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D E E R E & A U L T 600 South Airport Road, Suite A-205 <br /> Longmont, Colorado 80503 <br /> w 303-651-1468 <br /> schnabel-eng.com I deereault.com <br /> MEMORANDUM <br /> TO: Jeremy Stanton DATE: August 24, 2020 <br /> COMPANY: L.G. Everist, Mountain Division SUBJECT: Response to DRMS Comments on <br /> Cannon Lands Slope Stability <br /> ADDRESS: 7321 E. 88th Ave.,Suite 200, PROJECT L.G. Everist Cannon Lands <br /> Henderson, CO 80640 NAME/NO.: DA201041.00 <br /> FROM: Susan Rainey, P.E., CC: <br /> This memorandum is in response to comments received from the Colorado Division of Reclamation, Mining and <br /> Safety (DRMS)on June 29, 2020 regarding Ragsdale Reservoirs, DRMS File No. M-2020-007, also known as <br /> Cannon Lands. That memo states that for DRMS to accept the Factors of Safety selected by Deere&Ault for <br /> slope stability a site-specific geotechnical investigation of Cannon Lands bedrock was needed. In a phone call on <br /> July 1,2020 with all parties, it was agreed upon to sample the bedrock near borings B-15 and B-18 and test for <br /> strength parameters. The site layout and boring locations are shown on the attached Figure 1A. <br /> Three bedrock samples were collected that were suitable for strength testing. The samples tested were B-15-1 at <br /> a depth of 43.9 feet, B-15-1 at a depth of 50.9 feet and B-18-1 at a depth of 56.8 feet. In boring B-15-1 the upper <br /> sample was collected in a brass sleeve, and the lower sample was collected by coring into the bedrock. Both of <br /> these samples comprised fresh, or un-weathered and theoretically higher strength bedrock. The sample from B- <br /> 18-1 was also collected using a brass sleeve and was taken from the upper weathered or fully softened portion of <br /> the bedrock. <br /> Direct shear tests were performed on each of the samples. The results from the testing are attached and <br /> summarized in the table below. <br /> Bedrock Laboratory Strength Test Results <br /> Test Sample Cohesion Phi' <br /> Hole Depth Unit Type (psf) (degrees) <br /> B-15-1 43.9-44.3 Claystone Sleeve 326 30.3 <br /> B-15-1 50.9-51.5 Claystone Core 769 23.9 <br /> B-18-1 56.8-57.2 Weathered Claystone Sleeve 0 36.0 <br /> Comparing the site-specific strength testing results to the parameters used in the slope stability analyses show <br /> that the laboratory testing values are higher or equal to those used in the analyses. This is shown in the table <br /> below. <br />