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BRIERLEY ASSOCIATES Creating Space Underground January 15, 2015 File Number: 514168 -000 Anderson Consulting Engineers 375 East Horsetooth Road, Building 5 Fort Collins, CO 80525 Attention: Brian Smith, PE Senior Project Manager DRMS Title 34 Slope Stability Analyses Rigden Reservoir and Port of Entry Pit Fort Collins, Colorado Mr. Smith, Brierley Associates (Brierley) is pleased to present Anderson Consulting Engineers (Anderson) with the results of a slope stability evaluation of areas in the immediate vicinity of Rigden Reservoir and Port of Entry (POE) pit. Specifically, Brierley evaluated the slope stability of the County Road 40 Right -of -Way and the Interstate 25 Right -of -Way (Figure 1). Our slope stability analyses were performed using: 1) existing information from previous investigations, 2) material strengths based on exploratory borings, laboratory testing, and DRMS typical soil strength parameters, 3) cross - section geometry, observed groundwater and bedrock conditions during construction, and maximum reservoir and pit storage elevations provided by Anderson, and 4) Brierley's understanding of the proposed project. According to section 34- 32.5 -115 of the Colorado Land Reclamation Act for the Extraction of Construction Materials, "The board or office shall not deny a permit except on the following grounds: the mining operation will adversely affect the stability of any significant, valuable, and permanent manmade structures located within two hundred feet of the affected land ". The City of Fort Collins (City) requested slope stability analyses to be conducted for the County Road 40 and Interstate 25 Right -of -Way, both located within two hundred feet of mining related activities. The slope stability analyses will be used to demonstrate that the Rigden Reservoir and POE pit projects will not adversely impact the two structures and to fulfill the City's obligation to the DRMS for the processing of the successor of operator for the mining permits associated with these project sites. Site Description Rigden Reservoir is located approximately %2 -miles northeast of the intersection of Ziegler Road and County Road 40 /Horsetooth Road in Fort Collins, Colorado. Figure 1 shows the project site including the critical cross section locations selected for the two slope stability analyses. The subject project is currently under construction, with the completed goal of creating a water augmentation reservoir located in a previously, partially mined gravel pit. In order to create the desired capacity, excavation of overburden soils and claystone bedrock was necessary. A percentage of excavated claystone was used to create a low- permeability embankment face, 2629 Redwing Road, Ste. 150, Fort Collins, CO 80526 1970.237.4988 1 www.BrierleyAssociates.com