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STATE OF COLORADO <br /> DIVISION OF RECLAMATION,MINING AND SAFETY <br /> Department of Natural Resources <br /> 1313 Sherman St.,Room 215 C O L O RA D O <br /> Denver,Colorado 80203 A S V I S I O N o f <br /> Phone:(303)866-3567 RECLAMATION <br /> FAX:(303)832-8106 MINING <br /> SAFETY <br /> November 27, 2012 John W.Hickenlooper <br /> Governor <br /> Mike King <br /> Executive Director <br /> Joe Lamanna Loretta E.Pineda <br /> Holcim (US),Inc. Director <br /> 3500 Highway 120 <br /> Florence,CO 81226 <br /> Re: Portland Limestone Quarry, Permit No. M-1977-344, Revised Groundwater <br /> Monitoring Plan <br /> Mr. Lamanna: <br /> The Division of Reclamation, Mining and Safety (DRMS) has reviewed your proposed standards <br /> for MW-13 (reference Holcim letter to DRMS dated July 7, 2010). The data collected from MW-13 <br /> is intended to supplement data collected from MW-7. The DRMS approved numeric protection <br /> levels (NPLs)for MW-7 on February 24,2009. <br /> The DRMS determines NPLs based on the five quarters of monitoring data initially collected from a <br /> proposed monitoring well, not from nearby or upgradient wells. The selected NPL is typically the <br /> larger of two values: 110 percent of the maximum concentration of a constituent of interest <br /> observed during the five quarters of monitoring; or the mean observed concentration of the <br /> constituent plus two standard deviations. Based on the five quarters of data provided by Holcim for <br /> MW-13,the DRMS has determined the following NPLs are appropriate: <br /> Parameter NPL for MW-13 Previously Approved NPL for MW-7 <br /> Total Dissolved Solids(TDS) 4,026 mg/f * 3,918 mg/f <br /> Sulfate(SO4) 2,200 mg/f * 2,080 mg/E <br /> Potassium(K) 13 mg/f *$ 17 mg/f <br /> Sodium(Na) 274 mg/f * 226 mg/L <br /> Iron(Fe—dissolved) 0.13 mg/f $ 4.5 mg/f <br /> Manganese(Mn-dissolved 0.30 mg/f $ 0.88 mg/f <br /> * 110%of maximum observed value <br /> $Mean observed value plus 2 standard deviations <br /> Holcim will continue to monitor MW-12 (background) and MW-7 (west compliance well), and <br /> provide results for the above parameters on an annual basis. When observed parameters in MW-7 <br /> and/or MW-13 (east compliance well) exceed the NPL by more than 10 percent, Holcim will <br /> increase the monitoring frequency to semi-annually. <br /> Office of Office of <br /> Mined Land Reclamation Denver•Grand Junction•Durango Active and Inactive Mines <br />