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W IN ZLER g KELLY <br /> C Q N S U l T I N G E N G I N E E R S <br /> �r <br /> Ref 03-30OM8030 <br /> January 27, 2004 <br /> Ms. Margaret Lagorio, REHS <br /> F Environmental Health Department <br /> ,,. San Joaquin County—Public Health Services <br /> 304 East Weber Avenue, Third Floor <br /> Stockton, CA 95202-2708 <br /> Re: Workplan for Groundwater Contamination Investigation, California Highway <br /> Patrol Facility,385 West Grant Line Road,Tracy, California, Site Code: 1904 <br /> Dear Ms. Lagorio: <br /> • Winzler&Kelly Consulting Engineers(Winzler&Kelly) has prepared this Workplan for the <br /> installation of one additional deep monitoring well at the above-referenced site in response to an <br /> April 10, 2003 letter(Appendix A), by the Environmental Health Department, San Joaquin <br /> �- County(EHDSJC). The site is located at the intersection of West Grant Line Road and <br /> Buthmann Avenue in Tracy, California(Figure 1). <br /> �- Background <br /> In March 1999, four soil borings were drilled at the site. Groundwater was encountered at 5 to 7 <br /> feet below ground surface(bgs). Soil samples were collected from all four soil borings at depths <br /> 'r of 9.5 to 10 feet bgs and 24.5 to 25 feet bgs. All of the soil samples were analyzed for total <br /> petroleum hydrocarbons as gasoline(TPH-G), and for benzene, toluene, ethyl benzene, and <br /> xylenes (BTEX). The soil samples collected from 24.5 to 25 feet bgs were also analyzed for <br /> methyl tert-butyl ether(MTBE). MTBE was detected in all of the soil samples collected at 24.5 <br /> to 25 feet bgs. MTBE was also detected in groundwater samples collected from the borings by <br /> EPA Method 8260. <br /> In May 18, 2000, one 12,000-gallon gasoline underground storage tank(UST)was removed <br /> from the site. <br /> In June 2000, three monitoring wells (MW-1, MW-2, and MW-3)were installed at the site to <br /> depths of 15 feet bgs. Analytical results indicated MTBE in soil samples collected from <br /> monitoring well borings MW-i and MW-2 at 6 feet bgs. Groundwater sampling of the <br /> monitoring wells detected TPH-G, BTEX, MTBE, and tert-amyl methyl ether(TAME) from <br /> MW-1; benzene,xylenes, and MTBE in MW-2; and MTBE only in MW-3. Subsequent <br /> groundwater sampling in October 2000 of the monitoring wells detected only MTBE in MW-1 <br /> and MW-3. <br /> LW <br /> 495 Tesconi Circle,Santa Rosa,CA 95401-4696 <br /> tel 707.523.1010 fax 707.527.8679 <br /> www.w-and-k.com <br /> LW <br />