Argonaut Mine Tailings Feasibility Study/Remedial Action Workplan

Argonaut Mine Tailings Feasibility Study/Remedial Action Workplan

The Department of Toxic Substances Control (DTSC), pursuant to authority granted under Chapter 6.8, Division 20, section 25300 et seq approved a Argonaut Mine Tailings Feasibilty Study/Remedial Action Workplan which proposes conveyance improvements for stormwater management immediately downstream of the Argonaut Dam. The project site is located in the City of Jackson at the intersection of Argonaut Drive and Sutter Street. The project would convey stormwater to Jackson Creek following the retrofit design of the Eastwood Concrete Multiple Arch (CMA) Dam located on the Argonaut Mine Site in Jackson, California. The Concrete Multiple Arch Dam, also known as the Argonaut Dam, was built in 1916 and stands 46 feet in height and spans over 400 feet in length. Argonaut Dam was constructed as part of a historical gold mining operation and has impounded arsenic-contaminated mine tailings as a result of sediment runoff from more than 50 acres of private land in the city of Jackson. The project aims to provide conveyance of stormwater to Jackson Creek. The proposed RAP would involve the following specific improvements to be implemented to the existing drainage system: - Replace inlet structure to provide additional capacity near Vogan Toll Road and Sutter Street (existing open channel terminates at a 27-inch culvert); - Construct a 36-inch pipeline, which will be trenched under Sutter Street, to the fifth manhole; - Construct a 42-inch pipeline, which will be trenched under Sutter Street, from the fifth manhole to the westside of Highway 49/88; - Extend the 42-inch pipeline underneath Highway 49/88, by using a jack and bore technique to minimize disruption of existing public facilities; - Extend the 42-inch pipeline to an existing 10 by 10-foot culvert box that discharges into Jackson Creek using open trenching. Removal of the existing stormwater infrastructure would also be required as part of the proposed project. The existing stormwater infrastructure would be hauled to and consolidated behind the Argonaut Dam at an area designated as Tailings Area 3 which the U.S. Environmental Protection Agency (EPA) has indicated will be a repository for hazardous materials that will ultimately be capped. Activities associated with the Feasibility Study/Remedial Action Plan would occur over an approximately 3-month period.

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