Idaho-Maryland Mine Project

2 Documents in Project


SCH Number
Lead Agency
Nevada County
Document Title
Idaho-Maryland Mine Project
Document Type
EIR - Draft EIR
Present Land Use
The proposed project’s surface components would be located on approximately 175.64 acres consisting of the Brunswick Industrial Site, the Centennial Industrial Site, and a 0.30-acre portion of East Bennett Road for off-site improvements associated with a potable water pipeline easement. The project sites contain the historic Idaho-Maryland Mine underground gold mine. The condition of the Centennial Industrial Site is a combination of past industrial use and undeveloped land with natural habitats. The Centennial Industrial Site includes densely vegetated areas interspersed with past disturbance from historical mining at the site, including industrial structures and wood and metal materials left by the previous owner of the site. A separate Centennial Clean-Up Project is currently being processed for the Centennial Industrial Site by the Department of Toxic Substances Control (DTSC).
Document Description
The proposed project would reinitiate underground mining and gold mineralization processing for the Idaho-Maryland Mine over an 80-year permit period with gold mineralization processing and underground exploration and mining proposed to operate 24 hours a day, 7 days a week during full operations. Following completion of mining and processing activities, the project sites would be reclaimed to open space and land suitable for future development of industrial uses. Generally, the proposed project would include the following components: • Dewatering the existing underground mine workings; • Underground mining at a depth of 500 feet or more in areas underlying the mineral rights properties; • Construction and operation of aboveground processing and water treatment facilities at the Brunswick Industrial Site; • Engineered fill placement for potential future industrial pad development at the Centennial and the Brunswick Industrial Sites; • Installation of a potable water pipeline for residential potable water supply; and • Reclamation of the project sites in accordance with a proposed Reclamation Plan. The majority of the aboveground facilities, access to the underground mining, and a portion of the engineered fill would be located on the Brunswick Industrial Site. The aboveground facilities would be located within a 29-acre industrial area that would include but not be limited to, a headframe building around the existing concrete silo used to hoist rock from the Brunswick shaft; covered conveyor system used to transport a) barren rock to a truck hauling area within an adjacent enclosed building, and b) gold concentrate to the processing plant; a processing plant to grind rock and recover gold minerals through various processes; and other appurtenant structures such as office and warehouse space. An above-ground water treatment plant would also be built at the Brunswick Industrial Site to treat groundwater associated within initial and ongoing (“maintenance”) dewatering of the underground mine workings. A new aboveground pipe would convey treated water from the water treatment plant along an existing dirt road to the planned discharge point at South Fork Wolf Creek. The pipe and discharge point are located entirely within the property boundaries. Engineered fill generated by the proposed mining activities would be placed on approximately 31 acres of the Brunswick Industrial Site to create a level pad of approximately 21 acres for potential future industrial use. In total, up to approximately 60 acres of the 119-acre site could be subject to surface disturbance and/or development for the aboveground facilities and fill placement. The remaining 59 acres would remain undeveloped and would not be subject to surface disturbance or infrastructure improvements. Engineered fill would also be placed on the Centennial Industrial Site, provided that the separate DTSC cleanup project has been approved and completed on the Centennial Industrial Site. In that case, engineered fill would be transported by truck from the Brunswick Industrial Site and placed on approximately 44 acres of the Centennial Industrial Site to create approximately 37 acres for potential future industrial use. The remaining approximately 12 acres would remain as a private driveway for site access and open space. The open space area would include Wolf Creek, a 100-foot setback for riparian area on Wolf Creek, and an undisturbed area providing protection for identified special-status plant species. After full placement of fill at the Centennial and Brunswick Industrial Sites to the pad design elevations, the need for hauling of engineered fill would continue due to ongoing mining over the Use Permit term of 80 years, and thus, hauling would shift entirely to local and regional markets for sale as construction aggregate and fill. If the separate DTSC cleanup project is not approved by DTSC and completed within the term of the Idaho Maryland Mine Project use permit, engineered fill would be placed on the Brunswick site, but not the Centennial site, and the remainder would be hauled to local and regional markets. A buried potable water pipeline would be constructed as part of the proposed project to provide water to residences along a portion of East Bennett Road. The pipeline would extend an existing Nevada Irrigation District (NID) potable water pipeline along an approximately 1.25-mile segment of East Bennett Road to provide potable water service to residential properties currently on wells that may be affected by the project’s dewatering of the mine. NID would be the water supplier for the potable water service.

Contact Information

Matt Kelley
Agency Name
Nevada County Planning Department
Job Title
Senior Planner
Contact Types
Lead/Public Agency


Cross Streets
Idaho Maryland Rd., Brunswick Rd., E. Bennett Rd., Whispering Pines Ln.
Total Acres
Parcel #
State Highways
20, 49, 174
Nevada County Airport
Wolf Creek, South Fork Wolf Creek

Notice of Completion

State Review Period Start
State Review Period End
State Reviewing Agencies
California Air Resources Board (ARB), California Department of Conservation (DOC), California Department of Forestry and Fire Protection (CAL FIRE), California Department of Parks and Recreation, California Department of Resources Recycling and Recovery, California Department of Transportation, District 3 (DOT), California Department of Transportation, Division of Aeronautics (DOT), California Department of Transportation, Division of Transportation Planning (DOT), California Department of Water Resources (DWR), California Energy Commission, California Governor's Office of Emergency Services (OES), California Native American Heritage Commission (NAHC), California Natural Resources Agency, Central Valley Flood Protection Board, Office of Historic Preservation, Sierra Nevada Conservancy, State Water Resources Control Board, Division of Drinking Water, State Water Resources Control Board, Division of Drinking Water, District 9, State Water Resources Control Board, Division of Water Rights, State Water Resources Control Board, Divison of Financial Assistance, California Highway Patrol (CHP), California Regional Water Quality Control Board, Central Valley Sacramento Region 5 (RWQCB), Department of Toxic Substances Control, California Department of Fish and Wildlife, North Central Region 2 (CDFW)
State Reviewing Agency Comments
California Highway Patrol (CHP), California Regional Water Quality Control Board, Central Valley Sacramento Region 5 (RWQCB), Department of Toxic Substances Control, California Department of Fish and Wildlife, North Central Region 2 (CDFW)
Development Types
Industrial (Sq. Ft. 1, Acres 104, Employees 1), Water Facilities (Pipeline)(Type Pipeline, MGD 1), Mining (Mineral Gold)
Local Actions
Rezone, Use Permit
Project Issues
Aesthetics, Air Quality, Biological Resources, Cultural Resources, Cumulative Effects, Drainage/Absorption, Flood Plain/Flooding, Geology/Soils, Greenhouse Gas Emissions, Hazards & Hazardous Materials, Hydrology/Water Quality, Noise, Septic System, Transportation, Tribal Cultural Resources, Vegetation, Wetland/Riparian, Wildfire


Notice of Completion [NOC] Transmittal form

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