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' Holnam, Inc. 1 ELI Project No. 20945006 Terracon loader and trucked from the site. A haul road is located along the north and east edges of the 1 quarry. SUBSURFACE CONDITIONS 1 Geolocty: The project area is located within the Front Range of the Southern Rocl<y Mountain physiographic providence. The Front Range is a major, upthrust, mountain belt evidenced by large areas of Precambrian (600,000,000 years old or older- igneous and metamorphic rocks. The crystalline Precambrian basemert complex was formed at great depths within the earth's crust and was once covered with thick sedimentary strata. The sediments were uplifted, along with the basement rocks, and folded during the large-scale, crustal movements known a:; the "Great Laramide Orogeny." Since this Late Cretaceous mountain building period 165,000,000 to 100,000,000 years agol, extensive weathering and erosion have removed the majority of the J overlying sedimentary rocks, leaving the present-day topography. The bedrock expos~:d at the site consists of the Pennsylvania Ingleside Formation. This formation is represented in this area by an upper sandstone which is approximately 20 feet thick, an approximate 20-foot thick tense of limestone and a lower sandstone layer. Avery thin soil layer overlies the bedrock in this area. Bedrock Conditions: The bedrock conditions in the quarry consist of an upper red sandstone, which is approximately 20 feet thick, a minable limestone layer and an underlying sandstone layer. The sandstone is blasted to create material varying in size from approximately 3 feet in diameter to fines which are less than the 1/200 sieve. A thin layer of soil overlies the bedrock in undisturbed areas adjacent to the quarry. Laboratory Test Results: Laboratory test results indicate that the excavated bedrock i s nonelastic and exhibits high shear strengths. When compacted to 88 percent of Standard Proc[or Density, the excavated sandstone is relatively pervious have a permeability rate of 65 feet per year. Groundwater Conditions: According to Mr. Paul Thomsen, Holnam's plant engineer, no groundwater was encountered to depths of 50 feet below the surface of the lower sandstone layer in exploration holes drilled by Holnam, Inc. in the quarry. CONCLUSIONS AND RECOMMENDATIONS J Embankment Evaluation: Tests were run on selected bulk samples obtained in this field from existing stockpiles or removed sandstone overburden material. Shear characteristics were J determined from laboratory tests of the overburden sandstone material. Triaxial shear tests 3