided by making what are commonly called open-delta con- nections. Figure 5.17. shows the open-delta connection wh en a four-wire, three-phase wye primary is involved. Figure 5.18. illustrates the connections that must be made to achieve the open-delta connection when a three-wire, three-phase delta primary is involved. Regardless of the type of primary involved, these connections are used only for emer gency situations and should not be constructed as per manent installations. The two transf ormers used in the open-delta connection will only supply 86.6 percent of their rated capacity. The total capacity of the bank will be only 57.7 percent of the original bank capacity.

Figure 5.16. Paralleling Single Phase Transformers.

Figure 5.17. Open–Delta With Wye Primary.

Figure 5.18. Open-Delta With Delta Primary.

5.5.4.3.    Repairing Interior Wiring. Expedient repairs to the interi or wiring of a structure depend on the extent of da mage and the criticality of th e facility. If the facility is not criti cal to current base recovery operations, delay repairs until additional resources are available. For facilities con- sidered essential to base operations, determin e the minimum level of required electrical service. Does an entire structure need power or only a small portion of it? What type of equipment will the electrical system of the building be required to support? Will it only need minimum electrical volt- age to provide lighting, or are th ere requirements for specialized voltages to power large air con- ditioning units, refrigeration units, or X-ray machines? For exam ple, there is no need to devote excessive manpower and materials to complete restoration of the base hospital’s electrical system if the hospital staf f needs only one section of th e building and one X-ray machine. In this case, electrical wiring in this section of the building could be restored and a special high-voltage cable could be run to operate the X-ray machine.

5.5.4.3.1.     When making expedient repairs to the interior wiring, use undamaged wiring to the maximum extent possible. This will cut repair time and r esult in fewer exposed live circuits when the facility is returned to operation. As with distribution systems, damaged areas can be bypassed with new wiring to complete a vital circuit.

5.5.4.3.2.     When bypassing damaged areas or running temporary lines into a structure, wiring can be run across floors and other building surfaces to expediterepairs. However, if the facility will have a high volume of pers onnel traffic, tack the wiring to the wall or ceiling to prevent further damage or hazards. The temporary wiring does not have to be conc ealed to present a finished appearance; it only needs to be functional and out of the way of heavy traffic (Figure 5.19.).

Figure 5.19. Installation of Temporary Interior Wiring.

5.5.4.3.3.     Another important consideration in the expedient repair of in terior electrical sys- tems is the supply of wiring, switches, and a ssociated hardware needed to make repairs. Depending on the extent of damage, base supply sources may not have adequate levels to pro- vide for all repair needs. In these cases, cannibalization and substitution become very impor- tant. At theater locations, many components will be of foreign manufacture and not readily available through US supply channels, making it imperative that repair crews salvage as much as possible. Structures declared irreparable may contain switches, wiring, and other hardware that can be u sed to restore electrical services to other structures. A note of caution: do not inflict additional or unnecessary damage during salvage attempts. S tructures being salvaged may have to be rehabilitated in the future.

5.5.5.    Foreign Wiring Systems. Another type of contingency situation involves reactivating an estab- lished installation in a foreign country. In this case, the facilities on the installation would be intact but possibly requiring renovation or modifications.

5.5.5.1.    Foreign Systems Interface. The primary di fference between US and foreign wiring sys- tems is that most foreign systems have not be en installed according to the standards outlined by the US National Electric Code (NEC). This fact may be attributed largely to the material shortages in many foreign countries, particularly economica lly depressed nations, which have dictated the use of materials at hand. Additional details rega rding material variances and electrical system comparisons are described in the following paragraphs.

5.5.5.1.1.     Voltage. The U.S. uses nominal voltages th at range from 120 to 240 volts for sin- gle-phase alternating current (AC) and 208 to 600 volts for three-phase AC in low-voltage dis- tribution systems. A considerable number of foreign countries use other voltages, requiring our electrical equipment to be converted, modified, or operated inefficiently when powered by these foreign electrical systems.

5.5.5.1.2.     Frequency. The standard frequency of AC distribution in the US is 60 Hertz (Hz). In many foreign lands, 50-c ycle frequency generation is common; but the electrician may also encounter frequencies such as 25, 40, 42, and 100 cycles. General guidelines for using 60 Hz electrical equipment on 50 Hz power sources is provided in paragraph 5.5.5.4.

5.5.5.2.     Expedient Procedures Involving Foreign Systems. During contingency operations in a foreign country, the Air Force may use all or part of an electrical system on a foreign installation. Though the decision of employment is largely determined by the immediate circumstances, the Air Force electrician or unit commander will foll ow one of two general procedures as outlined below.

5.5.5.2.1.     Since the electrical components of a fo reign and domestic electrical system cannot be interchanged, the decision may be made to use all foreign equipment. The obvious problem in this decision is one of supply. The parts needed may not be readily available.

5.5.5.2.2.     If time is a consequential factor , consideration should be given to the use of stan- dard electrical items made in the US and the modification of plugs or connections so that they may be used in the foreign sy stem. Although this method usually results in decreased operat- ing efficiency, the ease of adaptability and abundance of supplies usually outweigh the reduc- tion in performance.

5.5.5.3.     Different Voltage Effects. Whenever possible, all equipment should be operated at its rated voltage. To expedite foreign system use, items built to operate at standard American voltages may have to function at dif ferent voltages. Though such items may not be operated ef ficiently, their availability for use may bean important military need. Some effects of voltage differences on common electrical devices are explained below.

5.5.5.3.1.      Lighting Fixtures. When fluorescent lamps are operated at voltages higher than standard, both the lamp and ballast life are shortened. Line voltages below the minimum of the operating ranges of 110-125, 199-216, or 220-250 vo lts will cause uncertain star ting, short lamp life, and reduced lighting efficiency. When incandescent lamps are used and operated at voltages higher than their rati ngs of 114, 120, and 125 volts, they also have a shortened lamp life below that expected; but their light output is increased. Conv ersely, if the line voltage of operation is below standard, the life of the la mp is increased; but the lighting ef ficiency is reduced approximately 3 percent for each 1 percent drop in rated voltage.

5.5.5.3.2.     Motors. Ro tating equipment, such as motors an d fans, is usually manufactured to operate with a permissible volta ge variation of 10 percent with in their prescribed rating. The combined voltage and frequency variation is al so limited to 10 percent. Higher voltages give increased torque, increased ef ficiency, and increased starting temperature. Operating at volt- ages differing from rated voltages by more th an 10 percent may be permitted only in an extreme emergency since the eq uipment may be damaged or ev en destroyed by such ope ra- tions.

5.5.5.4.    Different Frequency Effects. Electrical operating items based on resistance characteristics (such as heaters, hot plates, and electric sto ves) operate efficiently over all ranges of distribution frequencies used throughout the US and foreign territories. Rotating equipment and items such as lights and transmission or receivi ng equipment are adversely affected by variations in frequency. Some of the effects of frequency changes on this type of equipment are described below.

5.5.5.4.1.     Resistive Load s. Fluorescent lights rated to oper ate at a nominal 60-cycle current can be used at 50 cycles, but with a shorter ball ast life. At lower than 60-cycle frequencies, a noticeable flicker in the light output can be de tected. This is undesirable where painstaking and meticulous work is being performed. Operation at lower frequency is not satisfactory and should be avoided. Incandescent lights, because of their resistance design, will operate satis- factorily at all of the freque ncies encountered overseas. However, lamps designed to function at 60 Hz will not burn as brightly at 50 Hz and ovens will not be as hot.

5.5.5.4.2.     Static Induction Devices. Distribution transformers, electric discharge lighting bal- lasts, series lighting current regulators, and other static inductive equipment induce magnetic energy fields in iron as part of their normal operation. The magnetic flux density is directly proportional to the volts/hertz ratio of the pow er source. Consequently, the voltage must be reduced proportionally to maintain the volts/hertz ratio at the design point.

5.5.5.4.3.     Transmitting Equipment. All receiving and transmitting equipment, or other items which have transformers included in their wiring, will not operate satisfactorily either below or above their rated line freque ncy and should be used only in an emergency. In some cases, there may be frequency converters available, part icularly in flight line operations, which can be obtained and used when the equipment operation is mission essential.

5.5.5.4.4.     Induction Motors. Induction motors rated for 60 Hz operation will run at about 5/6 of rated speed when connected to a 50 Hz source. Consequently, if a motor is nominally rated to run at 1800 rpm at 60 cycles and is operated at50 cycles, its output speed will be reduced to approximately 1500 rpm. Motor current varies inversely with both source frequency and volt- age. As the 50 Hz source voltage is reduced, motor current heating the winding increases while iron loss heating is decreasing. No amount of voltage reduction can compensate for both heat- ing effects simultaneously. However, induction motors rated at 120V, 60 Hz will operate suc- cessfully at about 110V, 50 Hz if the speed reduction can be tolerated. Keep in mind that some motors are built to function at either 50 or 60 cycles.

5.5.5.5.     Electric Motor Voltage/Hertz Variation Remedies. Corrective me asures for two of the more common major electric motor problems re lated to voltage and he rtz incompatibilities are provided below.

5.5.5.5.1.     Motor Heating Due to Iron Saturation. Motor geometry establishes a design volts/ hertz ratio. As addressed earlier, if the motor will be operated at less than designed frequency, then the voltage must be reduced proportionately (5/6) to maintain the vo lts/hertz ratio at or below the design limit.

5.5.6.     Miscellaneous Reference Ma terial. The next few page s list reference information regarding load-carrying capacity of wire, load current and circuit breaker sizes for AC motors, a description of common AWG wire sizes, types, and general uses along with pole sizing and setting specifications.

5.5.6.1.    Wire Size and Voltage Drop Determination. The size of wire for a given section of a sys- tem is selected based on the amount of electrical load that it must carry and on the allowable volt- age drop. Note the larger the wire size, the greater its capacity and the less resistance it will have, hence, less voltage drop. Economy, however, should be considered in size determination. Table

5.3. shows the KVA (kilovolts-amperes) and current-carrying capacities for wires ranging from No. 8 to a 4/0. In addition, Table 5.4. lists current and circuit breaker sizes for AC motors.

Table 5.3. KVA Load-Carrying Capacity of Wire.

Table 5.4. Full-Load Current and Circuit-Breaker Sizes for AC Motors.

5.5.6.2.    Conductor Types. Conductors used in installation overhead distribution systems are usu- ally copper, although they may be steel, aluminum, or combinations of these metals. Figure 5.20. provides information regarding common AWG wire sizes, types, and app lications. In addition, Table 5.5., Table 5.6., and Table 5.7. list the wire sizes for 120-volt, single-phase circuits, number of wires allowable in various conduits, and th e wire sizes for 240-volt, single-phase circuits, respectively. Lastly, Figure 5.21. shows four of the more common wire splice techniques in use today.

5.5.6.2.1.     Copper Conductors. Copper has high conductivity and is easily spliced. Hard-drawn or medium-hard-drawn copper is desirable for distribution conductors because of its strength. Since heating and cooling redu ces the wire’s tensile stre ngth from 50,000-psi to 35,000-psi, soldered splices should not be used on hard-drawn copper wire because the hot solder weakens the joints. Splicing sleeves are normally used when making joints.

5.5.6.2.3.       Weatherproofing. Triple-braid weatherproofing is preferred to double braid. Improved types of weatherproofing include plastic covering and layers of impregnated unspun cotton or impregnated rubber filler. Before these newer type coverings are used, approval should be obtained from the higher command having jurisdiction.

Figure 5.20. Wire Sizes, Types, and Uses.

5.5.6.2.4.      Primary Distribution. For primary distribution below 5,000 volts, either bare or weatherproof conductors may be used. The ordina ry weatherproof covering is not to be considered as insulation, although it does prevent breakdowns on the lower primary voltages caused by conductors swinging together . For all primary distribution over 5,000 volts, bare conductors are ordinarily used.

5.5.6.2.5.     Secondary Distribution. Weatherproof wires are us ed for secondary distribution. The weatherproof coveri ng is an ef fective insulation for secondary voltages, permitting rack-type distribution and closely spaced secondary conductors. No wire smaller than a No. 8 should be used for secondary distribution or for any external transmission of power.

Table 5.5. Wire Sizes for 120-Volt, Single-Phase Circuits.

Table 5.6. Number of Wires Allowable in Various Sized Conduits.

Table 5.7. Wire Sizes for 240-Volt, Single-Phase Circuits.

Figure 5.21. Common Wire Splices.

5.5.6.3.    Overhead Distribution Pole Requirements. Atestablished installations, electrical distribu- tion lines are often overhead, supported by poles or strung from building to building. As a general rule, lines carrying over 240 volts are supporte d on poles while those carrying 120 to 240 volts may be supported on masts or insulators attached to buildings. Service wire s should be kept a t least 3 feet from windows and 8 inches above flat roofs. Since theater of operations electrical dis- tribution systems are exclusively overhead systems, wooden poles similar to those used in civilian construction are used to carry the conductors. Unlike civilian construction, cross arms are not often used at overseas installa tions. Instead, conductors are hung directly on the pole, one above the other.

5.5.6.3.1.     Pole Selection. The poles used in a distribution system should consist of a good grade of timber that will last. Good pressure-treated Texas southern pine, for example, can be expected to last 35 to 50 years. Conversely, untreated local timber such as soft pine may last only a couple of years and have a useful life of only one season under unfavorable conditions. However, the fact that a pole is in good condition is not proof that it can satisfactorily support the line. Poles must withstand column loadings aswell as transverse loads from wind and turns in the line.

5.5.6.3.2.     Pole Height and Class. Table 5.8. shows the required hei ghts and classes of poles for various types of loadings in military installations. The smaller a class number the sturdier the pole. The class of a given pole depends on its length, di ameter, and the materi al from which it is made. The height is governed by restrictions both above and below the proposed conductors. Near airfields, poles must be kept low, yet high enough to provide adequate clear- ance over streets and roads. Co rner poles, transformer poles, and the like are usually one or more classes heavier and sometimes 5 feet higher than line poles. Table 5.9. gives the required classes for transformer poles.

Table 5.8. Height and Class of Power Poles.

Table 5.9. Power Pole Size for Transformers.

5.5.6.3.3.     Vertical Wire Spacing. Vertical wire spacing i s the clear distance between wir es. Six-inch minimum spacing is re quired for spans up to and incl uding 200 feet while 12-inch minimum spacing is required for spans over 200 feet. A clear space is always left at the top of an electrical pole. This distance is equal to the wire spacing, that is, 6 inches for 200-foot spans and less and 12 inches for spans greater than 200 feet.

5.5.6.3.4.     Setting Poles. Poles should be set deep enough to develop their full bending strength at the ground line. Table 5.10. gives the recommended setting de pths in soil and in rock. The actual setting or installation of the poles is done by one of three methods: by hand, with a crane, or by using a nearby pole as a gin pole.

Table 5.10. Power Pole Setting Depths.

5.5.6.3.5.     Clearances. Minimum clearances of conductors over ground, rails, and other objects are given in Figure 5.22. Special consideration must be gi ven to railroad yards and material handling areas. Allow a minimum horizontal clearance of 11 inches from the outside face of a curb or roadbed to the face of the pole to prevent damage by vehicles. The clearances shown may be decreased in theater of operations construction where safety factors are reduced. The engineer officer must use sound judgment in establishing minimum clearances for a given project, taking into account materials available, military necessity, urgency of the project, and other factors.

Figure 5.22. National Electric Safety Code (NESC) Minimum Clearances.

5.5.6.4.    Frequency and Voltage Data. Different power frequencies and voltages are used in differ- ent parts of the world. In the US, 60 Hz is themost common frequency and secondary distribution voltages of 120/208, 120/240, and 277/480 are common. Table 5.11. provides an extensive list of frequencies and secondary voltages for commercial power systems in many foreign lands and US territories. This data is subject to change so always verify before beginning work.

Table 5.11. List of Frequencies and Voltages.