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BRIERLEY <br /> ASSOCIATES <br /> Creating Space underground <br /> October 14, 2019 <br /> Aggregate Industries-WCR, Inc. <br /> 1687 Cole Boulevard, Suite 300 <br /> Golden, CO 80401 <br /> Attention: Andre Laroche <br /> Environment and Land Manager <br /> Subject: Daniels Sand Pit 2, Permit M-1973-007-SG; <br /> Response to"Approval Succession of Operators, Revision SO-2, with Stipulations" <br /> Mr. Laroche, <br /> In response to Attachment A of the August 26t', 2019"Approval Succession of Operators, <br /> Revision SO-2,with Stipulations" letter by Timothy Cazier, Brierley Associates is providing this <br /> technical revision support. This letter addresses the Fountain Mutual irrigation ditch(lined and <br /> unlined)on the west and east side of S Academy Blvd. and four cross sections on the adjacent <br /> roads Cassidy St., Bradley Road, and Milton E. Proby Pkwy in Colorado Springs, CO. Figure 1 <br /> presents the requested cross sections locations. <br /> Regarding the DRMS stipulations: <br /> A. A signed structural agreement for the Fountain Mutual Ditch was not provided during the <br /> SO-02 process. The engineering evaluation provided on August 14, 2019 does not meet the <br /> DRMS criteria in Rule 6.5 and Section 30 of the Policies of The Mined Land Reclamation <br /> Board(MLRB Policies)for Factors of Safety for Slope Stab ility/Geotechnical Analyses. <br /> Please provide slope stability geotechnical analyses for the four cross-sections shown in <br /> Attachment B meeting the MLRB policy under worst case mine plan conditions by the 60- <br /> day deadline. <br /> a. The Fountain Mutual Ditch slope stability analysis is presented in Appendix A <br /> and Figures 4 and 5 show the requested cross sections based on a recent survey. <br /> B. Please address the following with respect to adjacent roads: <br /> i. The July 26, 2019 Figure 1 cross-section submitted for the Milton E Proby(4.5:1 pit <br /> slope 463'away) engineering assessment is skewed, thereby not showing the steepest <br /> slope(s). The DRMS is also uncertain as to whether the digital elevation model(DEM) <br /> used in Google Earth to generate the profile is current. Please resubmit the profile with <br /> the cross-section perpendicular to the slope and provide some evidence the DEM is <br /> current or use a survey cross-section. Please be aware if any of the slopes are steeper <br /> than 3H.•1 V, the DRAE may require a slope stability geotechnical analyses for this area <br /> meeting the MLRB Policy, Section 30. <br /> a. A recent survey provided in AutoCAD Civil 3D was utilized for the digital <br /> elevation model. Cross section#4 on Figure 3 shows the mining slope of 1.8H:1 V <br /> 990 S. Broadway,Ste.222, Denver,CO 80209 1 303.703.1405 1 www.BrierleyAssociates.com <br />