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HOWARD FORK ACID ROCK DRAINAGE SOURCE INTERCEPTION STUDY; HOWARD FORK OF THE SAN MIGUEL RIVER NEAR OPHIR, COLORADO
Impact/Purpose:
Across the west, acid rock drainage (ARD) is a significant point source contributor of heavy metals and pollution, severely degrading water quality and aquatic habitat, impairing aquatic life and making water virtually unusable. The Howard Fork of the San Miguel River, in San Miguel County, Colorado, like many other rivers and streams in the west, has been impacted and degraded by mining, most of which occurred between 1880 and 1950. Today, draining adits are among those remnants of historical mining activity that continue to discharge water contaminated by metals loading and acid rock drainage directly or indirectly into the river. Tailing piles and waste rock dumps, many located directly adjacent to the Howard Fork, represent a significant source of metals loading. Generally, tailing and waste rock problems enjoy relatively straightforward remedies that fall under CERCLA legislation. Along the Howard Fork, landowners, the local community, and several government agencies, including the US Forest Service, the Colorado Department of Public Health and Environment, the Colorado Division of Minerals and Geology, the USGS and the US EPA are cooperating to develop remediation plans for tailing piles and waste rock dumps. There remains a profound need to develop, on the Howard Fork and elsewhere, cost-effective strategies to reduce acid rock drainage which are of interest to landowners not wishing to take on additional liability under the provisions of the Clean Water Act.
Description:
This project proposes to analyze regional hydrogeology as it relates to mine workings which discharge significant heavy metals into the Howard Fork of the San Miguel River and recommend strategies to intercept and divert water away from mineralized zones. The study also includes elements critical to understanding the associated environmental liability issues; land use review, landowner and public outreach, and regulatory law and liability analysis. To evaluate the potential of incepting groundwater prior to entering the mine workings, we propose the following activities as part of a scope of work. 1) Land use, land ownership analysis and landowner outreach. 2) Literature search. Water quality, geologic, mine working maps and other mining related information specific to the Howard Fork will be collected, reviewed and evaluated. 3) Quality assurance planning. 4) Database development. Working with the CGS and the CDPHE, a water quality database will be developed. New data collected during this study, including geo-chemical and adit flow discharge data will be entered into the database and made available to interested parties. 5) Development of a project specific GIS platform. This information will include location of sampling points, the geology of the basin, location of mine workings, aerial photographs, and other geographic information available. Locations of mine adits and sampling locations will be identified using GPS. 6) Water quality sampling. Sampling will take in consideration of the work done by CGS and CDPHE. Samples will be taken and analyzed for field parameters and select trace metals. GPS will locate adits, wells, springs, and sampling locations for the GIS database. 7) Geologic mapping and lineament study. Concurrent with the well and spring survey, existing geologic maps will be verified and a lineament study will be completed using aerial photographs. 8) Continuous flow monitoring. Installing meters and taking flows from draining adits on a continuous basis will enable evaluation of hydrographs to determine how discharge corresponds to snow melt and other precipitation events, giving some indication of how mine workings might be connected to the surface through fractures. 9) Development of conceptual hydro-geologic model. Based on geologic mapping, spring survey, mine maps, flow data and water quality data, a conceptual hydro-geologic model will be developed for the basin. This model will allow us to select one or two sites to develop pilot remedial water interception plans, as further described below. 10) Pilot remediation design. Based on results of conceptual modeling described above, one or two mines will be selected to be further studied in detail. The study will involve the development of a three dimensional model of the mine workings, underground mapping if possible, a detail review of mine history, and a detail write-up of the hydro-geology of the mine. With this information, a remediation design with preliminary costs will be produced. 11) Environmental liability analysis. Analysis of the laws and regulatory framework that impact any phase of the study or the proposed remediation will be considered. 12) Remediation funding opportunity analysis. 13) Public outreach. 14) Quarterly reports and final report to EPA.