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; 1 ' 29 March 2004 AGE-NC Project No. 97-0327 ' Page 8 of 12 ' Since May 2000, TPH-g has been detected only in well MW-2 at concentrations as high 490 micrograms per liter(µg11), in August 2000. TPH-d has been detected in wells MW-1 through MW-4 at concentrations as high as 430(µg/1);however,the highest on site concentration ofTPH-d ' (1,900 µg11)was detected in a P-8 grab ground water sample collected from 51 to 55 feet bsg in Tune 1999. Since May 2000,various BTEX compounds have been detected only in well MW-2 at W.erglvery low concentrations. With the exception of benzene, the concentrations of BTEX compounds in on-site ground water monitoring wells MW-1 through MW-4 were detected below the California ' Department of Health Service's(DHS) Maximum Contaminant Levels (MCL) for drinking water; benzene has been detected on five separate occasions(Table 2),but exceeded the MCL only twice, at concentrations of 6.2 µg/1 (August 2000),and 1.5 µg/l (July 2002). ' Low concentrations of MTBE have been detected from wells MW-1 and MW-2. MTBE concentrations in well MW-1 have not exceeded primary and secondary MCLs, and MTBE has not ' been detected in well MW-1 during the last three monitoring events.MTBE concentrations in well MW-2 generally have fluctuate around the primary MCL value of 13 µg11 (Table 2); the maximum MTBE concentration detected utilizing EPA Method 8260 was 16 µg/1. Consistentlylow occurrences of 1,2-DCA have been detected from wells MW-1 MW-2 and M -4 W at concentrations as high as 6.8 µg11 (Table 2); the 1,2-DCA concentrations detected in water samples at the site were above the MCL of 0.5 µg11. ' Since September 2001, consistently low occurrences of TBA have been detected only from well MW-2 at concentrations as high as 48 µg/l, which is slightly above the DHS Action Level (AL) of 12 µg11; action levels are health-based advisory levels and not enforceable standards. TBA has not ' been detected in well MW-2 during the last two monitoring events. Laboratory analysis of water samples from domestic water wells located at 451 and 452 North Lillian ' Avenue did not detect any constituents of concern. ' 6.0. SENSITIVE RECEPTOR SURVEY Drinking water near the site is currently supplied by the City of Stockton municipal well system.The _municipal wells in the site area are maintained by California Water Service Company(Cal-Water). Based on'a map titled Water System of Stockton, published in 1996 by Cal-Water, no municipal - water wells are located within a 2,500 foot radius of the site. On 26 December 2000,AGE contacted the office of Cal-Water, and confirmed that there were no municipal water wells within a 2,500 radius of the site.•