INSTALL 1997 - Laserfiche WebLink

Home Browse Search

4.0 SUBSURFACE INVESTIGATION 4.1 SOIL BORINGS AND GROUNDWATER MONITORING WELLS Two vertical soil borings (SB-1 and SB-2) were advanced to depths of 51.5 feet bgs onsite on November 21 and December 2, 1996. The purpose of SB-2, that is located near SB-1, was to obtain more reasonable SPT blow counts under the groundwater table for the geotechnical engineering evaluations. The results of the geotechnical evaluations are presented under separate cover. A hydropunch water sample was collected from soil boring SB-1. Three vertical soil borings were drilled to depths of 25 to 27 feet bgs and converted to groundwater monitoring wells j (MW-1, MW-2 and MW-3). The borings and wells were drilled with an 8- to 10-inch hollow- stem auger drill rig. Boring locations are indicated on Figure 3. The borings and wells were logged and samples were collected by SECOR personnel. The boring and well logs are 7 presented in Appendix B. 4.2 SOIL SAMPLING AND PACKAGING Drive samples were obtained from the borings by driving a Standard Penetration Test Split Spoon Sampler (SPT) lined with three 6-inch long brass sampling tubes. The sampler was driven by a 140-pound hammer, free-falling 30 inches. The sampler was advanced 18 inches at each sampling interval or until refusal, and the blow counts required to advance the sampler each 6-inch interval of the 18-inch drive were recorded on the boring logs. Sampler refusal is when the sampler does not advance and appears to bounce when the hammer is lowered. Typically, if a 6-inch interval has more than 50 blows per 6 inches, the hammering is terminated. The blow counts may be correlated to soil consistency and other engineering properties. Relatively undisturbed soil samples were collected at approximately 5-foot depth intervals. Prior to sampling at each interval, the sampler and the brass insert tubes were cleaned in an J Alconox scrub solution, rinsed with tap water, and rinsed a second time in distilled water. J This rigorous cleaning procedure was followed to avoid cross-contamination. Of the three brass sleeves, one brass sleeve from each sample drive was evaluated for the presence of J petroleum hydrocarbons in the field by detectable odors and by using an Hnu PI-101 -+ Photoionization Detector (PID); and one brass sleeve soil sample was then packaged by affixing Teflon sheets on the top and bottom of the sample tube, capping the tube and sealing with Teflon tape. The samples were placed in refrigerated storage and delivered under chain-of-custody to Del Mar Analytical Laboratory in Colton, California for testing. ]N 40007-097-01 4-1