Idaho Maryland Mine - Rise Grass Valley

Project Contact: Senior Planner, Matt Kelley


This is an application for a proposed Conditional Use Permit and Reclamation Plan for the Idaho Maryland Mine, owned by Rise Grass Valley, a private company. The County’s role will be to process and review the application for consideration by the Nevada County Planning Commission and Board of Supervisors in accordance with the requirements of the County General Plan, Land Use and Development Code, California Environmental Quality Act and other appropriate state and federal laws. As part of the review process, there will be opportunities for the public to provide comments on the proposed project. These opportunities will include upcoming noticed Public Scoping Meetings as part of the environmental review process, noticed Public Hearings and on the draft and final environmental documents. Please sign up using the link below to receive these notifications as well as other project updates and information.

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The project is a combined application for a Conditional Use Permit and Reclamation Plan to reinitiate underground mining and gold mineralization processing of the Idaho-Maryland Mine within unincorporated Western Nevada County. The proposed project would be located on two properties owned by Rise Grass Valley, which are referred to as the Brunswick Industrial Site (APN’s: 009-630-037 - 21.8 Acres, 009-630-039 – 15.07 Acres, 006-441-003 – 15.19 Acres, 006-441-004 – 0.85 Acres, 006-441-005 – 50.01 Acres, 006-441-034 – 16.01 Acres) and the Centennial Industrial Site (APN’s: 009-550-032 – 0.48 Acres, 009-550-037 – 4.47 Acres, 009-550-038 – 40.1 Acres, 009-550-039 – 0.98 Acres, 009-550-040 – 0.13 Acres, 009-560-036 – 10.25 Acres). As proposed the project would include the following elements:

  • Dewatering of the existing underground mine workings.
  • Mining existing and new underground mine workings.
  • Processing gold mineralization and rock.
  • Placing engineered fill at the Brunswick and Centennial Industrial Sites
  • Export of engineered fill from the Brunswick Industrial Site to support local construction projects.

As proposed, the Use Permit and Reclamation Plan would include the following uses and facilities:

  • Operation of pumps and a water treatment facility to dewater the underground mine workings.
  • Construction of a water pipeline to transport treated water to an outfall located in South Fork Wolf Creek.
  • Construction of the necessary aboveground facilities at the Brunswick Industrial Site (to include but not limited to, headframes and hoists, surface structures, a mineral processing plant) to support underground mining and mineral processing.
  • Underground mining, including drilling, blasting, and gold mineralization removal.
  • Gold mineralization and rock processing at the Brunswick Industrial Site and off-site transport of gold concentrate.
  • Transport of engineered fill from the Brunswick Industrial Site and placement at the Centennial Industrial Site.
  • Transport of engineered fill from the Brunswick Industrial Site to off-site construction projects.
  • Placement of engineered fill at the Brunswick Industrial Site.
  • Construction of a potable water pipeline to supply residences along a portion of East Bennet Road.

As proposed, the project would be comprised of approximately 175 total surface acres and approximately 2,585 subsurface acres to which the applicant retains the mineral rights. In addition to the above uses and facilities, the proposed project would also include a Rezone application to rezone the parcels located at the Brunswick Industrial Site from Light Industrial (M1) with Site Performance Combining District (SP) to Light Industrial (M1) with Mineral Extraction Combining District (M1-ME) to allow for surface mining operations on the surface, pursuant to Nevada County Land Use and Development Code, Section L-II 2.7.3. The project would also include a Reclamation Plan and required Financial Assurance Cost Mechanisms to reclaim the project site to a condition suitable for industrial uses as allowed by the LUDC, Section L-II 2.5 – Industrial Uses and Table L-II 2.5.D – Light Industrial. In addition, the project includes a request for a Variance to the Building Height Limits to allow for the construction of several structures up to a height of 165 feet, where 45 feet is required, pursuant to the Light Industrial Zoning District. Lastly, the proposed project includes a Management Plan component to allow for development within the required 100-foot setback of the Riparian Area of Perennial Watercourse, pursuant to LUDC, Section L-II 4.3.17 and to minimize the direct impact to special-status plant species, pursuant to LUDC, Section L-II 4.3.12.

As part of the application, the Nevada County Planning Department has received several Technical Reports including:

  • Noise and Vibration Analysis Idaho - Maryland Mine.
  • Environmental Factors of Blasting Report for the proposed Idaho-Maryland Mine Gold Project.
  • Geotechnical Engineering Report – Idaho-Maryland Mine Project, Brunswick Industrial Site.
  • Preliminary Drainage Analysis & Detention Basin Sizing for Centennial & Brunswick Sites.
  • Cultural Resources Survey Report for the Idaho-Maryland Mine Project.
  • Idaho Maryland Water Treatment Plant Design,
  • Biological Inventory Reports & Management Plans.

Additional Technical Reports are in progress by the applicant and will be made available upon receipt, including:

  • Aesthetics Analysis.
  • Cultural Impact Report.
  • Air Quality and Greenhouse Gas Analysis.
  • Traffic Analysis.
  • Land Use Technical Study
  • Groundwater Hydrology and Water Quality Analysis.
  • Groundwater Model Report.
  • Paste Backfill Geochemistry.
  • Geomorphology Analysis Report.
  • Geotechnical Report for the Centennial Industrial Site.