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o <br /> CONSULTANTS I NC \ <br /> G E O T E C H N I C AL ❑ ENVIRONMENTAL ❑ MATERIALS ®� <br /> i <br /> Project No S8475-06-24J lJ llE C F'f <br /> �April 22, 2004 �1J <br /> ' <br /> Mr Saiyed S Ali JUL Z 5 2004 <br /> California Department of Transportation ENVIR(AMENT hEALTH <br /> Central Sierra Environmental Services Branch PERMIT/SERVICES <br /> Post Office Box 2048 <br /> Stockton, California 95201 <br /> Subject STOCKTON MAINTENANCE STATION <br /> SAN JOAQUIN COUNTY, CALIFORNIA <br />' CONTRACT NO 43AO078 <br /> TASK ORDER NO 10-987901-MU <br /> GROUNDWATER MONITORING REPORT -FIRST QUARTER 2004 <br />' Dear Mr All <br /> In accordance with Caltrans Task Order No 10-987901-MU, dated February 22, 2002, Geocon <br /> Consultants, Inc has provided groundwater monitoring services at the Stockton Maintenance Station <br /> located at 1604 South B Street in San Joaquin County, California (the Site) The Site consists of a <br /> Caltrans maintenance facility utilized for the storage of vehicles and equipment used for the <br /> maintenance of California highways The scope of services provided by Geocon included depth to <br /> groundwater measurements, the sampling of fourteen monitoring wells, and the submittal of the water <br /> samples to a California-certified laboratory for analytical testing The site location is depicted on the <br /> Vicinity Map, Figure 1 <br /> BACKGROUND <br /> In December 1989, one 5,000-gallon diesel underground storage tank (UST) and one 10,000-gallon <br /> gasoline UST, two pump islands and associated product piping were removed from the Site Analytical <br /> results of soil samples collected from the UST excavation indicated total petroleum hydrocarbons as <br /> gasoline and diesel (TPHg and TPHd) concentrations up to 2,000 and 58 milligrams per kilogram <br /> (mg/kg), respectively In September 1993, one 115-gallon backup diesel generator UST was removed <br />' from the Site Soil discoloration and odors were not noted during the 1993 UST removal activities <br /> TPHd and benzene, toluene, ethylbenzene and total xylenes (BTEX) were not detected in the soil <br /> samples collected from the UST excavation and stockpile Permits and/or closure documentation for <br />' the 1993 UST removal were not made available by Caltrans or the San Joaquin County Environmental <br /> Health Department (SJCEHD) The former UST locations are presented on Figure 2 <br />' Twelve groundwater monitoring wells (MW-1 through MW-12) and two vapor extraction wells (VW- <br /> 1 and VW-2) were installed at the Site between 1992 and 1996 Quarterly groundwater monitoring has <br /> been conducted at the Site since April 1992 for wells MW-1, MW-2 and MW-3, since May 1995 for <br /> wells MW-4 through MW-8 and VW-1, and since February 1996 for wells MW-9 through MW-12 and <br /> VW-2 Maximum TPHg, TPHd and benzene concentrations of 54,000, 11,000 and 13,700 micrograms <br /> per liter (pg/1), respectively, have been reported for the groundwater samples <br /> i <br />' 3160 Gold Valley Drive, Suite 800 ❑ Rancho Cordova California 95742 13 Telephone (916) 852 9118 0 Fax (9161 852 9132 <br />