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APPENDIX A <br /> HISTORICAL BACKGROUND <br /> SHOCKEY AND SONS TRUCKING <br /> 850 Milgeo Avenue, Ripon, California <br />' The site is located on west side of Milgeo Avenue at the intersection Wilma Road, adjacent to <br /> Highway 99 The property is zoned industrial and is presently utilized as a distribution warehouse <br /> Local land use in the immediate vicinity of the site is agricultural and industrial, residential areas are <br />' located south of the site The site is further described as being located in the southeast quarter of <br /> Section 19, Township 2 South , Range 8 East, Mount Diablo Base and Meridian (Manteca <br /> Quadrangle, 7 5-Minute USGS Topographic Series, 1968, photo revised 1987) <br />' SITE DESCRIPTION <br /> A former truck fueling system operated on the site for approximately 30 years Currently a pool <br />' construction company operates a materials staging warehouse on the site The site consists of two <br /> wood-frame warehouse building structure and an asphalt-paved and rock covered vehicle storage <br /> area Local land use in the immediate vicinity of the site is agricultural and industrial,residential areas <br />' are located south of the site <br />' UNDERGROUND STORAGE TANK REMOVAL <br /> It is our understanding that six USTs were removed from three separated excavations on the property <br />' in April 1994 one waste oil UST, one diesel UST and four unleaded gasoline USTs Petroleum <br /> hydrocarbons were detected in soil samples collected from beneath the USTs at the time of removal <br /> Soil excavated during the UST removal was used to backfill each excavation Clean soil was imported <br />' to "cap" each excavation <br /> PREVIOUS SUBSURFACE INVESTIGATION <br />' The following is a brief summary of site assessment activities <br /> • Irl December 1995, AGE advanced five soil probe borings at the site Free hydrocarbon <br /> product was encountered in ground water samples collected from the site However, soil <br /> samples indicated that hydrocarbon-uxipacted soil was limited to the capillary fringe or lower <br /> vadose zone (Tables 1 and 2) Locations of the probe borings are illustrated on Figure 2 <br />' • In June 1996, AGE installed four ground water monitoring wells <br /> • On 29 July 1999, a total of six soil probe borings (P6 through P11) were advanced at the site <br /> and off the site north, east and northwest of the former UST location TPH-d was detected <br /> in all five of the grab groundwater samples analyzed at concentrations from430 Rg/l to 1,100 <br /> Rg/1 TPH-g was detected in three soil samples analyzed at concentrations as great as 350 <br /> milligram per kilogram(mg/kg) in soil sample P 10-20' TPH-g was detected in soil from 15 <br /> feet and 25 feet bsg at concentrations of 160 mg/kg and 14 mg/kg, respectively TPH-g was <br />