In-Situ Grouting at ID Nat’l Lab Radioactive Waste Mgmt Complex (TPD1101019)

In accordance with the project specification (SPC-1162), the system was to be equipped with drill-string contamination-control hardware. Prior to construction, the HBI’s design was submitted through the CWI vendor data system and was thoroughly reviewed by RadCon and safety professionals.

The shield assembly mitigated the potential spread of contamination as the drill string was lifted from an insertion point, as it moved positions, and it was inserted into a position. The shield assembly was supported over the immediate area of the hole being drilled by an enclosed foot at the base of the mast. The assembly included a top sleeve, which contained a set of heavy-duty wipers to remove the grout from the drill string as it was withdrawn through the plate, and a spray head. The spray head was supplied from a reservoir and pump mounted on the rig, which applied a coating of fixative to the rotating monitor as it was withdrawn. CWI RadCon personnel fabricated a heavy drawstring sack that was placed over the entire assembly for transport of the rig between ISG sites. In addition, RadCon personnel routinely covered the hydraulic jaws with plastic for additional protection. The entire assembly was bolted to the base of the mast, below the jaws, and was designed to be removed and discarded at the completion of the job. Figure 8 shows the contamination control hardware mounted on the base of drill rig mast.

2.3.3.1.1               Grout Mixing—Grout was mixed using the batch plant. The silo was filled by first placing the super sack on a stand and replacing the factory string that closed the chute on the bottom with a zip tie. The sack was then lifted into place over the silo and the zip tie was cut, releasing the binder material into the silo. The binder material (dry grout mixture) was transferred from the silo into the mixing tub of the batch plant, and the appropriate amount of water was added to achieve the desired ratio of cement to water. Grout was mixed until it met specifications.

2.3.3.1.2                Drilling—The driller maneuvered the mast until the data logger indicated the bit position was within 0.2 ft of the preprogrammed ISG insertion point coordinates. The driller recorded the unique insertion location identifier (Column ID), and date on the HBI jet grout production log. He then visually confirmed the work area was clear and lowered the bit until it was even with the ground surface. Grout flow was then initiated under low pressure (trickle flow) supplied by the batch plant. After grout trickle flow was observed, drilling began using both percussive action and rotation at the driller’s discretion. The bit was inserted approximately 2 ft bgs after which the driller actuated the touch screen control in the cab of the drill rig to allow power to the high-pressure pump. He then contacted the pump operator via radio and instructed him to engage the pump for low-pressure grout injection. Drilling was advanced to the target depth of 17 ft bgs for waste trenches or 25 ft for the soil vault location, or until refusal was met, whichever came first. If refusal was encountered at a depth greater than 4 ft bgs or target depth was reached, high-pressure grouting began. If refusal was encountered at a depth less than 4 ft bgs, the location was abandoned and the rig was moved to the next insertion point. Refusal was defined as 29  seconds of vigorous drilling with less than 2 in. of penetration. The 30-second hold point was developed to ensure each insertion point was drilled to the maximum achievable depth.

2.3.3.1.3               Grouting—Upon achieving total depth, the drill rig operator communicated with the pump operator to initiate the high-pressure grouting system and initiated the automated DAS. Prior to initiating flow, the pump operator visually confirmed and communicated that the high-pressure safety area was clear and the protective shielding was installed around the high-pressure pump outlet. He then slowly brought the pump up to an operating pressure of 5,500 psi while observing pressures and flows. The driller then rotated the drill string for 30 seconds with no retraction to ensure grout flow to the nozzles after which he began drill string retraction. During this operation, the drill rig operator manually recorded grouting start and stop times and associated footages, total gallons delivered, and rate information from the DAS readout in the cab of the drill rig to complete the jet grout production log for the insertion location.

To protect the safety of personnel and prevent damage to drilling components in a lightning take cover occurrence, the option to flush material into a non-waste-bearing subsurface location was

exercised. In each instance, project technical support personnel identified a location outside the treatment site to conduct the operation. Once the monitor was in position, it was drilled to total depth. Water was then pumped via the high-pressure pump (pressure range between 500 and 1,500 psig) through the system and out the monitor as the monitor was raised and lowered and rotated to dissipate the flush water.

Following displacement of the grout with fresh water, the drill rig operator ensured the high-pressure pump was deenergized, the drill string was raised to the surface, and clean water was observed exiting the nozzle indicating the system was clean. In each instance, following the emergency situation, the resultant penetration was plugged by tremieing grout product to the surface over its entire length. Prior to the drill rig and mast flush operation, the high-pressure pump and supply hosing were disconnected from the rig and flushed separately into the excess grout basin by the crew to minimize the amount of material being directed through the nozzle port.

In conjunction with both system flush operations, the batch plant operator washed the inside and outside surfaces of the batch plant with minimal fresh water. Displaced dilute grout and water from the mixing plant and residual flow through the high-pressure pump and supply lines were directed onto the adjacent ground surfaces or into local drainage. Following mobilization of the support equipment, remaining residual material was scraped off the surface and disposed of.

2.3.3.1.1                End of Shift—Following flush operations, HBI personnel proceeded to download data acquisition files from drill rig, place the equipment in a safe configuration, shut down equipment, and put away tools.

1.1        Deviations from the Phase 2 Work Plan

The Phase 2 Work Plan (DOE-ID 2010) acknowledged that modifications could be required during implementation of ISG and outlined a flexible process to manage change (see Section 1.4 of the Work Plan). That process was invoked several times. None of the changes affected location-specific remedial designs, and each site was treated in accordance with its remedial design without deviating from the planned treatment footprint and number of grout insertions. Neither was any change so significant that it warranted revision of the Work Plan. Agency representatives concurred with these modifications in conference calls or site visits, as allowed by the Work Plan. The Agencies formalized their agreement through review of this interim completion report. As required, this report documents the changes.

One change to the waste management strategy was identified and discussed among the Agencies during a conference call (March 1, 2010) before ISG mobilized. As agreed, excess clean grout from ISG daily operations was disposed of in grout returns basins within the SDA. This approach is a minor change from the original plan to dispose of clean excess grout outside of the SDA (Table 5-1 of the Phase 2 Work Plan).

The drill system design was slightly modified after a nozzle was damaged during the MSA at the cold test pit. As discussed with the Agencies (June 7, 2010), investigation concluded the nozzle orientation, which was 15 degrees down from horizontal, caused the damage. Horizontal nozzle orientation was implemented to prevent further problems. This decision constituted a change to Item 19 in Section 3.1.4.1 of the Phase 2 Work Plan.

A field decision, defined as “…real-time refinements to ISG-site-specific location designs or to ISG operating parameters” (Section 4.4.3, DOE-ID 2010) was adopted after ISG operations began. After careful review of operating data, the Agencies concluded during a conference call (August 12, 2010) that exceeding the upper-bound retraction rate was an acceptable condition arising from efforts to minimize grout returns in keeping with the ISG safety basis. ISG operations were to remain within the operating parameters specified in Section 3.1.4.1 of the Work Plan to the maximum extent practicable; however, deviations—such as to a higher retraction rate (Item 20b in the Work Plan)—were allowable to reduce grout returns. Such changes could not jeopardize the overall ISG performance objective (i.e., at least 80% of the maximum potential volume for the ISG site). (Note: ISG exceeded the performance objective at each location.)

1. 3.                CHRONOLOGY OF EVENTS

The OU 7-13/14 ISG Project was separated into specific work elements for implementation of the Phase 2 remedial action. The chronology of these elements form the basis for detailed discussion of the work presented in Sections 3.1 through 3.9 as follows:

• Section 3.1—Selecting a Vendor
• Section 3.2—Offsite Demonstration
• Section 3.3—Site Preparation
• Section 3.4—Management Self-Assessment and Authorization to Deploy
• Section 3.5—Mobilization
• Section 3.6—Remedial Action
• Section 3.7—Pre-Final Inspection
• Section 3.8—Phase 2 Close-Out
• Section 3.9—Post-Construction Operations and Maintenance.

3.1        Selecting a Vendor

The procurement strategy for ISG was modeled after the successful beryllium grouting project executed in the SDA in 2004 (Lopez et al. 2005). The project was performed as a construction job with a subcontractor drilling and grouting and ICP providing support functions.

A pre-solicitation notice for vendors interested in the job was published on the Federal Business Opportunities Web site April 29, 2009. Interested parties were requested to respond no later than May 22, 2009, after which time a directed request for proposal process was conducted. The request package included the Statement of Work, Special Conditions, the Construction Specification, and General Provisions. On October 1, 2009, the request for proposal was issued on a competitive basis to 12 potential vendors with a proposal due date of November 2, 2009. A pre-bid conference and tour was held at the RWMC October 13, 2009. Sixteen subcontractor representatives attended the conference, which included presentations by contractor representatives on safety, quality, RadCon, labor relations,f and construction. Two addenda to the request for proposal were issued before the proposal due date and five proposals were subsequently received.

A team of four project personnel evaluated proposals based on an Evaluation Plan (ICP 2009) developed specifically for the project. After the proposals were evaluated, a third addendum to the request for proposal was issued clarifying bid quantities and providing questions and comments specific to each vendor. All five vendors responded. The technical evaluation was performed without knowledge of bid price and all proposals were ranked. After the technical evaluation was complete, price was evaluated and the best overall value to the government was determined. On December 10, 2009, the subcontract to execute construction services for the Phase 2 OU 7-13/14 ISG Project was awarded to HBI.

HBI is a subsidiary of the Keller Group, a large, worldwide independent ground engineering specialist. HBI is the largest of the Keller Group’s geotechnical companies and one of the prominent geotechnical contractors in North America.

3.1        Offsite Demonstration

In accordance with the project specification (SPC-1162), HBI was required to conduct a CC/SO test with the drilling and grouting system developed for use at the INL Site. Testing was conducted to a CC/SO Test Plan (VDR-300568), which was managed through the CWI vendor data system. HBI was required to conduct these tests using procedures developed for reference in INL Site work documentation. The purposes of this test were for HBI to (a) demonstrate equipment configuration and operability consistent with the approved system design and (b) develop and demonstrate the ability to perform the grouting operations to the requirements of the Phase 2 Work Plan (DOE-ID 2010).

The demonstration consisted of the following test elements: an operational system pressure test, a grout operations test, and grout placement qualification. The demonstration mirrored, to the extent possible, the grout operations to be performed at the SDA. After the demonstration, an HBI report documented the demonstration and listed revisions to the equipment configuration or system operation (VDR-306854). On April 14, 2010, the offsite demonstration was conducted at the HBI facility in Santa Paula, CA.

3.2.1             Test Pit Construction

The offsite demonstration simulated waste pit was constructed to meet the specifications of the CWI-supplied engineering design file (EDF-9512). The Engineering Design File provided direction for preparing surrogate containerized buried waste forms and subsequent placement of surrogate waste in the test pit; this simulated project-specific buried waste sites located within the SDA. The pit design allowed for demonstration of all test objectives. The ICP Waste Information and Location Database provided the design basis for surrogate waste formulation, container type, and associated loading ratios.

Buried waste container types consisted of 2- × 2- × 2-ft cardboard boxes, 4- × 4- × 2-ft plywood boxes, and 55-gal metal drums lined with appropriately sized 4-mil polyethylene bags. Additional container types included 5-gal steel drums or canisters and 1-gal paint cans. Each container was loaded with a specific surrogate waste type. Surrogate waste types included combustible (e.g., paper, wood, asphalt, and plastic) and noncombustible debris (e.g., assorted metal scrap and glass) and surrogate sludge containing kitty litter. The container was packed with equal amounts of each surrogate waste (i.e., manually compressed material) until full. Containers were taped closed and/or covered and sealed. Table 5 contains information on individual containers and the associated surrogate waste types placed in each. Note that not all surrogate waste types were placed in all containers.

The test pit dimensions were 4.5 ft wide × 7 ft long × 13 ft deep. The bottom of the pit was lined with concrete riprap and steel to simulate absolute refusal. Placed above the base were four 2-ft-thick surrogate waste form layers separated by soil and loose debris, consisting of scrap metal, combustibles, gravel, and asphalt. The total thickness of the surrogate waste seam was 9 ft. Waste forms were strategically placed into the excavation to simulate a random dump while maintaining a record of placement for later reference. Figure 19 shows a schematic of the CC/SO test pit construction.

The placement of surrogate waste followed the design identifying the location of each surrogate waste form placed in the pit. Figures 20 through 23 show the distribution of the surrogate waste containers in the CC/SO test pit at various depths. Layouts in the figures are shown in four 2-ft layers, from the bottom up. The pit was capped with a 1-ft layer of overburden soil, 1-ft layer of hardpan soil, and another 1-ft layer of overburden soil. The hardpan soil was clay material that was compacted to represent the hardpan layer within the SDA. Surrounding the test pit was a 1-ft berm constructed to represent the grout returns basin.

Table 5

Figure 19. Schematic of component checkout/system operational test pit construction.

Figure 20. Layout of Layer 1 of the component checkout/system operational test pit (0–2 ft from bottom of the pit).

Figure 21. Layout of Layer 2 of the component checkout/system operational test pit (2.3–4.3 ft from bottom of the pit)

Figure 22. Layout of Layer 3 of the component checkout/system operational test pit (4.6–6.6 ft from bottom of the pit).

Figure 23. Layout of Layer 4 of the component checkout/system operational test pit (7.9–8.9 ft from bottom of the pit).

• Equipment and personnel positioning and travel relative to simulated RadCon barriers
• Monitor fixative spray
• Monitor wipers
• Contamination control plate and base assembly.

3.2.1.2.6                 Data Acquisition and Logkeeping- During the demons tration, HBI demonstrated the fonctionality of the DAS and manually recorded drilling and grout specific gravity logs. DAS data were recorded and submitted in presentation fonn upon completion of the test. Table 6 presents a summary of DAS output parameters. Manual drilling logs were reviewed to verify they were comparable with the automated system.

Table 6

Though the operation was determined to be effective, ICP Safety and RadCon representatives observed several steps that were cumbersome or presented safety concerns and presented mitigations to HBI for incorporation into their operating procedures. However, an operational refinement was identified involving flushing grout to grout returns and excess grout basins. Clean excess flush water was discharged to SDA ditches. Section 3.6.2.1 discusses adoption of this alternative in more detail.

3.2.1.1.2               Nozzle Change-Out—During the grouting demonstration, occasional plugging required changing a nozzle. Impurities in the neat grout caused the nozzle plugging. Assessments of the in-line filters and material behind the plugged nozzle identified plastic webbing fragments introduced into the mixture from opening the super sacks directly over the binder silo (see Figure 29). Solidified binder fragments also were observed, which originated from staged super sacks exposed to heavy rains. The sacks were not waterproof; thus, areas of the binder material became hydrated, were then cured, and subsequently were introduced into the grout mix when the affected sack was loaded into the silo.

Figure 24. Nozzle decontamination.

Figure 25. Placement of the monitor sleeve

Figure 26. Positioning the monitor over the flush tank.

Figure 27. Flush water exiting the nozzle port.

Figure 28. Site view of the containerized flush operation.

Figure 29. Low-pressure grout system filters plugged with super sack webbing material.

Nozzle change-out also was required in separate instances because of pressure losses from galling of nozzle threads. Abnormal wearing of the nozzle and adjoining monitor threads, observed in the 15-degree nozzle port configuration, was caused by an extension of the nozzle insert into the annulus of the monitor. The extension interrupted grout flow and abraded the nozzle threads.

During grout operations tests, nozzles were changed according to procedure without imposing radiological protection measures. A thorough evaluation of the spot decontamination and accompanying nozzle change-out procedure, with radiological measures, was conducted as part of the separate system flush evaluation and determined to be successful.

3.2.1.1              Grout Placement Qualification. The third test element consisted of grout placement qualification. HBI provided operational data and drilling log information so the project team could evaluate the post-grout-injection qualification process and demonstrate the effectiveness of the successful placement of grout. In addition to the data provided by the DAS and logs, the grout qualification required a portion of the test pit to be exposed. This requirement called for the top 4 ft of the test pit to be removed, exposing the top portion of the grout columns. Along with the top 4 ft being removed, the front edge of the grouted area was exposed and inspected. The inspection verified that, given the grouting parameters, a competent monolith was created. Figures 30 through 34 show the process of exposing the monolith, exposed sections of the monolith, a single grout column measured at nominally 26 in. in diameter, and samples of treated debris taken from the monolith.

3.2.2             Test Configuration Certification

After completion of the offsite demonstration, HBI was required to submit a report documenting the demonstration and listing needed revisions to the equipment configuration and system operating procedures. These changes were documented and tracked. When equipment was delivered at the INL Site, HBI was required to provided a Test Configuration Certification (VDR-307812) documenting that the final operating procedures and equipment test configuration were not modified, except as documented and approved by the CWI project engineer. Table 7 contains system design and operational changes that were implemented during and after the offsite demonstration.

3.2.3             Conclusion

HBI drilled and grouted 10 test holes for the offsite demonstration test. This test demonstrated all procedures addressed in the Drilling and Grouting and O&M Plans, from the pre-job briefing to clean-out. HBI pumped a total of 1,592 gal of grout and created a competent grouted structure that encapsulated the surrogate waste and associated soil in the test pit.

Some issues were noted during the test. The containerized equipment flush operation was problematic. DOE, CWI, and DEQ representatives, present for the test, agreed that observed potential safety issues outweighed advantages of transferring flush water into containers outside the contamination area. Post-testing conversations involving Agency and CWI representatives concluded with a decision to flush water directly to the ground surface (see Section 3.6.2.1). CWI and DOE representatives discussed lessons learned, observations, and potential corrective actions with the HBI operations crew and technical staff. The test report recorded primary modifications to the equipment and procedures. Comprehensive operational, design, and hardware modifications were documented and approved through submittal of

the Test Configuration Certification (VDR-307812) prior to mobilization to the INL Site. The MSA (see Section 3.4) verified implementation of such modifications before start of construction on the INL Site.

Tests showed that the equipment, procedures, and personnel performed as planned and ICP judged the offsite test successful.

Figure 30. The process of exposing the monolith in the simulated test pit at Hayward Baker’s facility in Santa Paula, CA.

Figure 31. The process of exposing the test monolith.

Figure 32. Exposed top layer and front cross section of the test monolith.

Figure 33. A single grout column measured at nominally 26 in. in diameter.

Figure 34. Samples of treated debris taken from the monolith.

Table 7

3.3        Site Preparation

Site preparation involved work performed in advance of subcontractor mobilization to facilitate construction at Cold Test Pit-South and ISG sites in the SDA. Construction work was performed in accordance with the approved project-specific health and safety plan, ICP work control documents, and Phase 2 Work Plan (DOE-ID 2010).

3.3.1             Cold Test Pit-South

HBI’s onsite demonstration at the Cold Test Pit-South (see Figure 35) supported the MSA to show that HBI and CWI personnel were ready for operations and to demonstrate acceptable proficiency of the jet-grouting design and operational procedures. The test pit was constructed in 1988 to provide a cold nonradioactive/nonhazardous test bed to conduct treatment and retrieval technology demonstrations. A series of test cells were constructed and filled with simulated waste and backfilled in the same manner in which RWMC waste was disposed of between 1953 and 1970 (BWP-ISV-009). Zone 2, a stacked drum region of the test pit, was selected for the demonstration. The site was grubbed and backfilled to provide a stable, level working surface. Areas for equipment unloading and parking were identified and the vegetation removed. Barriers and postings were improved and replaced around the perimeter of the test pit with current project information. A wide perimeter around the simulated test pit was fenced and posted as a construction barrier, and caution and warning zones were marked for the ISG operation.

The site was surveyed using a Leica System 1200 global positioning system and marked. A grout returns basin was excavated to support testing operations for both HBI Rig #1 and Rig #2. Rebar was driven 2 ft into the ground at the corners of the ISG site boundary. Aluminum survey caps, slightly elevated above the ground surface, were placed on top of the rebar. Once all of the survey caps were installed, as-built coordinates were collected. These point data defined the ISG sites on the ground surface and were used to generate an as-built geographic information system data layer for siting insertion points. CWI provided HBI with coordinates for each insertion point location within the test pit so locations could be preprogrammed into their positioning system and DAS database (see EDF-9531). A significant number of points were laid out to provide HBI an opportunity to test their hardware to the extent necessary. Site diagrams and coordinates for each insertion point are contained in Appendix A.

3.3.2             Subsurface Disposal Area

Site preparation within the SDA included establishment of the ISG sites, construction of the project infrastructure, and coordination of operational activities with RWMC facility management and ongoing projects within the SDA.

3.3.2.1              ISG Sites and Insertion Points. The Phase 2 Work Plan (DOE-ID 2010) documents the process by which the optimized ISG location designs, with definitive buffer areas, were established. Through this process, treatment areas were reduced while increasing the total curies of releasable Tc-99 and I-129 that were treated. Grouting the injection pattern (e.g., 20-in. center-to-center) at each trench location buffered each site by 3.5 ft on the ends and by 2 ft on the sides, equating to two grout columns of buffer on each end and one grout column on each side beyond the actual trench width. The soil vault location was ringed by a grout wall approximately 2 ft thick. Prior to HBI mobilization, coordinates for the 21 ISG sites were surveyed using a Leica System 1200 global positioning system with horizontal accuracy of ±1/4 in. Rebar was driven 2 ft into the ground at the corners and intermediate points along the ISG site boundaries. Aluminum survey caps, slightly elevated above the ground surface, were placed on top of the rebar (Figure 36). Once all of the survey caps were installed, as-built coordinates were collected and the survey caps were stamped with unique codes. These point data defined the ISG sites on the ground surface and were used to generate an as-built geographic information system data layer for siting insertion points.

Figure 35. Simulated in situ grouting site at the Cold Test Pit-South.

A trigonometry calculator was used to calculate the 20-in. triangular-pitch matrix coordinate offsets where x,y for A = (0, 0), B = (0, 20), and C = (10, 17.3). These calculations were used in Excel to generate a template of insertion points that was wider and longer than the largest ISG site. Using ArcMap geographic information system software (ArcGIS 2008), this template was copied, moved, and rotated to fit each individual ISG site established by the as-built geographic information system data layer. Excess insertion points that fell outside of each ISG site were deleted. Each insertion point was documented with the ISG site name, the insertion point name (i.e., insertion waypoint ID), and easting/northing coordinates. Easting/northing coordinates were calculated automatically by the ArcMap geographic information system software. Appendix B includes site diagrams and coordinates for each corner and intermediate points along the ISG site boundaries and insertion point coordinates and detailed site diagrams for each site.

Figure 36. In situ grouting site boundary aluminum survey cap.

 

3.3.1.1              SDA Infrastructure. To support grouting operations, a project administrative and laydown area was constructed comprising the following actions: siting and setting up temporary office trailers, parking areas, equipment and material laydown areas, and a temporary CERCLA waste storage area.

ISG Project personnel worked with facility representatives to establish interfaces for road outages, traffic flow, and shipment patterns and schedules; ARP IV project engineers to establish ISG application scheduling and final elevation requirements in ARP footprint areas; SDA system engineers to place new abovegrade fire protection system; and other activities (e.g., vapor vacuum extraction and environmental monitoring) to minimize impacts to ongoing operations. Subsurface investigations and review of SDA critical utility drawings indicated that ISG operations would not affect any utilities. The nuclear facility manager and Site Support Services enforced standard precautions associated with springtime subsidence in the SDA through mid-June.

CWI surveyed and marked each ISG site coordinate before HBI mobilized. CWI supplied HBI with coordinates for each of the 2,168 insertion points in EDF-9531 so they could preprogram locations into their positioning system and DAS.

Setup involved establishing operational, RadCon, and OSHA/HAZWOPER boundaries and support facilities at ISG application sites. Boundaries were installed and posted in compliance with the project-specific health and safety plan (PLN-3412) and radiological work permit (No. 31010780). An expansive access-control boundary was established around the perimeter of each work area to encompass the ISG operation. Boundaries normally included more than one ISG site and were posted with signs indentifying the boundary as a “Construction Area,” as a “CERCLA/OSHA HAZWOPER Controlled Area,” and for authorized personnel entry only and included a caution for intermittent high noise. A separate internal boundary was established by safety and IH professionals that encompassed the drill rig, mixing and high-pressure pump facilities, and the entire length of the high-pressure grout supply hose.

Postings consisted of caution “high noise area,” hearing protection required, and danger “high pressure system area.” The geometry of this boundary varied from site to site based on equipment positioning.

Setup also included implementation of the HBI’s ICP-approved O&M Plan (VDR-296417) for managing grout returns and system flush operations. Grout returns basins were developed by excavating the upper 1 ft of overburden, extending nominally 3 ft beyond the outer row of insertion points. Separate basins were excavated in the vicinity of the each ISG site, outside of the designated treatment area, to receive excess grout from the batch plant and pump. Boundaries were posted around these facilities by CWI RadCon, safety, and IH professionals to protect personnel and equipment. A continuous caution boundary was established around the outer perimeter of the grout returns basin. This boundary was posted as a “radiological buffer area” and contained controlled ingress and egress paths, personal protective equipment donning and doffing areas, and a step-off pad for radiation contamination control. RadCon screening tools and supply cabinets were staged just outside the radiological buffer area. The access point was posted as a “CERCLA/HAZWOPER Exclusion Zone.” Located inside of this barrier, nominally following the perimeter of the grout returns basin, was an enclosed caution “Contamination Area” boundary. Figure 37 depicts the relative configuration of the controlled zones with associated postings.

Figure 37. Relative configuration of controlled zones with associated postings.

3.1        Management Self-Assessment and Authorization to Deploy

A hazard assessment document (HAD-460) was prepared to implement a graded approach to nuclear safety management for the project. Waste disposal areas at the RWMC are classified as a Hazard Category 2 nuclear facility. The ISG Project was segmented for hazard categorization from the rest of the RWMC and it was determined to be a less than Hazard Category 3 activity. As such, an MSA was not required but one was performed as a best management practice. This MSA was performed following established procedures for startup of nuclear facilities. An MSA Plan (PLN-3456) was prepared to establish the scope, define the approach and process, and define the prerequisites for the MSA.

The MSA addressed the readiness of personnel, equipment, and work control documents for drilling and grouting operations. The following operational activities were evaluated through observations of evolutions, walkthroughs, interviews, and review of documentation:

• ISG operations, setup, mobilization
• Grout mixing
• Grout delivery
• Drilling
• Grouting
• Cleanup of systems.

HBI began setup of equipment in Cold Test Pit-South on May 10, 2010. The next 2 weeks were devoted to ensuring the equipment met requirements, the operators were fully trained, work control documentation was complete, and practice evolutions were performed for all operations. Figure 38 shows equipment setup in Cold Test Pit-South prior to practice operations.

The MSA started May 24, 2010, and the MSA report was issued June 3, 2010. The MSA evolutions included drilling and grouting two separate locations, equipment clean-out, and removal of the drill mast from the contamination area to simulate equipment relocation. Additionally, a practice fire drill was performed with fire equipment response by the INL Fire Department. Fifty locations were historically mapped for potential use in Cold Test Pit-South, but only six locations were actually used during testing and the MSA. Figure 39 shows the six locations in Cold Test Pit-South that were drilled and grouted. See Appendix A for location coordinates.

Based on successful operational evolutions, HBI was given notice to proceed into the SDA for setup on May 27, 2010. The MSA team identified seven pre-start findings and no post-start findings. Corrective actions were immediately identified and implemented. Work control documents were updated, tailgate training was provided to the operations crew, and ICP authorized HBI to begin operations. Lessons learned from the MSA are provided in Section 6.

3.1        Mobilization

HBI mobilized to the INL Site from May 10 through May 17, 2010. They moved equipment to the Cold Test Pit-South in preparation for the MSA and onsite testing and completed their personnel training. The RWMC nuclear facility manager granted work authorization and Rig #1 was moved onsite. Upon arrival at the INL Site, all HBI equipment underwent baseline surveys by RWMC RadCon personnel (see Section 3.6). The construction STR and the project field team leader oversaw mobilization. Assorted HBI equipment was unloaded from several flatbed trucks using the HBI all-terrain forklift and a leased mobile crane, supported by ICP construction forces with use of an ICP heavy-duty all-terrain forklift (Big Red).

After equipment was unloaded and partially assembled, it was positioned on the Cold Test Pit-South simulated test pit for final assembly. Receipt inspections performed by ICP quality assurance staff identified several nonconformance issues primarily associated with the electrical generator and power feed to the high-pressure pump provided to HBI from a local vendor. ICP construction electricians and RWMC electrical engineering staff contributed to the resolution of these issues by recommending an acceptable configuration. Following installation of the system, a management walkdown of the facilities was performed by the HBI superintendent, the STR, and RWMC safety and quality assurance professionals to ensure operational readiness.

Figure 38. Rig #1 setup in Cold Test Pit-South for the management self-assessment.

In conjunction with equipment mobilization efforts, HBI personnel received pre-scheduled site-specific training through the ICP training organization. Training for workers was tracked on qualified watch lists that were maintained for the project.

In preparation for mobilization into the SDA and hot operations, the project conducted an MSA from May 24 through June 3, 2010 (see Section 3.4). The RWMC nuclear facility manager authorized mobilization to the SDA following successful completion of the MSA.

Figure 39. Six locations in Cold Test Pit-South that were grouted during the management self-assessment.

Rig #1 mobilized into the SDA between May 26 and June 3, 2010, under oversight by the STR and the project field team leader. All HBI equipment was moved into the SDA through the south gate of the RWMC. Mobile equipment was tracked onto the SDA and staged in operational configuration on ISG Site T49A. Support systems were staged using the HBI all-terrain forklift. Following placement, ICP electricians and support staff installed required grounding and oversaw connection of equipment power leads. HBI support trailers previously were staged at the ISG laydown area, and bulk binder materials were placed near the first ISG site, T49A.

At Rig #1, following installation of the system, the HBI superintendent, the STR, and RWMC safety and quality assurance professionals walked down the facilities to ensure operational readiness.

Rig #2 mobilized between June 9 and June 14, 2010, following a similar process. Rig #2 was assembled at Cold Test Pit-South. Required pressure verification testing was performed on June 15, 2010, under RadCon, Safety/IH, quality assurance, project engineering staff, and facility representative oversight. Following verification of operational readiness and authorization by the RWMC nuclear facility manager, HBI Rig #2 mobilized to the SDA via the south gate and was staged over ISG Site T45B.

At Rig #2, following installation of the system supporting Rig #2, the HBI superintendent, the STR, and RWMC safety and quality assurance professionals walked down the facilities to ensure operational readiness.

3.6                  Remedial Action

ISG commenced in the SDA on June 7, 2010, and was completed on August 25, 2010, with a total of 50 days of ISG operations. Treatment is complete at the 21 specified locations, in accordance with the Phase 2 Work Plan (DOE-ID 2010) as implemented through the “Drilling and Grouting Plan for Operable Unit 7-13/14 In Situ Grouting” (VDR-291709).

In accordance with the project specification (SPC-1162), HBI furnished all labor, material, equipment, tools, documentation, and supplies to test and perform the ISG operations using a jet-grouting process with a single-component, cement-based grout. Field operations consisted of site preparation; a design verification phase, including offsite and onsite testing; and a production phase, comprising ISG application, close-out, and demobilization activities. Operations were completed ahead of schedule and under budget with a total of approximately 20,300 man-hours (ICP 14,000; HBI 5,650; and 650 for oversight) and with no first-aid incidents, recordable injuries, lost time accidents, or radiological issues. The production phase began with one jet grout system in operation, with the second system commencing operations on June 18, 2010. In total, 677 tons of cement/slag, yielding 216,165 gal (1,070.3 yd3) of grout was pumped into the subsurface.

Table 8 contains project schedule information and a performance objective summary showing that ISG at each of the 21 locations exceeded 80% of the maximum potential volume, as required. Table 9 contains specific information for each ISG site. The table is organized chronologically by start date.

ISG site information is organized by “Site-Specific Information,” which contains a summary of RadCon and field team leader log information (e.g., routine or anomalous radiological survey data and responses, rig positioning, re-entries into insertion points for grout application); and “Operations and Maintenance,” which highlights impacts to grouting operations (e.g., maintenance activities, weather delays, and operational refinements).

3.6.1             Impacts to Grouting Operations

Based on lessons learned from previous ISG treatability studies, ICP communicated issues inherent to ISG operations to HBI. At the direction of ICP technical project personnel, HBI developed mitigations that were compatible with system hardware and incorporated them into their O&M Plan as “contingencies,” some of which were implemented during the project. The following paragraphs discuss these contingency measures and other mitigations to reduce operational impacts.

3.6.1.1              System Plugging. The most significant impact to ISG operations was the questionable quality of the binder material. Because of the small nozzle size selected for the project it was essential that the binder material be clean and free of impurities. Early in the project, between June 8 and June 17, 2010, HBI experienced mechanical problems with their system as a result of coarse sand discovered in the binder material. To mitigate this problem, HBI returned binder to their supplier and enforced quality assurance procedures for mixing the raw product. In addition, two additional filtration screens (for a total of three) were introduced into the system in advance of the high-pressure pump. The screens prevented impurities in the material from increasing wear on components of the high-pressure pump and prevented plugging the nozzle. Though the screens reduced wear on components of the high-pressure pump, the maintenance required for the pumps was more frequent than originally planned.

Table 8

Table 9

3.6.1.1              Anomalies in Data Sets. Anomalies were observed in the daily jet-grouting reports or DAS curves on the last ISG site, T30, insertion points T30 D006, T30 D012, T30 D018. Both the rpm and pull speed curves reflected fluctuating readings over the duration of the grouting campaign, rendering the curves unreadable. However, raw data indicated that each site was completely grouted within established parameters, as was empirically verified by the observance of grout returns. Based on data analysis and field observations by HBI, the automated grouting system’s response to changing site conditions produced the anomalies.

Automated grouting operations on the HBI drilling systems were controlled by a common proportional integral drive controller control loop feedback mechanism. The controller calculates an error value between a recorded variable in the process and the programmed variable or parameter. Based on the calculations, the loop adjusts the output value for that parameter. With the HBI system, the loop controlled the hydraulic system that operated the revolution speed of the monitor (rpm). This automated adjustment in the rpms occurred within an integral time measured in thousands of a second. For the

subject insertion points, the anomaly observed on the DAS curves was the system continuously correcting itself to maintain a constant rpm rate while being affected by conditions within and external to the grouting hardware, which caused binding on the monitor. Because the integral frequency was so fast, each time an instantaneous correction was made to speed up the rpms to compensate for the binding, another reading was taken before the speed was able to equilibrate, and the system thus decreased the rate to attain the programmed parameter. These opposing adjustments (faster and slower rpm rate swings) were indicated by the anomalous DAS readings, which cycled approximately every 10 seconds. Because these corrections were being made almost instantaneously, raw data indicated that average rpm rates and relative pull speed or retraction rates for the two-step settings used were being maintained within programmed parameters (ranging from 23 rpm and 26 in./minute and 32 rpm and 36 in./minute) for all three insertion points.

Once the problem was observed on the first location, it was corrected by HBI technicians by adjusting the integral time (sampling and adjustment frequency for the loop) during grouting of the subsequent two insertion point locations. Integral times on the second and third locations were increased by 0.015 and 0.020 seconds, respectively. This increase allowed corrections to the rpm speed to be made and the system to equilibrate to the adjustment before another data point was recorded, thus avoiding an opposing correction. Analysis of the problem by HBI personnel indicated that binding on the monitor, which caused the initial problem, may have resulted from changes in friction between the drill string and subsurface, but likely was caused by changes in hydraulic oil temperature and condition or swivel lubrication at the end of the project.

3.6.1.2              Refusal. The Drilling and Grouting Plan (VDR-291709) defined refusal as:

…30 seconds of vigorous drilling with less than 2 inches of penetration. Should penetration attempts utilizing the full range of drilling capabilities slow to a penetration rate of less than six inches in two minutes, this also shall be deemed refusal. Refusal for insertion points immediately adjacent to points having met refusal by this mechanical method, may be determined by judgment of the operator, with the concurrence of the observing STR, provided the vertical difference from the proven refusal depth is less than three feet. Upon reaching the specified depth or refusal, both the driller and ground man will visually confirm that the work area is clear, the driller will contact the pump operator and direct him to bring the pump up to pressure and high pressure grouting shall be initiated.

To simplify operations, HBI adopted the approach to determine refusal at any given insertion point by conducting 30 seconds of vigorous drilling with less than 2 in. of penetration regardless of penetration rates of adjacent points. Drilling was attempted to a total depth of 17 ft bgs for each insertion point located within trench sites and to 25 ft bgs for the soil vault site. Grouting was initiated from the target depth or the point of refusal to 4 ft bgs. Of the insertion points drilled in the 20 trench sites, 3% of the points encountered refusal between 0 and 8.9 ft, 24% of the points encountered refusal from 9 to 14.9 ft, and 73% of the points were drilled to depths between 15–17 ft. In drilling of the soil vault, ISG Site S14, refusal was met at a depth of 14.5 ft on the center location with each of the six perimeter locations being drilled to depths between 21 and 24 ft.

3.6.1.1              Grout Returns Management. Excess grout extruded to the surface via annular space along the drill stem or via previously drilled insertion points, producing grout returns. Returns and associated ground heave from saturated subsurface conditions signify thorough waste zone treatment. Figure 40 shows typical viscous grout returns, observed at the start of grout injection, and pillow-type returns, containing grout mixed with interstitial soil, which occur primarily after starting to retract the drill stem, and an example of ground heave. An optimal ISG operation will produce small volumes of grout returns and little evidence of ground heave, thus reducing the potential spread of contamination, aiding in site restoration, and resulting in a more cost-effective operation. As part of controlling radiological conditions during ISG, a limited exposure criterion was set to prevent overexposing personnel to radiologically contaminated material. Managing grout returns was a critical part of meeting this criterion. Managing returns also was dictated by the project safety basis (HAD-460) and associated basis documents, which assumed no returns from adjacent insertion points. In addition, Phase 2 close-out required that each site be backfilled and restored to existing facility grade and drainage. Control of returns and the degree of associated ground heave within grout returns basins were imperative to preclude disturbing the site (e.g., removing solidified grout returns) to achieve safe and acceptable close-out. Phase 2 grouting parameters were predicated on extensive Idaho National Engineering Laboratory research and development on simulated SDA waste (see Section 3.1 of the Phase 2 Work Plan). Higher densities in actual waste skewed operational parameters (e.g., retraction rates and rpms) toward the upper limit of experimentally derived ranges defined in the Phase 2 Work Plan.

To control the amount of grout returning to the surface, each drill rig was equipped with a dual-speed step function. The dual-speed function allowed the drill rig operator to increase rotations per minute, thus increasing the withdrawal rate. This function was used when the amount of grout returning to the surface was judged excessive by the project engineer or drill rig operator. The drill rig operator increased the rotations per minute at the direction of the STR or from observations of either grout returning to the surface through adjacent holes or ground heave. The drilling pattern was offset in conjunction with the step function. The original pattern was to grout every other insertion point, making primary and secondary passes through each site. Once production began, the project determined further separation between freshly grouted holes was necessary to reduce returns. Every third insertion point in the row was grouted, making primary, secondary, and tertiary passes through each site (Figure 41). Treatment of initial sites required trial and error to optimize this relational approach. Treatment of the first site, T49A, showed ground heave ranging from approximately 8 in. to 18 in. at the center of the site and a range in grout deliveries from 13 gal/ft to 9.5 gal/ft by varying the step function (Figure 42). During grout application on the first three Rig #1 ISG sites, nine insertion points exhibited excessive grout returns and ground heave upon initiation of grout injection because of localized saturation of the waste zone from primary and secondary passes; thus, this grout application was ceased.

Figure 40. Examples of grout returns and ground heave

During the grouting of the third site by Rig #1, T42A, another form of control was identified. Grouting was aborted in locations where grout returns could not be managed by the dual-speed step function. A second entry was attempted in these locations after the surrounding insertions were given time for the grout to set. In total, 12 locations were aborted and re-entered at this site. While implementing these options, the grouting parameters for each drill rig were quickly fine-tuned to optimize the ratio between the amount of grout returning to the surface and the amount of grout being injected into the subsurface. Figure 43 compares sites completed early in the project with those completed later, i.e., following optimization of grouting operations. Over the course of the project, 21 insertion point locations were re-entered for grout application. All but five of these reentries occurred in the first three ISG sites treated.

3.6.1.1              Retraction Rate Exceedance. Daily jet-grouting reports or DAS curves indicated an intermittent exceedance in the established retraction rate of 39 in./minute for specific insertion points associated with ISG Sites T45C, T42B, and T44. In each case, the HBI drill rig operator was conducting grouting operations at the upper allowable rotational setting of 39 rpms in order to control grout returns.

HBI’s automated grouting function was controlled by preprogramming the following three variables: step size, revolutions per step, and monitor rotation or rpms. As the rpms were increased by actuating the step function, so too was the retraction, at a related rate, assuming the other two variables remained fixed. In the case of the subject ISG sites, variability in air temperature, ground conditions, waste forms, and mechanical response caused the step size to drift. The steps increased by up to 1 in., causing the retraction rate to exceed the established parameters even though programming remained within the set parameters. Once this condition was observed, the maximum step setting for monitor rotation (rpms) was decreased from the upper parameter setting of 39 in./minute. This practice continued for the remainder of the project, even though a field change had been implemented to allow operations to exceed the upper retraction rate parameter to manage grout returns (see Section 3.6.2.5). Applying grout at the lower rates increased grout returns, which were closely monitored by RadCon to ensure operational safety.

3.6.2             Operational Refinements

Remedial actions typically involve field decisions. In the context of Phase 2 ISG, field decisions were defined as real-time refinements to ISG site-specific operating parameters. Field decisions were based on a combination of field observations, knowledge of the buried waste (e.g., waste form and container type), and professional judgment. ICP directed HBI to implement field decisions, which were noted in field logbooks. The following sections address these operational refinements. In each instance, DOE, DEQ, and EPA representatives were not present in the field, and the decisions had no impact on the performance goal of 80% of the maximum potential grout volume. Therefore, as the Phase 2 Work Plan (DOE-ID 2010) allowed, when Agency representatives were not present, treatment proceeded without delay, and ICP informed the Agencies of the field change after the fact.

Figure 41. Examples of primary, secondary, and tertiary passes through a site.

Figure 42. Examples of grout returns and ground heave at Site T49A.

Figure 43. Comparison of grout returns and ground heave between sites completed early in the project versus those completed later when grouting operations were optimized.