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, r. < <07 July 2003 AGE-NC Project No 95-0142 r � Page 6 of 7 ' to 3X1.0-7 cm/sec, and average porosity of 43% (Appendix C) ' Based upon analytical results of soil samples collected during the investigation of the former - UST area,it appears that hydrocarbon impacted soil extends approximately 30 feet north and ' 10 feet south of the former TK1-90 UST excavation with a width of approximately 30 feet The impacted soil appears to be distributed throughout the entire vadose zone However, the greatest concentrations of hydrocarbons are present within the smear zone at depths rbetween 35 and 45 feet bsg • The majority of the unsaturated, hydrocarbon-impacted soil resides below former UST ' TK1-90, to a depth of 30 feet below surface grade (bsg) Saturated hydrocarbon-impacted soil extends to a depth of 80 feet bsg, however, below 40 feet bsg, hydrocarbon concentrations generally decrease with depth The mass of hydrocarbons in the unsaturated ' soil is greater than the saturated soil, as shown in Figures 5 and 6 (mass calculation in Appendix D) ' A release of petroleum hydrocarbons, BTEX and MTBE occurred from the former UST TK1-90 Once released to the subsurface, the contaminants migrated to a vertical depth of approximately 60 feet bsg (ASB6) creating a smear zone, at which point the contaminants �. dissolved and migrating,east to MW-4 High concentrations of BTEX compounds were detected in three water monitoring points, VW-1, EW-1 and VW-3 Lower concentrations of BTEX and MTBE compounds were detected in water monitoring points west and ' northeast of the UST release at well VW-4 and VW-2 • Analytical results of ground water sample collected within June 2003, from wells MW-1 to ' T MW-3 and EW-1, EW-2 and VW-1 for chemical analysis, including metals, are included in Appendix E • The dissolved MTBE has migrated southeast from the release site as former UST TKl-90, ' east in the depths above 70 feet to well MW-5, and vertically to well MW-7 at 70 feet bsg Trends of dissolved concentrations of chemicals in well verses date of sampling are included S in Appendix,F • Drinking water around and at the site is currently supplied by the wells maintained by California Water Service Company (Cal-Water) Representatives of AGE performed a ' reconnaissance of visually,observable potential receptors within a 2,000-foot radius of the above referenced site Based on a map entitled Water System of Stockton, published by Cal- Water in' 1996, municipal water well Station No 30 was located approximately 1,000 feet ' east of the site, at Scotts Avenue and American Street (on Mormon Slough) According to Cal Water personnel,this well was permanently abandoned A second Cal-Water municipal water well'Station 37-was located approximately 2,000 feet southeast of the site, at the ' intersection of Anderson Street and Center Street This well was also permanently off-line . The map did not indicate any other municipal wells maintained by the City of Stockton or ' Cal Water located within 2,000 feet of the site Advanced GeoEnvi ran mental,Inc k 1� A