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GOLDER r-- "'""OVED <br /> NP <br /> 2020 <br /> ,ECLAMATION <br /> MIN11'WHNDSAMY TECHNICAL MEMORANDUM <br /> DATE September 4, 2020 Reference No. 20144265-REV1 <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(REVISION 1) <br /> On behalf of Holcim (US) Inc., Golder Associates Inc. (Golder) is submitting this request for a Technical Revision <br /> to 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. This Technical Revision was revised to address DRMS adequacy review <br /> comments. Additionally, the first semi-annual 2020 monitoring results, which were not available at the time of the <br /> initial submittal, have been added to Attachment A and Attachment B. The request from the DRMS was to modify <br /> the groundwater network to 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 Rule 3.1.7(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 /> GOLDER <br />