COMPLIANCE INFO - Laserfiche WebLink

Home Browse Search

6.0 SUBSURFACE INVESTIGATION 6.1 DRILLING PROCEDURES On May 21, 1997, four 2-inch diameter polyvinyl chloride (PVC) monitoring wells (MW-1 through MW4) were installed near the southwest, southeast, northwest and west site boundaries respectively. The locations were selected in order to determine if the shallow groundwater beneath the property had been impacted by the off-site sources identified in the Site Acquisition Environmental Record Search. The four wells were installed to the depth of 22 feet bgs. Three soil borings were completed at the site on May 22, 1997. Borings SB-1 through SB-3 were drilled at the locations of each proposed site improvement; in the proposed building pad area, the proposed pump island canopy area and the area of the proposed USTs respectively. Borings SB-1 and SB-3 were completed to a depth of approximately 20 feet bgs. Boring SB-2 was completed to a depth of approximately 50 feet bgs in order to evaluate the liquefaction potential of subsurface soils. Monitoring well and boring locations are indicated on Figure 3. The borings were logged and samples were collected by SECOR personnel. The boring logs are presented in Appendix A. P 6.2 SOIL SAMPLING PROCEDURES During auger advancement, soil sampling was performed starting at a depth of approximately two to three feet bgs using an 18-inch long, 2.5-inch inner diameter split spoon sampler lined with three six-inch brass sample tubes. Sampling was performed by driving the sampler into the undisturbed soil beyond the auger cutter head with a 140-pound hammer free-falling from a height of 30 inches until 18 inches of penetration was achieved or until the number of blows required to drive the sampler 6 inches (blow count) exceeded 50. After driving the sampler, the augers were advanced 18 inches and the sampler was extracted. Soil sampling was subsequently completed every 5 feet to the total depth of exploration to develop a description of the subsurface stratigraphy and to obtain characteristic samples for environmental purposes. Upon extracting the sampler, a representative undisturbed soil sample was packaged by placing Teflon sheets over the brass tube and capping the tube with a tight fitting plastic cap. The ends of the tube were then sealed with self-adhering silicon tape, labeled, and placed in an iced cooler JN 40007-088-01 I1ig\nuw\97.06jun\arcotmc.doc 6-1