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On D . ecember 19 and 22, 1997, Ramage Environmental collected sod and groundwater-grab samples from eleven locations using a Geoprobe® 5400 Direct-Push Technology (Geoprobe) rig, operated by Fisch Environmental of Valley Springs, California (C-57 License#683865) Field observation and analytical laboratory results indicated that diesel and gasoline hydrocarbons had impacted soil and groundwater beneath the site, the city of Tracy right-of-way (Hamilton Alley) and other private property parcels to the north and east of the site Sod samples collected by the Geoprobe from soil borings located within and in close proximity to the former UST excavation contained the highest concentrations of diesel and gasoline hydrocarbons Petroleum hydrocarbons were detected in soil samples collected at 10 feet bgs at concentrations as high as 1,800 ppm of Total Petroleum Hydrocarbons (TPH)-as-diesel, 400 ppm of TPH-as-gasoline and 5 4 ppm of benzene Methyl tertiary butyl ether (MTBE) was not detected in any of the soil samples analyzed Vertically, the extent of impacted soil was defined to less than 15 feet bgs The most heavily impacted soil was present from lust above the current fgroundwater table at approximately 7 feet bgs to a depth of approximately 12 feet bgs Laterally, impacted soil extended to the north of the site beneath Hamilton Alley and the private property parcels east and north of the site • Groundwater-grab samples collected from all eleven of the sample locations contained detectable concentrations of diesel and gasoline hydrocarbons Petroleum hydrocarbons were detected in close proximity to the former UST excavation at concentrations of 1,300,000 parts per billion (ppb) of TPH-as-diesel, 140,000 ppb of TPH-as-gasoline, 11,000 ppb of benzene and 400 ppb of MTBE Two groundwater-grab samples analyzed by EPA Method 8260 did not contain alcohol- or ether-based oxygenate compounds Some free product was observed during the sod and groundwater sampling in and around the former UST excavation Laterally, impacted groundwater extended to the north and east of the site under Hamilton Alley and private property On October 29, 1998, V&W Drilling, Inc (C-57 License#720904) installed three groundwater monitoring wells (MW-1, MW-2 and MW-3) The locations of the three wells are shown on Figure 2 On November 5, 1998, groundwater samples collected from the newly-installed wells were analyzed for TPH-as-diesel, TPH-as-gasoline, BTEX, MTBE, and four other alcohol-and ether- based oxygenate compounds Only TPH-as-diesel was detected in one of the three wells (MW- 2), at a relatively low concentration of 140 ppb • 4