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1 ARCADIS <br /> ARCADIS <br /> 1687 Cole Blvd. <br /> Suite 200 <br /> ' Lakewood <br /> Colorado 80401 <br /> Mr.Timothy A. Cazier, P.E. TeI303.231.9115 <br /> Environmental Protection Specialist Fax 303.231 9571 <br /> Colorado Division of Mining Reclamation and Safety www.arcadis•ws.com <br /> Department of Natural Resources <br /> 1313 Sherman Street, Room 215 <br /> ' Denver, Colorado 80203 <br /> Environment <br /> Subject: <br /> Holcim(US)Inc. Portland, Colorado <br /> Proposal to Remove Sodium as a Groundwater Quality Parameter <br /> DRMS Permit No. M-1977-344,Technical Revision No. 6 Date: <br /> 1 August 4,2014 <br /> Dear Mr. Cazier: <br /> Contact <br /> ARCADIS has prepared this letter on behalf of Holcim (US) Inc. (Holcim) to propose Chris Peters <br /> 1 that sodium be removed as groundwater quality indicator parameter for the <br /> groundwater monitoring program from the above referenced Phone <br /> g g p g permit. We have 517.324.5052 <br /> provided Site and literature data to show that sodium concentrations are not a useful <br /> indicator of groundwater impacts from leaching of cement kiln dust(CKD),which has Email. <br /> been disposed at the Holcim Portland Quarry landfill (Figure 1)throughout the life of chris.peters@arcadis- <br /> the permit. us.Com <br /> ' The requirement for using sodium as an indicator parameter in groundwater Our ref <br /> monitoring is based on Division of Mining Reclamation and Safety (DRMS) letters B0025510 <br /> from February 24, 2009 and November 27, 2012 to Holcim, setting the numeric <br /> protection limits(NPLs) for monitoring wells MW-7 and MW-13, respectively. These <br /> letters are included in Attachment 1 to this letter. <br /> Sodium concentrations in monitoring well MW-7 have increased over time as shown <br /> on Table 1 and Figure 2, and continue to exceed the sodium NPL for that well. <br /> Based on the latest sampling event (March 2014), the sodium concentrations <br /> exceeds the NPL by approximately 12% (253 vs. 226 mg/L). We believe that the <br /> increases in sodium concentration are unrelated to releases from the CKD landfill,as <br /> discussed below. <br /> ' On-Site Data <br /> Monitoring well MW-7 was installed in 1998 and has been sampled periodically since <br /> that time. As shown on Table 1 and illustrated on Figure 2, there is a strong <br /> correlation between groundwater elevation (represented as depth to water) and <br /> sodium concentration. Depth to water (DTW) in MW-7 has increased since 1998. <br /> ' Imagine the result <br /> i <br /> I <br />