DSHW-2024-005847

April 16, 2024
Lonnie Brown
Chief, Environmental Division
1 Tooele Army Depot
JMTE-BON, Bldg. 501
Tooele, UT 84074-5003
RE:Water Supply Well WIN 9549EPA ID #UT3213820894
Dear Mr. Brown:
During the April 10, 2024, monthly update call for Tooele Army Depot (TEAD) projects, Tyson Erickson brought up concerns about use of groundwater from an off-site extraction well located
within the Solid Waste Management Unit (SWMU) 58 groundwater plume. Mr. Erickson indicated the well was being used for dust suppression, washing gravel, and a restroom. The well appears
to be owned and used by the Kilgore Company.
Module IX.A.2of the TEAD – North (TEADN) Part B Permit (Permit) indicates thatthe Permittee shall conduct corrective measures in accordance with the Corrective Measure Implementation
Plans (CMIPs) (revisions dated 2010, 2012, 2014) and references four primary elements to ensure the protection of human health and the environment. Condition IX.A.2.a specifically refers
to the implementation of the Updated Groundwater Management Area (GWMA) Plan (2022) and Institutional Controls to prevent current and future human and ecological exposure to contaminated
groundwater.
Condition IX.M.1 further states that the Permittee shall assure that monitoring and corrective action measures necessary to achieve compliance with the groundwater protection standards
are taken during the term of the Permit.
The 2005 SWMU 58 Risk Assumptions document and the 2008 Human Risk Assessment in the Phase II Resource Conservation and Recovery Act (RCRA) Facility Investigation indicated that the
only significant potential exposure pathways for groundwater was ingestion by future residents and ingestion by future industrial worker. Inhalation of contaminants volatilized from
groundwater into outdoor or indoor air and inhalation of contaminants from impacted groundwater used for industrial processes, among others, were assessed and determined to be incomplete
or insignificant.
However, new information concerning use of the production well (well identification number (WIN) 9549) located within the boundary of the trichloroethene (TCE) groundwater plume at a
gravel mining pit (Kilgore), negates the previous conclusion that the industrial use pathway is incomplete. The GWMA Plan states that the well is used for non-potable water supply for
restrooms and other general uses associated with the gravel pit operations (e.g., dust control and gravel washing). However, dermal contact, incidental ingestion, and inhalation of TCE
vapors is likely. The GWMA Plan as well as the GWMA map provided in Appendix IX-A of the Permit show the location of the well within the plume boundary that exceeds the TCE Maximum Contaminant
Level (MCL).
Given the length of time that has elapsed since the 2005 and 2008 risk analyses, and the knowledge that the Well WIN 9549 is located within the known boundary of the SWMU 58 TCE plume,
the Division requests that the risks associated with groundwater being accessed and used at this well are re-evaluated to determine what steps may be necessary to ensure on-going protection
of human and ecological exposure to the contaminated groundwater. The risk-re-evaluation should be conducted using current groundwater data from the well to include a site-specific
exposure scenario(s). Please submit to the Division within 60 days a workplan outlining the steps that will be taken to complete this evaluation of exposure risk.
If you have any questions, please call Jasin Olsen at [phone].
Sincerely,
Douglas J. Hansen, Director
Division of Waste Management and Radiation Control
DJH/JO/wa
c:Jeff Coombs, Health Officer, Tooele County Health Department
Bryan Slade, Environmental Health Director, Tooele County Health DepartmentTyson Erickson, Environmental Protection Specialist, TEADN ([e-mail])Annette Maxwell,
USEPA, Region 8 ([e-mail])Tara Hubner, USEPA, Region 8 ([e-mail])