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ARCADIS <br />tnlratitt,a tut;. Wato 1 nott mnuvtt li(,rhilnc), <br />Mr. Justin Andrews <br />Environmental Manager <br />Holcim (US) Inc. <br />3500 Highway 120 <br />Florence, Colorado 81226 <br />Subject <br />MW -7 Redevelopment and Semi - Annual Groundwater Monitoring Summary for <br />Holcim (US) Inc. Portland Plant Quarry <br />Dear Mr. Andrews: <br />This letter report summarizes the redevelopment and semi - annual groundwater <br />monitoring of MW -7 associated with the disposal of cement kiln dust (CKD) into <br />previously mined areas of the Portland quarry. <br />Per the requirements of the Colorado Division of Reclamation Mining and Safety <br />(DRMS) MW -7 compliance standards, if the results of two or more of the selected <br />analytes used for compliance [total dissolved solids (TDS), sulfate, potassium, <br />sodium, iron, and manganese] exceed their respective compliance values by more <br />than 10 percent, then Holcim is required to modify the sampling frequency from <br />annual to semi - annual in this well. In March 2012, annual groundwater sampling <br />results for MW -7 indicated that iron and sodium concentrations exceeded the DRMS <br />compliance standards by more than 10 percent; therefore, an additional sampling <br />campaign was scheduled for September 2012. <br />Due to slow recharge observed in MW -7 during previous annual sampling events, <br />ARCADIS recommended that this well be redeveloped prior to sampling in <br />September 2012. <br />MW -7 Redevelopment <br />MW -7 was redeveloped on September 14, 2012 approximately 2 weeks prior to the <br />semi - annual sampling on September 28, 2012. <br />Use or disclosure of information contained on this sheet is subject to the restriction and disclaimer located on <br />the signature page of this document <br />C 1Users1Iyusko \Documents \Holam12012 MN -7 Redevelop ISummary Letter12012 1217 Holcim Portland Well Dev Sampling Summary Letter doc <br />ARCADIS <br />10559 Citation Drive <br />Suite 100 <br />Brighton <br />Michigan 48116 <br />Tel 810.229 8594 <br />Fax 810 229 8837 <br />www.arcadis - us.com <br />Environment <br />Date <br />December 17, 2012 <br />Contact <br />Chris Peters <br />Phone <br />810.225.1905 <br />Email <br />Chris.peters@arcadis- <br />us.com <br />Our ref <br />80025510.0012 <br />Page. <br />1/5 <br />