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iSite Background Information SHOCKEY AND SONS TRUCKING ' 850 Milgeo Avenue,Ripon, California. ' The site is located on the west side of Milgeo Avenue at the intersection with Wilma Road, adjacent to Highway 99. The property is zoned as industrial and is presently utilized as a distribution warehouse. Local land use in the immediate vicinity of the site is agricultural and industrial; tresidential areas are located south of the site. The site is further described as being located in the southeast quarter of Section 19,Township 2 South,Range 8 East,Mount Diablo Base and Meridian (Manteca Quadrangle, 7.5-Minute USGS Topographic Series, 1968, photo revised 1987). SITE DESCRIPTION A former truck fueling system operated on the site for approximately 30 years. Currently a pool construction company operates a materials staging warehouse on the site. The site consists of two ' wood-frame warehouse building structures and an asphalt paved and rock covered vehicle storage area. Local land use in the immediate vicinity of the site is agricultural and industrial; residential areas are located south of the site. . UNDERGROUND STORAGE TANK REMOVAL 1 It is our understanding that six USTs were removed from three separate excavations on the property ' in April 1994: one waste oil UST, one diesel UST and four unleaded gasoline USTs. Petroleum hydrocarbons were detected in soil samples collected from beneath the USTs at the time of removal. Soil excavated during the UST removal was used to backfill each excavation. Clean soil was ' imported to "cap" each excavation. ' PREVIOUS SUBSURFACE INVESTIGATION The following is a brief summary of site assessment activities: • In December 1995, AGE advanced five soil probe borings at the site. Free hydrocarbon ' product was encountered in ground water samples collected from the site; however, soil samples indicated that hydrocarbon-impacted soil was limited to the capillary fringe or lower vadose zone. Locations of the probe borings are illustrated on Figure 2. ' In June 1996, AGE installed four ground water monitoring wells. • On 29 July 1999,a total of six soil probe borings(P6 through P 11)were advanced at the site tand off-site to the north,east and northwest of the former UST location.TPH-d was detected • in all five of the grab ground water samples analyzed, at concentrations from 430 µg/l to 1,100 pg/l. TPH-g was detected in three soil samples analyzed at concentrations as great as ! Advanced GeoEnvironmental,Inc.