The Inyo National Forest is closing the Mammoth Stamp Mill Site due to elevated levels of metals that were determined to pose a risk to human health and the environment. Antimony, arsenic, lead, and mercury were identified as the primary chemicals of concern.
U.S. Forest Service completed a Preliminary Assessment/Site Inspection (PA/SI) at the Mammoth Stamp Mill Site last year to evaluate whether historic mining activity impacted the surrounding environment. The agency initiated the PA/SI under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) in response to the results of initial investigations (2012–2014), which indicated metals were present in site soil at elevated concentrations.
The PA/SI determined that further action is necessary to address risks from exposure to metals at the site. The U.S. Forest Service will implement a Time-Critical Removal Action (TCRA) under CERCLA to address the threats posed to human health. The risks were determined to be moderate to high for human health risk (based on the location and use type). The TCRA will involve removal and disposal of all metals-impacted waste and soil that may pose a risk to human health at the site.
Clean-up at the site is anticipated to begin as soon as the snow melts sufficiently to allow site access by heavy equipment (estimated to be mid-June 2017). The U.S. Forest Service is negotiating with the Potentially Responsible Party (PRP) to implement the clean-up action. A forest order is closing the area and the trail to the public; including recreation residences (who have a cabin under a special use permit). For more information, please consult the PA/SI, the Mammoth Stamp Mill Fact Sheet, the Mammoth Stamp Mill Frequently Asked Questions, the Technical Memo and the Forest Order.
A public meeting is scheduled for May 15th from 5:00 pm to 7:00 pm at the Auditorium at the Mammoth Lakes Welcome Center to share and discuss the findings and to talk through concerns and questions.
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