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• 1.0 INTRODUCTION <br />At the request of Cripple Creek & Victor Gold Mining Company (CC&V), Shepherd Miller, [nc. <br />(SMI) investigated [he cause of the recent zinc concentrations in the flows from the Carlton <br />Tunnel. Monitoring of the Carlton Tunnel water by CC&V showed higher than usual <br />concentrations of potentially dissolved zinc during spring and summer of 1999. This report <br />summarizes the current and historic precipitation rate for Southern Teller County and the <br />relationship between precipitation and flow rates and zinc concentration from the Carlton <br />Tunnel. An evaluation of these data then allows the quantities of flow and potential sources of <br />zinc in the Cazlton Tunnel flow to be interpreted. The data presented supports the conclusion <br />that an "upset" condition occurred at the Carlton Tunnel as a result of the extremely heavy <br />precipitation received in Southem Teller County since April 1999. <br />An "upset" condition is defined by the Colorado Department of Public Health and Environment <br />as (p. 10 of 19, Part [I.A.2 (d) of Colorado Discharge Permit System No. CO-0024562): "An <br />exceptional incident in which there is unintentional and temporary noncompliance with permit <br />• effluent limitations because of factors beyond the reasonable control of the permittee. An upset <br />does not include noncompliance to the extent caused by operational error, improperly designed <br />treatment facilities, inadequate treatment facilities, lack of preventative maintenance, or careless <br />or improper operation." <br />This report concludes that the elevated zinc concentrations in the flows from the Carlton Tunnel <br />during spring and summer of 1999 represent an "upset" condition that resulted from unusually <br />heavy precipitation. The heavy precipitation produced some of the highest flows from the <br />Carlton Tunnel recorded in the last 10 years and caused a rinsing of zinc from the hydrologic <br />system. The upset condition is supported by an evaluation of: (1) local and regional precipitation <br />data, (2) flow rates at the Carlton Tunnel, (3) zinc concentration data at the Carlton Tunnel, (4) <br />age dating of the water at the Carlton Tunnel, and (5) data presented in previous investigations. <br /> <br />Cripple Cmek & Vicmr Gold Ninmg Compnny S(upherd Efifler, Inr. <br />IIDlAAIONO~P~OR/VEll~J6TRrrynUenrlnrnJ Aa 1 Navembrr ll. 1999 <br />