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ARCADIS <br /> !n(rastruc turn Lba!Y !rrormnrrmrrt Baxlr;rnc;.+ <br /> ARCADIS <br /> 1687 Cole Blvd. <br /> Suite 200 <br /> Lakewood <br /> Colorado 80401 <br /> Mr. Timothy A. Cazier, P.E. Tel 303.231.9115 <br /> Environmental Protection Specialist Fax 303.231.9571 <br /> Colorado Division of Reclamation, Mining and Safety www.arcadis-us.com <br /> Department of Natural Resources <br /> 1313 Sherman Street, Room 215 <br /> Denver, Colorado 80203 <br /> Environment <br /> Subject: <br /> Response to DRMS Technical Revision(TR-10) Preliminary Adequacy Review <br /> Holcim (US) Inc. Portland, Colorado Limestone Quarry, Permit No. M-1977-344 <br /> Date: <br /> November 19, 2014 <br /> Dear Mr. Cazier: <br /> Contact: <br /> ARCADIS has prepared this letter on behalf of Holcim (US) Inc. (Holcim) to respond Chris Peters <br /> to the Division of Reclamation, Mining and Safety (DRMS) Technical Revision (TR- <br /> 10) Technical Adequacy Review of the "Proposal to Remove Sodium as a Phone: <br /> Groundwater Quality Parameter — DRMS Permit No. M-1977-344, Technical 517.324.5052 <br /> Revision No. 6", dated August 4, 2014 and received by DRMS on October 20, 2014. Email: <br /> The DRMS responded to the above proposal in a letter to Justin Andrews of Holcim chris.peters@ <br /> dated October 31, 2014, requesting additional information be provided before they arcadis-us.com <br /> would authorize the removal of sodium as a water quality parameter to evaluate <br /> potential impact from leaching of cement kiln dust(CKD). our ref: <br /> B0025510 <br /> Presented below is a summary of the DRMS comment from the October 31 letter <br /> followed by ARCADIS' response. We believe this information will provide the <br /> justification to remove the numeric protection level (NPL) for sodium from the <br /> groundwater monitoring program, approved by the DRMS on February 24, 2009 and <br /> updated on November 27, 2012. We would propose as a revision to the groundwater <br /> monitoring program to continue to analyze groundwater samples for sodium in order <br /> to continue to determine the potassium to sodium ratio, which we would propose to <br /> replace the sodium NPL as the primary water quality indicator of impact from the <br /> CKD landfill. <br /> 1) Relationship between depth to water and sodium concentration in <br /> monitoring well MW-7: <br /> The DRMS acknowledges that the higher concentrations of sodium observed in MW- <br /> 7 may be partially attributable to lower water levels in that monitoring well, but <br /> commented that ARCADIS should provide further discussion as to why the <br /> increased sodium concentrations are not attributable to impacts from CKD. <br /> Imagine the result <br />