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LOPage 2 Mr. Eric Scott <br /> G U,,, September 18, 2019 CO DRMS <br /> • To develop optimal groundwater elevation data(if observed) while meeting the <br /> safety infrastructure protection criteria discussed above. The groundwater data can <br /> be incorporated into mine planning, groundwater impact evaluations, and <br /> groundwater modeling [Monitoring]. <br /> MONITORING NVELL DESIGN <br /> The proposed MW's will initially extend to a bottom elevation (El.) of 6400 <br /> (approximately 200 feet below existing grade depending on final location and site grading <br /> at time of installation). These MW's will be utilized to monitor the presence and <br /> conditions of groundwater within South Quarry during initial phases of South and West <br /> Quarry mining. Once mining is scheduled to proceed below El. 6465 (in approximately 10 <br /> years), AI will deepen the wells or relocate and install additional wells, as necessary, to the <br /> appropriate bottom El. This will be completed in coordination with the DRMS. <br /> As shown in Figure 3, the MW's will be constructed with 1-inch diameter schedule 80 <br /> PVC in HQ boreholes (3.78-inch outside diameter). The MW's will include an 18-inch <br /> surface stickup and extend to an approximate El. of 6564 including a 12-inch sand trap. <br /> Each well will have a 20-foot screened section and will be backfilled with 10-20 sand to 12 <br /> inches(minimum) above the screened section. The annulus will then be sealed with a <br /> cement-bentonite mixture followed by a bentonite plug. Surface completion will consist of <br /> concrete extending a minimum of 12 inches into the borehole annulus and the construction <br /> of a 6-inch thick well pad extending 2 feet beyond the edge of the borehole. The MW's <br /> design and construction will meet the Colorado Division of Water Resources(DWR) <br /> requirements for monitoring well construction(2 CCR 402-2). The MW's will be <br /> permitted with the DWR pursuant to 37-92-602, C.R.S. <br /> MONITORING PLAN <br /> These proposed wells are tentatively scheduled to be installed in early October 2019 and <br /> only a draft monitoring plan has been developed at the time of this TR. A final monitoring <br /> plan will be presented in the forthcoming resubmittal of the M-1973-021 AM-06. As no <br /> groundwater contamination is anticipated, the monitoring plan will not include sampling <br /> and analysis for groundwater quality. <br /> Please contact me at 970-224-7343 if you have any comments or questions. <br /> Sincerely, <br /> GEI CONSULTANTS, Inc. <br /> eremy Deuto, P.E., P.G. An rew Lockman, P.G. <br /> Project Manager Senior Reviewer <br /> CC: Jeremy Pritchett,Lafarge <br />