2016-07-01_REVISION - M1977141 (2)

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1.0 PURPOSE This Summary Report of Engineering Stability Analysis presents the results of the engineering stability analyses performed to assist Aggregate Industries in the final reclamation of the Lyons Quarry in accordance with the original permit and the rules and regulations of the Colorado Mined Land Reclamation Board. The purpose of the engineering stability analysis was to evaluate the geometries, material properties, geomechanical properties, and subsurface conditions associated with the existing highwalls, rock slopes, and fill slopes and to provide recommendations for slope configurations for final reclamation of the site. The details of the engineering stability analysis for the highwall and rock slopes are presented in Attachment A. The details of the engineering stability analysis for the fill slopes are presented in Attachment B. 2.0 PROJECT LOCATION AND DESCRIPTION Lyons Quarry is located southwest of Lyons, Colorado approximately 10 miles north Boulder, Colorado (See Figure 1.1 of Attachment A). The site is just south of Colorado State Highway 7, located in Sections 25 and 26 of Township 3 North, Range 71 West of the 6th Principle Meridian. The quarry is currently inactive and is being evaluated for closure and reclamation. Reclamation would include configuring the highwall and fill slopes to address the potential for instability or other geologic hazards or geological conditions that could potentially impact the site. 3.0 SITE CONDITIONS AND GEOLOGICAL CONSIDERATIONS The Lyons Quarry consists of mined and leveled ground along the north end of the site, adjacent to South St. Vrain Creek, with mined highwalls and overburden waste piles extending less than 1500 feet to the south of the creek (See Figure 1.2 of Attachment A). Mining at the site has ceased except for stockpiling and loading of remaining aggregates. Several one story buildings and processing equipment are present near the entrance of the site. The current use of lands adjacent to the mining activities appears to be range land or Open Space. Bedrock geology at the site consists of a couple hundred feet of sedimentary strata of the Fountain Formation that is intruded by an igneous sill. The igneous sill is 100 to 200 feet thick and is described as dacite in this report. The surficial geology consists of thin deposits of alluvium and colluvium. The structure of the sedimentary strata and intruded dacite sill generally dips 10 to 15 degrees to the east and southeast, but locally the average dip is about 5 degrees almost due south. A fault is mapped at the site 86995/DEN8R017 Page 1 of 5 February 2008 Copyright 2008 Kleinfelder West, Inc.