ARCHIVED REPORTS_XR0012724 - Laserfiche WebLink

Home Browse Search

121 f :..., -' M"3rrmm s � s .J° ' Ate. 1=b i 2.4 FIELD INVESTIGATION ?,.1 I)RIFI,ING Ri�FD SOTTO SAMPT�It7G �'i on March 28, 1991, two borings (B-5 and B-b) were driiled and sampled at tho Site (Figure 2) . Boring B-5 was terminated at a depth of about 31.5 feet below ground surface (bgs) . The planned termination depth of boring B-b was also approximately 30 f4-et bgs. flowever, based on elevated concentrations of hydrocarbon vapor encountered during drilling, boring B-G was advanced to a depth of 51.5 feet bgs. The borings were drilled by West Hazmat Drilling Corp. of Rancho Cordova, California (Licence No. 554979; C-57 Water Well Drilling) , under the supervision of an EAI engineer and geologist. The borings were drilled using S-inch diamet. r continuous flight h.ollow stem augers. The borings were logged in accordance with the Unified Soil Classification System (see Appendix A) . Soil samples were obtained from each boring beginning at approximately five feet bgs, and at approximately 5-foot intervals thereafter, until termination. The samples were collected using six 2.5-inch diameter 3-inch long brass tubes mounted within a split-spoon drive sampler employed in advance of the augers. After sample recovery, the ends of the lowermost tube were covered with aluminum foil and plastic caps taped over the ends. Prior to use, all tubes were washed in a solution of Alconox detergent and tap water, double rinsed with tap water, - and then with distilled water. The samples were labeled with the sample point identification, date, time and depth interval, individually sealed in "Ziploc" plastic bags, and immediately placed into an ice chest chilled with crushed ice as well as i frozen blue ice. The samples were kept chilled until delivered to the laboratory for analytical testing. All samples delivered to the laboratory were logged on chain of custody record forms (see Appendix B) . 3 After sample recovery, a Bacharach TLV sniffer calibrated against a hexane standard was used on soil contained in the second tube from the bottom of the shoe, at each sampling interval within the borings, to determine if volatile hydrocarbon vapors were emanating directly from the soil. Each sample was placed in an airtight "Ziploc" plastic bag. The ' samples were allowed to sit in the sun, and then the head space in the bags was analyzed using the TLV sniffer. The results of this testing were recorded on the boring logs (see Appendix B) . The borings were backfilled from termination depth to grade using a 10:1 ratio of cement to water with 3-5 percent bentonite added. Project No. 1232 -2- FiVV1ROA' EiVT.11,,1UDIT,INC.