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AV Mr. Mark Johnson March 17, 2017 Page 2 From a geotechnical standpoint, the sand and gravel will form the majority of the mine slopes. These soils are generally strong and stable, particularly when dewatered. SITE GROUNDWATER Civil Resources conservatively modeled the groundwater at five feet below the ground surface, based on the geotechnical exploration completed by Drilling Engineers in 2017 and data from Bestway Concrete. STRUCTURES WITH 200 FEET OF DISTURBED AREAS The known, permanent, man-made structures within 200 feet of the proposed mine areas that are not owned by Bestway Concrete &Aggregates are listed below: • WCR 13 I N. County Road 1 (Weld County Public Works)(Larimer County Public Works) • Highway 392 I WCR 68(Weld County Public Works) • Traffic Light(Intersection)(Weld County Public Works) • Overhead Power Line (Western & Eastern Boundary)(PVREA) • Drainage Easements(CDOTIWindsor) • Gas Line(Southern Boundary)(DCP) • Gas Line(Western &Northern Boundary)(XCEL Energy) • Gas Facility(XCEL) • Telephone(West& North)(Century Link) • Pond (West of site)(United Water&Sanitation District) • Cable(West& North)(Comcast Link) • Cable(West& North)(Dark Com) • Water Line (Western &Northern Boundary)(Town of Windsor) STABILITY ANALYSES The stability of the proposed mining limits was evaluated at four sections under anticipated loading conditions around the perimeter of the site and is discussed below The computer program XSTABL was used for the analysis The method for selecting the critical failure surface for each analyzed loading condition is the following. The Modified Bishop's Method of Analysis is used to find the critical failure surface by randomly searching with 12 termination points and 12 initiation points(144 failure circles) with 7 foot line segments over a broad range of the slope surface. This procedure is repeated over different initiation and termination locations until the most critical factor of safety failure surface is identified The range is narrowed and 12 initiation points and 12 termination points (144 failure circles)with 7 foot line segments for the final run of 144 circles to determine the lowest factor of safety. Therefore, prior to submitting the final stability run, at least 288 failure surfaces were analyzed to determine the lowest factor of safety. The four cross-section locations were selected to analyze proposed minimum setbacks for stability of structures using appropriate surcharge loads for the mining limits. The cross sections are modeled with a 1:1 (H.V) highwall. All mining slopes are modeled to be no steeper than 1:1 (H:V). The locations are described below and shown on Figure 1.