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Sheldon Mine

 
Site Contact:
Dan Shane
On-Scene Coordinator

(shane.dan@epa.gov)

Site Location:
3850 Eagle Road
Walker, AZ 86303
 response.epa.gov/SheldonMineSite

The Sheldon Mine Site is located within un-incorporated areas of the Bradshaw Ranger District of the Prescott National Forest. The Site consists of two waste areas. The Sheldon Waste Rock (SWR) pile is approximately 3.5 acres and consists of between 40,000 and 80,000 cubic yards of waste rock situated immediately adjacent to a tributary stream to Lynx Creek. The Sheldon Tailings Pile (STP) is approximately 3.2 acres and consists of about 10,000 cubic yards of tailings located about 200 feet from Lynx Creek. Mining activities occurred between the 1860's and 1950's. Mine operations recovered gold, silver, copper, lead and zinc. This removal action will be addressing the STP area. The SWR area will be addressed in a separate removal action in the future.

In 1975, the Forest Service and Univ of Arizona conducted a reclamation project to re-contour, cover and re-vegetate both SWR and STP. The re-vegetation in large areas failed and erosion has washed away the soil cover exposing the tailings. Surface drainage systems that diverted water away from the piles are choked with sediment. Storm water flows onto the site and infiltrates into the tailings pile producing AMD which is evidenced by orange colored liquid emanating from the toe of the pile and discharging to a stream that flows to Lynx Creek. In 2005 and 2012, soil, water and sediment sampling conducted by EPA revealed high levels of arsenic and lead. This discharge impacted the water quality in Lynx Creek and Lynx Lake. There were homes and children living near the site. The primary threats to human health were exposure to arsenic and lead from breathing dust, drinking contaminated water and children playing in the soil and water in the creek.

The proposed removal action will isolate and cover the existing tailings pile to prevent direct human contact and off-site migration of contaminants. The actions will involve excavating contaminated sediments out of the stream and incorporating the material into the pile, regrading the surface of the pile to promote proper drainage, install a french drain system around the perimeter of the site, and construct an evapotranspiration cover consisting of layers of wood chip mulch, clean soil, biosolids and finally hydroseeded with native plant species.

The removal action will begin on April 15, 2013 and will take 6 weeks to complete.


View of excavation area in drainage below the tailings pile. Two to three feet of contaminated sediment was removed. Walker Historic Marker View of operations from top of the tailings pile facing south Excavator removing contaminated sediment in drainage below tailings pile View of EPA Command Post View of drainage below tailings pile EPA Command Post 21,000 gal Frac Tank used to store reclaimed water for dust control. View of Lynx Creek below the tailings pile Soil borrow area known as Gates Tank Dam on U.S. Forest Service lands located 8 miles from the site. Excavator at toe of tailings slope building earthen ramp out from the driveway. Construction of earthen ramp to the top of the tailings pile Setting up office trailer View of tailings pile facing north ERRS Crew hydrates concrete cloth. ERRS Crew installs 18 Close up of concrete cloth. ERRS Crew begins installing concrete cloth in French drain on east side of tailings pile. Eastern French drain during construction Trench for north perimeter French drain. First load of biosolids delivered Northwest end of drainpipe Finished concrete lined French drain along northern perimeter of tailings pile, facing east. Another east facing view of finished French drain along north side of tailings pile. Finished French drain, facing west. Concrete lined basin in the northeast corner on top of tailings pile. Northern perimeter and eastern perimeter drainpipes are shown. Completed concrete lined French drain along eastern perimeter of tailings pile ERRS crew installs concrete cloth in spillway V-ditch. Another view of concrete cloth in spillway and V-ditch View of ERRS crew installing concrete cloth in V-ditch. Close up view of concrete cloth. Joining perforated piping w/ coupler. Riprap delivered to site, light (8 Class A biosolids. Transition from french drain to trapezoidal channel. Spreading mulch at upper tailings pile. Spreading mulch on upper tailings area. Transition from french drain to trapezoidal channel. Compacted topsoil on east end of upper tailings pile First lift of cap around trees. Upper tailings pile. East end of upper tailings pile. Light compaction of second lift on east end of upper TP. Straw errosion control fiber rolls (wattles). East end of upper tailings pile transition to the french drain. Stilling Basin SB-3, riprap set. Hand placement still pending. Upper tailings pile, topsoil extended down slope Biosolids stockpiled on the upper tailings pile. Placing topsoil on slope. French drain, dressed up. Placing topsoil on far side of french drain. Preparing the basin above Eagle Road. Disking in the biosolids on the upper tailing pile. Disking in the biosolids in the upper tailings pile. SB-5, Eagle Road SB-5, concrete cloth tucked under culvert. Bottom gabion in SB-1. Straw errosion control fiber rolls (wattles) at top of TP. Stilling Basin SB-5 above Eagle Road with boulders on concrete cloth for energy dissipation. Remaining armouring to be performed. Gabions around the 12 Continued armouring in SB-1. Stilling Basin SB-3 rocked. Biosolids (dark material) spread on surrounding soil, not yet tilled into topsol. Stormwater erosion control in SB-6. V-channel with concrete cloth. SB-5 with riprap. Breaking rock in Walker road in preparation for culvert Hydrating concrete cloth in SB-1. Breaking rock in Walker Road Spreading mulch on lower tailings pile. Spreading mulch on slope, wattles being placed. Wattles on slope. Staking wattles. Tree trunks placed around tree wells. Tree trunks placed around tree wells, soil raked up against tree. Tree trunks placed around tree wells, soil raked up against tree. Dumping rock adjacent to SB-6. Placing rock in SB-1. Rock placed in SB-6. Rock placed in SB-6. Grading the lo.wer tailings pile Placing riprap in the trapezoidal channel. Preparing trench on north side of Eagle Road. Cleaning up riprap placed in trapezoidal channel by the excavator. View of toe of tailings pile and fencing subcontrators installing barbed wire fence Workers in trench installing 36 View of nearly restored soil borrow area on USFS lands. Approximately 4,390 cubic yards of material was used for the vegetative cover.