2012-09-06_REVISION - M2008070 (25)

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Design and Operations Plan October 24, 2011 Western Gravel E & P Waste Disposal Facility Page 15 of 51 5 to 10 trucks per day and a peak traffic flow of approximately 50 to 80 trucks per day for 10 day to two week periods that occur approximately two times per year. Since RBCL is the closest landfill facility to WG, WGDF may anticipate similar traffic levels. WG gravel operations employees are expected to operate the proposed landfill. Employment of additional employees for landfill operations is anticipated to be minimal. The March 2009 environmental analysis and subsequent associated SUP approval conditions are deemed appropriate and applicable to the proposed reclamation landfill. The existing Rio Blanco County Road and Bridge Department Right -of -Way Access Permit is included in Appendix A and environmental assessment report is included in Appendix D. 2.4 ENGINEERING DATA A preliminary assessment was conducted during summer and fall 2010 in order to evaluate the feasibility of locating a landfill on the Phase 1 mining area at WG. Field reconnaissance activities included observations of topography, drainages, surface water, surface soils, bedrock outcrops, and surrounding vicinity. Test pits were excavated and boreholes advanced in order to evaluate subsurface conditions (e.g. soils, bedrock, groundwater). WG excavated test pits and Precision Sampling of Colorado Springs, Colorado provided borehole drilling services. Field assessment activities are discussed below. 2.4.1 Test Pits Two test pits (TP -1 and TP -2) were excavated within Phase 1 of the gravel mine The Phase 1 footprint is configured into two legs. The first leg (Leg 1) trends west to east with a second leg located to the east. The second leg (Leg 2) trends from north to south. TP -1 was located at the north end and west side of Leg 2 and TP -2 at the approximate mid -point of Leg 1. The purpose of excavating test pits was to characterize near surface soil and bedrock materials and to collect soil samples for geotechnical laboratory testing. TP -1 and TP -2 locations are shown on Figure 3. TP -1 was excavated at approximately 5,828 feet msl in order to evaluate overburden materia is in an unmined area that had been stripped of topsoil and TP -2 was excavated at the base of the mining area at approximately 5,810 feet msl to evaluate underlying bedrock materials. Subsurface conditions encountered in TP -1 appeared relatively uniform and soils consisted of natural clays from ground surface to the excavation base at approximately 5 feet below ground surface (bgs). The clays encountered in the test pit were slightly sandy to sandy, low to moderately plastic, stiff, dry to slightly moist, and light brown to brown in color. Based upon laboratory test results, the collected soil sample classified as a CL soil in accordance with the Unified Soil Classification System (USCS). TP -2 was excavated approximately 5 feet into the mined pit base following gravel removal. The pit base was approximately 10 to 15 feet below original ground surface. Encountered bedrock consist ed of a layer of claystone overlying sandstone of the Wasatch Formation. Claystone extended from the bedrock surface to approximately 2 feet bgs and is underlain by sandstone that extended to the test pit bottom. The claystone was slightly sandy to sandy, low to moderately plastic, weathered to hard, slightly moist to moist, and brown to reddish brown in color. Based upon laboratory test results, the collected claystone samples classified as CL soils in accordance with the USCS. The underlying sandstone was silty, non - plastic, hard, dry to slightly moist, and light brown to gray in color. Based upon laboratory test results, the collected sandstone samples classified as SM soils in accordance with the USCS. NWCC, Inc.