English

Abstract

Acid mine site remediation is a significant problem, both in the U.S and globally. Due to the volume of acid producing rock the only practical solution is minimizing acid production by reducing or eliminating water flow through the rock. Typically, this is achieved through emplacement of a cap over the waste rock. The Ruby Gulch repository at the Gilt Edge Mine NPL Site is such a capped waste rock repository. Eliminating discharge from valley-fill capped waste-rock repositories is difficult and multiple factors can cause continuing oxidation and ARD discharge. Consequently, early in the cap-cover design EPA and the Bureau of Reclamation design-build team recognized the need for a long-term monitoring system which would provide actionable information on the repository performance and behavior. Specifically, the following objectives were defined for a monitoring system: 1) provide information on the integrity and performance of the newly constructed surface cover and diversion system; 2) continuously assess the waste's hydrological and geochemical behavior, such that rational decisions can be made for the operation of this cover and liner system; 3) provide easy and timely information access on system performance to a variety of stakeholders; and 4) generate information and insights which can be used to enhance future cover and monitoring discussions between EPA, the Bureau of Reclamation and DOE Idaho National Laboratory. A longterm monitoring system was designed and integrated into the multi-layered geomembanerock-soil cap-cover over the 65-acre, 450’-high, sulfide waste-rock dump to provide information to meet these objectives. The system consists of tensiometers, lysimeters and thermocouples in four wells, a 523-electrode resistivity system installed below the cap and in the wells, a weather station, and a precision outflow-meter at the toe-discharge of the repository. Continuous data from this system as well as auxiliary manually collected samples are parsed into a web accessible central server. Automated and on demand data processing allows for 2-D, 3-D and 4-D resistivity tomography and user controllable data mining. The philosophy underlying this system is that it should provide both for effective automated and autonomous data collection and for a cost effective way for multiple stakeholders to use this data. ______________________ 1 Paper presented at the 7 th International Conference on Acid Rock Drainage (ICARD), March 26-30, 2006, St. Louis MO. R.I. Barnhisel (ed.) Published by the American Society of Mining and Reclamation (ASMR), 3134 Montavesta Road, Lexington, KY 40502 2 Ken Wangerud is a Remedial Project Manager in the Superfund Remedial Program at the Environmental Protection Agency, Region 8, Denver, CO 80202. Roelof Versteeg is a Senior Advisory Scientist at the Idaho National Laboratory (INL), Idaho Falls, ID 83415. Gail Heath is a Principal Scientist at the INL, Idaho Falls, Idaho 83415. Rich Markiewicz is a scientist at the Bureau of Reclamation, Denver, CO. Alex Richardson is a scientist at the INL, Idaho Falls, Idaho, 83415. 7 th International Conference on Acid Rock Drainage, 2006 pp 2262-2281 DOI: 10.21000/JASMR06022262