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GOLDER <br /> TECHNICAL MEMORANDUM <br /> ' DATE July 24, 2020 Project No. 20144265 <br /> TO Amy Eschberger <br /> ' Colorado Division of Reclamation, Mining and Safety <br /> CC Mike Toelle and Travis Bennet(Holcim (US) Inc.) <br /> ' FROM Sara Harkins and Joanna Moreno EMAIL sharkins@golder.com <br /> REQUEST FOR TECHNICAL REVISION (TR-11) OF PERMIT M-1977-348: CHANGES TO THE <br /> ' GROUNDWATER MONITORING NETWORK AT THE BOETTCHER QUARRY <br /> On behalf of Holcim (US) Inc., Golder Associates Inc. (Golder) is submitting this request for a technical revision to <br /> ' permit M-1977-348 to modify the groundwater monitoring program for the Boettcher Limestone Quarry (Site) <br /> located at 3060 West County Road 56, Laporte, Colorado 80535. <br /> This technical revision was requested by the Division of Reclamation, Mining, and Safety (DRMS) in their <br /> ' February 28, 2020 Inspection Report. The request from the DRMS was to modify the groundwater network to <br /> include two additional monitoring wells, a background well, and a compliance well. <br /> ' 'By the corrective action date, the operator shall submit a Technical Revision, with the applicable fee, to revise the <br /> groundwater monitoring program to include proposed point(s) of compliance in accordance with Rule 3.1.7(6) and <br /> (7) at some distance hydrologically downgradient from the Cement Kiln Dust(CKD) disposal areas. Due to the lack <br /> of ambient groundwater quality data for the site required by Rule3.1.7(b)(viii), the revision shall also include <br /> ' proposed background monitoring well(s) located outside of the CKD disposal areas and screened across similar <br /> lithological units as existing downgradient monitoring wells and the proposed compliance well(s). The information <br /> obtained from these wells will be used to evaluate protection afforded groundwater quality and compliance with <br /> groundwater standards." <br /> Upon further conversations with the DRMS it was determined the background well will be installed and monitored, <br /> ' whereas the downgradient compliance well will be installed at a later date, if needed. This technical revision <br /> details: <br /> ■ Proposed locations <br /> ' ■ Drilling and well installation specification <br /> ' ■ Monitoring and evaluation criteria <br /> ■ Reporting <br /> ' 1.0 PROPOSED LOCATIONS <br /> The proposed locations for both wells are shown in Figure 1. The locations are approximate and may be shifted <br /> slightly (less than 50 feet) prior to drilling. The locations were selected to be are also near current access roads on <br /> ' the Site and will allow access using a truck mounted drill rig. <br /> ' GOLDER 1 <br />