ARCHIVED REPORTS_XR0002467 - Laserfiche WebLink

Home Browse Search

CLEARWATER ' G R 0 U P I N C • £nw,o—ental Se,v[ccs ' On ber 25 and 26 September 1997 Clearwater supervised the installation of six exploratory soil borings p p (SB-1 through SB-6) to depths between 31 and 36 feet bgs in the vicinity of the former USTs Low to moderate concentrations of gasoline range hydrocarbons were detected in soil samples collected from all soil borings except SB-3 and SB-4 Three of the soil borings were converted to groundwater monitoring ' wells (MW-1, MW-2 and MW-3) Analysis of groundwater samples collected from these wells over four quarters it 1997 and 1998 indicated that dissolved-phase gasoline hydrocarbons have been present in groundwater samples collected from all three wells Hydrocarbon concentrations in MW-2 have only slightly exceeded or have not exceeded method detection limits throughout this period The maximum ' detected concentration of dissolved-phase benzene was 2,200 micrograms per liter (µg/1) in MW-1 on September 29, 1998 2.0 FIELD ACTIVITIES ' 21 Soil Borehole Dnlhng and Soil Sampling On January 11, 1999, Clearwater supervised the installation of three groundwater monitoring wells (MW-4, MW-5, MW-6) by Spectrum Drilling, Inc Using a CME-75 high torque drill rig equipped with 8-mch diameter hollow-stem augers, Spectrum completed three soil borings SB-7, -8, and -9, to 20 feet below ground surface (bgs) All work was conducted in accordance with state and local regulatory guidelines and Clearwater's well drilling and sampling protocols (Appendix A) Prior to ' commencement of work, all on-site personnel attended a health and safety meeting and signed the Field Crew Health and Safety Plan 1 Soil samples were collected from a plastic luted ontmuous core barrel Portiors of each soil sample were retained for classification by a Clearwater visual methods of the iter geologist according to the ' Unified Soil Classification System (ASTM D 2488-93) Sample locations and soil descriptions are shown on the boring logs presented as Appendix B 1 Soil samples were selected for laboratory analysis in collaboration with a representative of San ' Joaquin County EHD Three samples were retained from each boring Samples were collected from the capillary fringe and the most apparently contaminated horizons The soil samples were sealed into collection tubes with Teflon lined plastic end caps Laboratory samples were documented on a chain of ' custody form and placed in a cooler for shipment to Entech Analytical Labs, Inc , a state-certified 1 ' C-178 WELL INsr Ryr 2 May 7, 1999