The Yerington Mine Site is located approximately two miles west of Yerington, directly off of Highway 95, at 103 Burch Drive, Yerington, Lyon County, Nevada, and includes portions of Township 13N, Range 25E, Sections 4, 5, 8, 9, 16, 17, 20, and 21 (Mount Diablo Baseline and Meridian) on the Mason Valley and Yerington USGS 7.5 minute quadrangles. The geographic coordinates are 38 59' 53.06" North latitude and 119 11' 57.46" West longitude. The Site occupies 3,468.50 acres of disturbed land in a rural area, bordered to the north by open fields of alfalfa and residential acreage, and to the east by Highway 95, which separates the Site from the city of Yerington. Approximately fifty percent of the Site is privately owned land, and the rest is land within the jurisdiction, custody and control of the United State Bureau of Land Management (“BLM”).
The Site began operation in or about 1918, originally known as the Empire Nevada Mine. In 1953, Anaconda Minerals Company (“Anaconda”) acquired and began operating the Site. In or about 1977, Atlantic Richfield Company (“Atlantic Richfield”) acquired Anaconda and assumed its operations at the Site. In June 1978, Atlantic Richfield terminated operations at the Site. In or about 1982, Atlantic Richfield sold its interests in the private lands within the Site to Don Tibbals, a local resident, who subsequently sold his interests with the exception of the Weed Heights community to Arimetco, Inc. (“Arimetco”), the current owner. Arimetco operated a copper recovery operation from existing ore heaps within the Site from 1989 to November 1999. Arimetco has terminated operations at the Site and is currently managed under the protection of the United States Bankruptcy Court in Tucson, Arizona.
EPA conducted an initial removal action at the Site, from February to May 2006. This work focused on removal of PCB containing transformers and fugitive dust suppression including construction of an 80-acre soil cap and application of a soil sealant to other areas of the site believed to be contributing dust.
From August to November 2006, EPA condcuted a second removal action which addressed fluids management problems associated with the Arimetco Heap Leach System. This system includes ten ponds, all of which are in varying stages of disrepair. As part of this removal action, EPA conducted repairs and improvements to the Slot Pond #2, constructed an interceptor trench along the Megapond and constructed a four-acre Evaporation Pond.
In August and November 2007, EPA ERS conducted two additional removal assessments at the Site. One assessment focused on evaluating radiological contamination of the “Process Area” of the Site. The second removal assessment performed in August 2007 consisted of sub-surface sampling and analysis beneath the Arimetco heap leach ponds.
From October to November 2007, EPA conducted a removal action to address fluids management issues associated with the Bathtub Pond. This removal action included removal of sediments and liner from the pond, backfilling and grading the pond and construction of an interceptor trench along the shoulder of the pond.
9/29/2008-10/04/2008. Personnel: EPA-4, ERRS-12, Northwest Linings-3
During this period ERRS continued to make excellent progress towards closure of heap leach ponds. Activities conducted included the following:
Raffinate Vaults. Two subsurface, concrete vaults (approximately 20 feet long, 10 feet wide and 6 feet deep were identified just west of the Old Raffinate Pond. It was determined that these vaults were full of liquid and sludge. Liquid and sludge from these vaults was taken to the biormediation pad on top of the slot heap. The concrete walls and floors of the vaults were removed and placed in the onsite construction debris landfill. Kerosene contaminated soils adjacent to and below the vaults were excavated and placed in the bioremediation pad. Approximately 800 cubic yards of contaminated soil was removed from the vault area, whereas 9,000 cubic yards of contaminated soil was previously removed from the Old Raffinate Pond and placed in the bioremediation pad. Confirmation sampling will be conducted on 10/6 in the vault area excavation, but it is likely that not all kerosene contamination has been removed. The OSC will document the area of excavation via GPS coordinates.
Old Raffinate Pond. ERRS resumed backfilling of this pond on 10/3.
MegaPond. ERRS completed excavation of the MegaPond on 10/3. This was a substantial effort, as the Megapond is more than 800 feet long. Sediment from the Megapond was placed in a cell on top of the adjacent heap. Material from the berm that ran along the east side of the Megapond was used to partially backfill the Megapond.
Perimeter Ditches. ERRS continued to conduct repairs/upgrades to the Phase I/II and Slot perimeter ditches. These repairs/upgrades consist of repairing torn liner, placing gravel and perforated pipe in the perimeter ditches, covering the gravel with filter fabric, and then covering the fabric with material from the heap.
The Northwest Lining crew arrived onsite 10/3. They spent 10/3 and 10/4 patching perimeter ditch liner and prepping for installation of the liner in the Phase I/II pond, which will begin on 10/6.
The goal of this removal action is to complete stabilization of the Arimetco Heap Leach Fluids Management System. The following activities will be performed:
Slot Pond #1. Contaminated sediments will be removed from this pond and placed on top of the adjacent Heap Leach Pad. The liner will be removed from the pond and placed in the onsite construction debris landfill
Plant Feed Pond. Contaminated sediments will be removed from this pond and placed on top of the adjacent Heap Leach Pad. The liner will be removed from the pond and placed in the onsite construction debris landfill. The area of the pond will be regraded,
New Raffinate Pond. Contaminated sediments will be removed from this pond and placed on top of the adjacent Heap Leach Pad. The liner will be removed from the pond and placed in the on-Site construction debris landfill. The area of the pond will be regraded,
Old Raffinate Pond. Contaminated sediments will be removed from this pond and placed on top of the adjacent Heap Leach Pad. The liner will be removed from the pond and placed in the onsite construction debris landfill. Kerosene-contaminated soils have been identified beneath this pond. The kerosene-contaminated soils will be excavated and either treated onsite or shipped offsite to an appropriate disposal facility.
Phase I/II Pond. Contaminated sediments will be removed from this pond and adjacent sediment pond and placed on top of the adjacent Heap Leach Pad. The liner will be removed from the Phase I/II pond and sediment pond and placed in the onsite construction debris landfill. The Phase I/II Pond and the adjacent sediment pond will be reconstructed, in order to continue to capture heap leach fluids. These fluids will be transferred to the Evaporation Pond via an existing pipeline.
Megapond. Contaminated sediments will be removed from this pond and placed on top of the adjacent Heap Leach Pad. The liner will be removed from the pond and placed in the on-Site construction debris landfill. The area of the pond may be regraded, at the discretion of the OSC.
VLT pond. This pond still captures heap leach fluids from the VLT heap. The liner is sagging in numerous areas, and small tears have been identified. This liner will be repaired.
Perimeter drains. Numerous tears have been identified in the perimeter drains which encircle the heap leach pads. To the extent practicable, the torn areas of the drains will be repaired and steps will be taken to limit future sun and wind damage to the perimeter drain liners, including covering damage portions of the perimeter drains with crushed gravel.
Ecological Mitigation. USFWS has identified several dead birds in the vicinity of the heap leach ponds. USFWS attributes the bird mortality to the low pH fluids in these ponds. Closure of the above-mentioned ponds should help to limit the threat to wildlife posed by the heap leach ponds. EPA will evaluate, and to the extent practicable, implement measures at the remaining heap leach and evaporation ponds aimed at deterring birds from accessing these ponds.
Line Phase I/II Pond.
Complete backfilling of Old Raffinate Pond.
Initiate repairs to VLT pond.
Continue repairs/upgrades to the perimeter ditches.
Begin hauling and mixing amendments for biormediation pad.
ERRS is quickly approaching their project ceiling of $1 million. The OSC has requested that the EPA Remedial program fund the additional $200,000 remaining in the ERRS Action Memo ceiling budget via the ARC special account. The EPA Remedial Program has indicated that they intend to provide the additional funding.
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