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' California Department of Transportation July 2, goalpro ect No 400296001 Stockton Maintenance Station, Stockton, California J In well MW-3, Benzene concentration increased from non-detectable levels to 4 9 µ9/1 In well VW-1, concentration of TPH-G increased from 200 µg/1 to 8,300 pg/l Benzene concen- tration increased from 7 4 pg/l to 1,070 pg/l Toluene and ethylbenzene concentrations increased from non-detectable levels to 204 µg11 and 425 µg11, respectively Total xylene concentration in- creased from 5 8 µg11 to 747 pg/1 MTBE concentration increased from non-detectable levels to 83 µg/1 In well VW-2, concentration of TPH-G increased from 130 µg/l to 200 pg/1 Benzene decreased from 807 pg/1 to 4 6 pg/l Toluene decreased from 158 µg/1 to non-detectable levels Ethyl- benzene decreased from 31 pg/l to non-detectable levels Total xylenes decreased from 31 µg/1 to non-detectable levels According to laboratory analytical data for VOCs using EPA method 8260B, 1,2,4- tnmethylbenzene, 1,3,5-trimethylbenzene, and napthalene were detected in samples from on-site • well VW-1 6 RECOMMENDATIONS Based on the results of the First Quarter 2001 groundwater monitoring analytical results, which indicated elevated concentration of TPH-G, TPH-D, and BTEX Ninyo & Moore recommends that quarterly groundwater monitoring continue at the site 7. LIMITATIONS The environmental services described in this report have been conducted in general accordance with current regulatory guidelines and the standard-of-care exercised by environmental consult- ants performing similar work in the project area No other warranty, expressed or implied, is made regarding the professional opinions presented in this report Please note this study did not include an evaluation of geotechnical conditions or potential geologic hazards 0296-01 stocuon draft 1Q0 doc