WORK PLANS - Laserfiche WebLink

Home Browse Search

Monitoring Well Installation Work Plan DEN'S AUTO REPAIR 308 South El Dorado Street, Stockton, California 1.0. INTRODUCTION At the request of Mr.Den Ueda of Den's Auto Repair,Advanced GeoEnvironmental,Inc(AGE)has prepared this work plan for installation of three ground water monitoring wells in the City of Stockton right of way near 308 South El Dorado Street, Stockton, California (site). The objective of this scope of work is to assess the lateral and vertical extent of petroleum hydrocarbon-impacted soil and ground water to the north and west of the site. The location of the site is illustrated in Figure 1. A plan of the site is illustrated in Figure 2. Background information is summarized in Appendix A. This work plan is prepared in accordance with Central Valley Regional Water Quality Control Board (CVRWQCB)guidelines(AppendixA-Tri-Regional Board StaffRecommendations ForPreliminary Investigations and Evaluation of Underground Tank Sites) for the investigation of underground storage tanks(UST)sites. In addition,this work plan is prepared as directed by San Joaquin County Environmental Health Department(EHD) directive letter, dated 15 April 2010. 2.0. ADJACENT SUBSURFACE INVESTIGATIONS On 08 June 2010, AGE personnel performed a file review at EHD for the property located at 325 South El Dorado Street(Gateway Project). The Gateway Project site is located approximately 100 feet southwest of the former dispenser island location at 308 South El Dorado Street(Den's Auto). In September and October 1999, two 1,000-gallon USTs were removed from the sidewalk of 325 South El Dorado Street. In March 2000, five probe borings (GP 1 through GP5) were advanced in and around the former UST area. Laboratory analysis of soil samples detected total petroleum hydrocarbons as gasoline(TPH-g)at a concentration of 5.9 milligrams per kilogram(mg/kg)in the sample collected from GPI at 26 feet below surface grade (bsg). Ethylbenzene and xylenes were detected in the same sample at concentrations of 0.01 mg/kg and 0.027 mg/kg,respectively; xylene was detected at a concentration of 0.0057 mg/kg in the sample collected from GP 1 at 16 feet bsg. Ground water samples were collected from borings GPI, GP2, GP4, and GP5 at depths of 25 feet, 15 feet, 24 feet, and 17 feet bsg, respectively. TPH-g were detected in the ground water sample collected from GPI at a concentration of 4,800 micrograms per liter (µg/1). Benzene, toluene, ethylbenzene, and xylene (BTEX) were detected in the same samples at concentrations of 7.0 gg/l benzene,4.0 gg/l toluene,23 gg/l ethylbenzene,and 99 gg/l xylene. TPH-g and BTEX compounds were not detected in the ground water samples collected from borings GP2, GP4, and GP5. Condor Earth Technologies,Inc.(Condor)determined the lateral extent of the dissolved plume was defined; however several ground water samples collected may not represent the impacted aquifer, and the vertical extent was not defined. During the installation of soil borings, ground water elevation within the ground water basin was artificially increased by an abundant spring recharge from the El Nino. Advanced GeoEnviron mental,Inc.