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NPDES Compliance and Remedial Design

Stowell Mine
Shasta County, California
 
VESTRA serves as the environmental and engineering consultant for the owner of the Stowell Mine Complex in Shasta County, California. The objectives of the ongoing activities are to eliminate ARD from the Stowell Complex and restore a fishery in Spring Creek. Historically, dissolved copper, cadmium, and zinc from the Stowell Complex discharged to Spring Creek, a fish-bearing stream. Spring Creek enters the Sacramento River below Shasta Dam. The Stowell Complex consists of three main portals and two waste rock piles.  Between 2001 and 2009, VESTRA staff completed the permitting, design, and construction inspection of the following remedial activities at the Stowell Complex. These activities were conducted pursuant to NPDES Permit and Cease and Desist Order and included: 
 
  • Excavation and consolidation of approximately 36,000 cubic yards of waste rock located on a steep slope immediately above Spring Creek. Because of our experience in water quality issues and the regulatory environment, staff members were retained to provide professional engineering, environmental, and geotechnical services to assist in the fast-track design and permitting of a Title 27 waste rock containment facility sited in steep mountainous terrain west of Lake Shasta. The waste rock was relocated to an HDPE-lined containment cell.
  • Installation of a bulkhead seal in the Davis portal. The Davis portal was uncovered during the waste rock removal project. A bulkhead seal was designed and installed in October 2003. 
  • Injection of compost behind the Upper and Lower Stowell portals to stimulate SRB activity. The compost was injected through the bulkhead seals, and through boreholes drilled into the tunnels behind the bulkhead seals. 
  • Construction of a quarter-acre passive sulfate-reducing system to treat residual ARD from three sealed portals and the installation of a leach field to receive treated effluent from the systems. The treatment unit was completed in 2009.
  •  Installation of continuous monitoring stations in Spring Creek to verify the success of the remedial activities.
Following the completion of these activities, point source discharge from the Stowell Complex to Spring Creek has been eliminated. As a result, the Stowell Mine will be removed from the NPDES program and future discharges to land will be regulated through the Waste Discharge Program.