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Geotechnical Engineering Report Terracon Rollin Consulting Terracon Project No. 21025057 Selected bedrock samples were tested for the following engineering properties: • Grain size Maximum dry density -optimum • Plasticity Index moisture content relationship • Remolded flexible wall permeability SITE CONDITIONS Several existing buildings, oil tanks, and access roads occupy portions of the site. The site was bounded on the north and west by irrigation ditches, on the east by Weld County Road 25, and on the south by Weld County Road 18. SUBSURFACE CONDITIONS Soil and Bedrock Conditions: As presented on the Logs of Borings, surface soils to depths of about 28 to 42 feet consisted of native soils comprised of sands with varying amounts of silt, gravel and cobbles, and clays with varying amounts of sand, gravel and cobbles. claystone and/or sandy siltstone bedrock was encountered beneath the native soils and extended to the full depth of exploration. Field and Laboratory Test Results: Field test results indicate that the claystone bedrock is medium hard to very hard in hardness. Upon review of the physical properties of the subsurface claystone and sandy siltstone materials, clay and silt fines ranged from about 61 to 98 percent, liquid limits (LL) ranged from no value to 52, and plasticity indices (PI's) ranged from non-plastic to 29. The no value liquid limit and non-plastic value is associated with the claystone/sandy siltstone sample from Boring No. 5. The claystone materials classified as fat clay (CH), lean clay (CL), and sandy silt (ML) according to the Unified Soils Classification System, and A-4, A-6, and A-7-6 according to the American Association of State Highway and Transportation Officials (AASHTO) classification system with group indices ranging from 0 to 32. The claystone bulk samples from the borings were combined and submitted for additional laboratory testing. A maximum dry density of 107.5 pound per cubic feet (pcf) and an optimum moisture content of 18.0 percent was determined for the combined claystone sample according to ASTM D698/ AASHTO T-99. The graphical results are included in Appendix B. A remolded flexible wall permeability test was performed on the combined claystone materials. The claystone sample was remolded to approximately 95 percent of the maximum dry density as determined by ASTM D698/ AASHTO T-99 and conditioned near 3