DERR-2024-012439

Sent via electronic mail
Rob Hartman
Environmental Manager
US Magnesium, LLC
[e-mail]
Re: Agency acceptance and finalization of Baseline Ecological Risk Assessment Report, Baseline
Human Health Risk Assessment, and Remedial Investigation Path Forward,
Administrative Settlement Agreement and Order on Consent for Remedial
Investigation/Feasibility Study (Docket No. CERCLA-08-2011-0013)
US Magnesium Superfund Site, Tooele County, Utah
Dear Mr. Hartman:
The U.S. Environmental Protection Agency has completed its review of the Operable Unit 1 (OU1)
Baseline Ecological Risk Assessment Report (BERA Report), submitted October 17, 2024, pursuant to
the Administrative Settlement Agreement and Order on Consent for Remedial Investigation/Feasibility
Study (Docket No. CERCLA-08-2011-0013) (AOC) for the US Magnesium Superfund site (Site).
The EPA hereby approves the OU1 BERA Report, as submitted October 17, 2024. This report fulfills the
requirements of Section 5.3.1.4 and Section 5.3.1.5 of the Statement of Work (SOW), for OU1. The
OU1 Baseline Human Health Risk Assessment (HHRA), submitted to the EPA on April 29, 2022, has also
been approved by the EPA and fulfilled the requirements, for OU1, of Section 5.3.2.1 and Section
5.3.2.2 of the SOW. The final, EPA-approved versions of both the OU1 BERA Report and HHRA are
enclosed with this correspondence.
The next deliverable listed in the SOW is the Draft Remedial Investigation (RI) Report. Due to
unanticipated and/or changed circumstances at the Site, including the stop in construction of the
slurry/barrier wall (i.e. CERCLA Response Action), termination of magnesium and lithium production,
and the subsequent reduction of air emissions from the US Magnesium (USM) facility, USM shall
proceed with an RI Report for only the unsaturated zone soils at this time. Pursuant to the SOW
(Section 5.4 of the AOC), the draft RI Report will be due within 200 days of confirmation of the
determination that no further field work is necessary. If further field work is necessary, the EPA
requests that USM submit, within 14 days, a timeline for completion of any further field work
necessary for an RI Report for unsaturated zone soils. Alternatively, if no further field work is
necessary, USM shall begin developing a Draft RI Report (for unsaturated zone soils) to be submitted
within 200 days.

The EPA requests that USM provide confirmation of willingness and intention to proceed with the
proposed path forward within seven days of receipt of this EPA request.
If you have any questions or concerns, please contact me at [e-mail].
Sincerely,

Tabetha Lynch
Remedial Project Manager

Enclosures:
Final OU1 BERA Report
Final OU1 HHRA

cc:
Andrew Schmidt, EPA
Matt Hogue, EPA
Wes Sandlin, UDEQ
Kelsey Robinson, UDEQ