Appendix A - Geotech - Part 1.pdf

This is a Geotechnical Report detailing subsurface exploration and recommendations for a building addition and pavement construction at Hefner VA Medical Center in Salisbury, North Carolina. Geoscience Group, Inc. completed the investigation on behalf of RPA Design, P.C. under Project No. CH09.0088.GE, with the report dated November 24, 2009.

The exploration included eight soil test borings (B-1 through B-8) advanced to depths of 10-35 feet, two asphalt cores (AC-1 and AC-2) measuring existing pavement thickness, and three soft digs (SD-1 through SD-3) to locate underground utilities. Standard Penetration Tests were performed at designated intervals, and split-barrel soil samples were recovered for classification and laboratory testing. Laboratory analysis included natural moisture content determination, Atterberg Limits testing, Standard Proctor compaction testing, and California Bearing Ratio (CBR) tests on bulk samples from boring B-2. The subsurface profile revealed an upper topsoil and roots layer, existing fill materials (silty clay, clayey silt, silty sand) from approximately 2½ to 8 feet depth, residual soils (silty clay, sandy silt, silty sand) extending to 10-27 feet depth, partially weathered rock at 17-27 feet depth, and groundwater encountered at approximately 28 feet in boring B-5. Key recommendations include a shallow foundation system with spread footings bearing on suitable residual soils at net allowable bearing pressure of 3,000 PSF; a slab-on-grade floor system with modulus of subgrade reaction of 120 PCI; a flexible asphalt pavement system consisting of 1-inch Type S surface course, 1½-inch Type I intermediate course, and 8-inch aggregate base course; proper site preparation with removal of unsuitable materials; compaction of fill to at least 95-98 percent Standard Proctor maximum dry density; and observation programs during construction including footing excavation verification, proofrolling, and field density testing.