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US EPA Iron King Mine & Humboldt Smelter Superfund Site (TPD1209032)


Iron King Mine & Humboldt Smelter Superfund Site

U. S .  E n v i r o n m e n t a l  P r o t e c t i o n  A g e n c y   |  R e g i o n 9   |  S a n F r a n c i s c o , C A  |  S e p t e m b e r  2 0 1 2

Interim Removal Report Available Online

Site Update

Removal Report Available Online

EPA completed a removal action in November 2011. The in- terim removal action began in September 2011, and included the cleanup of residential yards, the removal of the Small Tailings Pile, and the application of a soil sealant to ash piles at the Humboldt Smelter.


As part of this removal action, EPA remediated 11 yards, replaced up to two feet of soils with clean backfill, and re- stored them to their original condition. These yards contained elevated levels of arsenic and lead. The soils removed from the yards were placed on the Main Tailings Pile at the Iron King Mine. Hydro-seed was added on top of the soils to encourage vegetation growth and act as a temporary dust suppressant.


Te Small Tailings Pile, located adjacent to the Chaparral Gulch was also relocated as part of the removal action. Over 20,000 cubic yards were removed and placed in a designated storage area on top of the Iron King Main Tailings Pile. Upon placement of the Small Tailings Pile in the storage area, Gorilla-Snot®, a temporary soil sealant was applied to this area to act as a temporary dust suppressant. After the Small Tail-ings Pile was removed from its original location, the area was restored to a natural drainage pathway.


A severe monsoon in July 2012 damaged certain soil cleanup areas that were remediated during the removal action. EPA   is currently evaluating these properties to be repaired and re-graded.

The final report documenting the removal action is available in the information repository at the Dewey-Humboldt Town Library, located at 2735 S. Corral Street, Dewey-Humboldt, Arizona. It can also be found online at http://www.epa.gov/region09/ironkingmine.


Update on Field Investigation Efforts

Iron King Mine Stability Sampling

In January 2012, additional data was collected to evaluate the stability of the Iron King Mine Main Tailings Pile. Cone pen- etration technology (CPT) was used to evaluate the strength  of the tailings at approximately 40 locations. Preliminary re- sults indicate the volume of the tailings pile is approximately

3.2 million cubic yards (instead of the original estimate of

6.4 million cubic yards). Geotechnical samples were collected from four additional locations in May 2012 to further char- acterize the tailings. The results and analysis of these sampling events will be included in the Remedial Investigation (RI) Addendum.

Soil Sampling

EPA is currently evaluating the levels of naturally occurring metals in the area. In January and April 2012, X-ray Floures- ence (XRF) samples were collected to continue this evalua- tion. Laboratory samples were also collected in January 2012, May 2012, and June 2012. Samples were collected throughout the Dewey-Humboldt area, encompassing approximately 20 square miles (5 miles east to west and 4 miles north to south).

The XRF and soil data are currently being analyzed to evalu- ate background at the Site. Once the soil data has completed validation, results will be provided to the residents whose properties were sampled. The results and analysis of these sampling events will be included in the RI Addendum.




Figure 1. The Superfund Process for the Iron King Mine – Humboldt Smelter Superfund Site


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Groundwater Well Installation

EPA has completed the installation of four additional groundwater wells at the Iron King Mine Tailings Pile. EPA is also in the process of installing two wells down-gradient of the Mine. The instal- lation of these additional groundwater wells will provide more information on the arsenic levels in the groundwater at and down-gradient of the Iron King Mine Main Tailings Pile.


Due to several technical issues encoun- tered in the field during installation, the installation of the down-gradient wells has been delayed. Groundwater sampling of the newly installed wells, in addition to the existing EPA wells, is scheduled to take place in October 2012. The results and analysis of these sampling events will be included in the RI Addendum.


Cleanup Schedule Update

Due to complications with the field in- vestigation, the overall cleanup schedule has been delayed. The Remedial Investi- gation Addendum, which will summa- rize and analyze all field data collected after March 2010 in addition to existing data, is anticipated to be completed in Summer 2013. EPA will then complete  a Feasibility Study (FS) Report, which will evaluate cleanup options for the Site.

The next step following the completion of the RI/FS is the Proposed Plan. The Proposed Plan does the following:

  • briefly summarizes the RI/FS
  • presents a comparison of all the considered alternatives
  • presents the EPA’s Preferred Alter- native – the method that EPA is proposing to clean up the Site
  • explains the reasons why EPA is proposing the Preferred Alternative, as compared to the other alterna- tives evaluated in the FS


During this phase of the Superfund process, EPA will solicit public com- ment on the Proposed Plan, including  all of the alternatives considered in the FS. EPA will consider all comments from the public and support agencies. EPA will then document its final deci- sion regarding the selected remedy in a Record of Decision. EPA will prepare a responsiveness summary explaining how public comments have been addressed. Currently the Proposed Plan is sched- uled to be issued to the public in 2014.

Project Manager Updates

Wayne Miller has replaced Wendy Flood as the Arizona Department of Environmental Quality (ADEQ) Project Manager working on the Site. Wendy Flood is now the ADEQ Community Involvement Coordinator.


Signage, Fencing and Additional Information

EPA has worked with the property owners to ensure their properties have signs and are fenced to the extent prac- ticable. However, if trespassers are seen on the smelter property or community members would like to report suspicious or criminal activity, contact the Yavapai County Sheriff’s Department at (928) 771-3260 or call 9-1-1 in case of emergency.


If you encounter an open mine shaft located outside of the Iron King Mine or the Humboldt Smelter, please contact the Arizona State Mine Inspector at (602) 542- 5971. For more information, visit their website at http://www.asmi.state.az.us/faq.asp.

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Mailing List Coupon

If you are not already on EPA’s mailing list for the Iron King Mine – Humboldt Smelter Superfund Site, please send an e-mail or return the coupon below to David Cooper.

Name                                                                                                     Mailing Address                      City, State                                                             Zip                            Telephone  (optional)                                                                                            E-mail (optional)                  Affiliation (optional)                                                                                                                  





September 2012                                                                                                                                                                                                      3


Iron King Mine & Humboldt Smelter Superfund Site



Contact Information

If you have questions or concerns, please contact any of the following individuals:


Information Repository

For site documents, please visit the


EPA Contacts

Jeff Dhont Remedial Project Manager




David Cooper Community Involvement Coordinator

(415) 972-3245

toll free (800) 231-3075




Monika O’Sullivan Remedial Project Manager

(415) 972-3111



ADEQ Contacts

Wayne Miller

ADEQ Project Manager Federal Projects Unit (602) 771-4121



Wendy Flood Community Involvement Lead

Remedial Projects Section (602) 771-4410



information repository at:

Dewey-Humboldt Town Library

2735 S. Corral Street Dewey-Humboldt, AZ


Please visit EPA’s and ADEQ’s Iron King Mine and Humboldt

Smelter site websites at:



http://www.azdeq.gov/environ/ waste/sps/statesites.html#ironking



U.S. EPA Permit No. G-35


United States Environmental Protection Agency, Region 9 75 Hawthorne Street (SFD-6-3)

San Francisco, CA  94105 Attn: David Cooper (IKHS 9/12)



Official Business

Penalty for Private Use, $300 Address Service Requested

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