ARCHIVED REPORTS_XR0011464 - Laserfiche WebLink

Home Browse Search

2.0 METHODS AND PROCEDURES ' To evaluate the extent of impacted groundwater at the site, monitoring wells MW5 through MW9, MW 11, and MW 12 were installed at the site, and MW 10 was installed off-site to the west. Field activities were performed in general accordance with WHFs Stockton City Taxi ' Cab/Sunland Gasoline 2085 East Fremont Street, Stockton, California Work Plan for the Lateral and Vertical Extent of Soil and Groundwater Contamination- Continued (Revised), dated May 2004. The workplan and addendum were approved by SJCEHD on June 21, 2004. 2.1 Drilling Activities ' From November 10 to November 12, 2004 and November 15 to November 17, 2004, an ATC geologist supervised the installation of MW5, MW6, and MW12 to approximately 90 feet bgs, ' MW7 to approximately 121 feet bgs and MWS through MW 11 to approximately 65 feet bgs. Woodward Drilling, California License C57 710079, installed the wells utilizing a hollow stem auger drill rig. The locations of the monitoring wells are shown on Figure 3. ' Soil samples were collected from the boreholes of MW5, MW6, MW7, MWS, MW9, MW10, MW 11, and MW 12 at five-foot intervals in stainless steel sampling tubes from 5 feet bgs to 70 feet bgs. Sampling was continuous from 70 feet bgs to 90 feet bgs in the borehole of MW6 and from 70 feet bgs. to 92 feet bgs the borehole of MW5. The cored samples and drill cuttings were characterized for soil type, moisture content, and visual evidence of petroleum hydrocarbons. A photo-ionization detector (PID) was used as a field-screening device for the detection of petroleum hydrocarbon vapors in drill cuttings and cored samples. A field geologist logged drill cuttings and soil samples utilizing the Unified Soil Classification System. Descriptions of soil types encountered and sample collection intervals are included on the well logs contained in Appendix A. 2;2 Soil Sample Analyses Selected soil samples were placed in a cooler chilled with ice and delivered under chain-of- custody documentation to State-certified Argon Laboratories Inc. (Environmental Laboratory Accreditation Program Certification No. 2359) in Ceres, California for chemical analyses. Selected soil samples were analyzed by Argon Laboratories for total petroleum hydrocarbons as ' gasoline (TPHg) by EPA Method 8015B; benzene, toluene, ethylbenzene, and xylenes (BTEX) by EPA Method 802113; and methyl tert butyl ether (MTBE), t-butanol (TBA), tertiary amyl methyl ether (TAME), ethyl tertiary butyl ether (ETBE), di-isopropyl ether (DIPE), 1,2- ' dichloroethane (1,2-DCA), and ethyl dibromide (EDB) by EPA Method 926013. 223 Groundwater Monitoring Well Construction The monitoring wells were installed to further assess the lateral and vertical extent of petroleum hydrocarbon impact to the subsurface and to provide measurement points for the determination S:1Enviromenta11283441reportslsum.doc 2 ATC Associates Inc.