1992-05-29_REVISION - M1988112 (3)

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1 1 J PROPOSED MODIFICATIONS TO THE GROUND WATER MONITORING PLAN, SAN LUIS GOLD PROJECT, COSTILLA COUNTY, COLORADO INTRODUCTION The current approved ground water monitoring in the vicinity of the tailings facility and collection pond includes monitoring wells M-6, M-7, M-8 and M-9, installed at varying depths. Well M-6 was completed to a depth of 30 feet, well M-7 was completed to a depth of 45 feet, well M-8 was completed to a depth of 133 feet and well M-9 was completed to ~ depth of 210 feet. This monitoring plan was approved as part of the amended permit application and Battle Mountain has been operating this baseline data collection program for approximately three years. However, in response to observed higher-than-expected cyanide concentrations in the tailings facility, the CMLRB issued a Notice of Probable Violation to Battle Mountain on March 31, 1992. As part of that Notice of Probable Violation, CMLRD issued an Abatement Plan on April 24, 1992, which included, among other items, a directive to Battle Mountain to "te-evaluate its approved program for ground water monitoring, sampling and analysis for the tailings disposal area" (Item 6 of the Abatement Plan document). This report presents Battle Mountain's proposal to install additional ground water monitoring points in the vicinity of the tailings facility and collection pond. These proposed monitoring points will evaluate the magnitude and direction of gromid water flow, evaluate aquifer Hydraulic characteristics so that control of the local ground water gradient can be achieved by pumping, and serve as permanent ground water quality monitoring points. Protocols rel8ted to actual sample collection, handling and laboratory analysis from ground water wells were previously transmitted to you in a document entitled "Quality Assurance/Quality Control Protocols for the