Laserfiche WebLink
Reclamation Feasibility Report - Virginia Canyon <br />Water Quality Impacts <br />• The principal water quality effect from this site is probably from leaching of the mine waste. The <br />collapsed adit drains perennially onto the waste rock, infiltrates the waste rock, and emits as a series <br />of springs below the county road. In addition, the waste rock pile completely blocks Boomerang <br />Gulch. During small runoff events, all the flow in Boomerang Gulch infiltrates the pile and emits as <br />springs below the road. During larger events, some of the flow passes through a channel on the <br />northwest side of the pile, while some flows over the pile, eroding the face. <br />All the flow sampled at water quality station VC-18 during May of 2000 can be attributed to the mine <br />drainage. The water quality at station VC-18 generally had significantly higher heavy metal <br />concentrations than the mine drainage at station DM-3. During the thunderstorm in August of 2000, <br />virtually all the flow was passing over the waste rock pile. <br />The waste rock had the second highest concentrations of soluble cadmium and zinc of the 79 sites <br />sampled. It is thought that the metals concentrations inside the pile will be significantly less than <br />found on the surface. Leaching by the perennial mine drainage appears to precipitate metals on the <br />top and outslope of the waste rock pile. The common flow path for the mine drainage is coated with <br />secondary metal sulfides and sulfate salts. This portion of the waste rock was not sampled. Results <br />from the 2:1 leachate analysis are given below: <br /> <br />• <br /> <br />PH <br />S.U. OIL= V4,0 <br />Total Acidity <br />m /I <br />As <br />b <br />Cd <br />b <br />Cu <br />b <br />Fe <br />b <br />Mn <br />b <br />Pb <br />b <br />000 <br />Zn <br />b <br />140000 <br />2.59 1700 1500 840 12000 190000 1800 65 <br />26 <br /> Site It <br />Pb <br />Zn <br />PH <br />S.U. Total Acidity <br />m /I As <br />b Cd <br />b Cu <br />b Fe <br />b Mn <br />b b <br />0 b <br />18000 <br />2.66 660 220 110 2700 89000 240 1300 <br />Reclamation Measures <br />The recommended reclamation measure for this site is partial removal, with in-situ cementation of <br />the remainder of the pile. The loadout structure is supported by the waste rock pile. Because of the <br />historic nature of this structure, that portion holding up the loadout must remain. The eastern side of <br />the pile can be removed to allow free flow down Boomerang Gulch. Although the waste rock at site <br />#26 does exhibit better chemical characteristics than the main pile, this material would also have to <br />be removed or partially removed to construct a stream channel around the remaining portion of the <br />pile. As an alternative, an engineered concrete channel can be constructed over the pile. If this <br />option is chosen, the ground water flow path must be cut off by constructing a grout curtain. <br />The mine drainage from the collapsed adit can be partially treated using a sulfate reducing wetland. <br />The pH of the mine drainage is favorable, but the iron and aluminum content may be high enough to <br />shorten the life of the treatment system. This can be partially offset by constructing an anoxic <br />limestone drain and small settling pond in the collapsed adit. However, the aluminum in the <br />drainage may result in a plugged drain. There should be sufficient area near the collapsed adit to <br />construct a small passive treatment system. <br />Foxhall Tunnel (Site #28) <br />Location <br />This site is located in Seaton Gulch approximately 1/2 mile above the confluence with Virginia <br />• Canyon (Figures 3 and 14). The mine site is visible from the upper road in Virginia Canyon between <br />34