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' SEC'i19NTHREE <br />field Inuestlgation <br />identify subsurface stratigraphy and to observe features important in evaluation of rock mass <br />properties, such as weathering and fracturing. <br />Drilling observations, and descriptions of the soil and rock encountered during drilling are <br />presented on the borehole logs in Appendix A. <br />3.2.3 Packer Testing Procedures <br />As noted, upon completion of rock coring, packer permeability tests were performed in the <br />bedrock portion of each boring to estimate the in-situ hydraulic conductivity of the bedrock. Test <br />intervals were typically 5 feet to 10 feet long. Five different water pressures were applied for <br />each test at approximately 50%, 75%, 90%, 75%, and 50% of the estimated effective overburden <br />pressure. Table 5.3 provides a summary of the packer permeability test results. Individual test <br />data and results are also presented in Appendix B. <br />3.2.4 Observation Wells <br />Groundwater observation wells, or piezometers, were installed in ten of the twenty-nine borings <br />upon completion of drilling, coring and packer testing. High Plains Drilling, Denver, CO, <br />installed the piezometers under the supervision of URS' field engineer. <br />The total depth of all the piezometers was 10 feet and they corisisted of nine feet of unscreened <br />PVC pipe at the top and one foot of screened (0.01 inches slot size) PVC pipe at the bottom. The <br />2-inch diameter piezometers are shown adjacent to the test boring logs in Appendix A. <br />3.3 TEST PITS <br />A test pit excavation program was conducted to evaluate near surface soil properties, observe the <br />ground water table, and to collect representative soil samples for laboratory testing. A total of six <br />test pits, identified as TP-1 through TP-6, were excavated along the perimeter of the proposed <br />Sharkey's Lake Gravel Pit. The locations of these test pits are shown on Drawing 1. In addition, <br />samples of potential borrow to be used in the backfill mix for the soil-bentonite cutoff wall were <br />collected from a topsoil stockpile southwest of the existing gravel pit processing facility. <br />3.3.1 Excavation Methods <br />The owner, Platte Sand and Gravel, excavated the test pits using a Hitachi 550 trackhoe. The test <br />pits were generally 8 feet to 10 feet long, 5 feet wide, and 6 feet to 10 feet deep. <br />3.3.2 Logging Procedures <br />Concurrent with excavation of the test pits, URS' field engineer prepared field logs for each test <br />pit. Soil samples were visually classified and changes in subsurface stratigraphy were identified. <br />Bulk samples were collected and placed in 5 gallon plastic buckets. Test pit summary logs are <br />provided in Appendix A. <br />I' N*:\PR~OJECCTS~22238240_PLATTE_SAND_GRAVELISUB_OON 2.0 WORD_PROC\PLATTE SANDB GRAVEL GEOTECHNICAL DESIGN REPORT 4.O.DOC\iSNOV-OS\\ 3-Z <br />v~ <br />