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17 January 2003 AGE-NC Project 02-0946 Page 2 of 9 The Modesto, Riverbank, Turlock Lake Formations and overlying recent alluvium are the principal sources of domestic ground water in the 13,500-square-mile San Joaquin Valley Ground Water Basin (Basin 5-22). This basin is drained primarily by the San Joaquin River. The nearest surface water feature in the vicinity of the property is the Old River, approximately 2.5 miles west of the property. 2.2. PREVIOUS SITE ASSESSMENT Previous site assessments on the property include: • February 2002 - A geotechnical investigation was conducted at the site by Raney Geotechnical Inc (RGI). During the course of the investigation, soil samples collected from two borings (B4 and B5) were noted as having a "gasoline odor". • May 2002 - Five soil borings (B-1 through B-5) were advanced at the site by Construction Testing & Engineering, Inc. (CTE) to determine the nature and extent of soil possibly impacted by petroleum hydrocarbons. Soil samples collected from three of the five soil borings (B-1, B-2 and B-5) contained concentrations of total petroleum hydrocarbons quantified as gasoline (TPH-g), diesel (TPH-d) and/or motor oil (TPH-mo). The highest detected concentrations were found in soil samples collected from borings B-2 and B-5 at depths of 10 and 15 feet below surface grade (bsg), respectively; however, additional laboratory analysis of the 15-foot sample from boring B-5 did not detect volatile organic compounds(including benzene,toluene,ethylbenzene and total xylenes[BTEX] and methyl tertiary-butyl ether [MTBE]) or polychlorinated biphenyls. • Subsequently, a geophysical (magnetometer) survey of a portion of the site was performed to locate potential anomalies(underground storage tanks [USTs] or other buried structures). • July 2002-Four exploratory trenches(T-1 through T-4)were excavated utilizing a backhoe and three soil probe borings were advanced at the site; the trenches were excavated at locations identified during the magnetic survey as possible USTs or buried structures. Trenches T-1, T-2 and T-4 contained assorted waste material; soil samples from the soil borings did not contain detectible concentrations of petroleum hydrocarbons at the depths sampled. Petroleum hydrocarbons and volatile organic compounds were detected in a grab ground water sample at concentrations of 270 micrograms per liter (µg11) TPH-g, 2.6 µg/l toluene, 2.3 µg/1 ethylbenzene, 27.6 µg/l total xylenes, 3.7 µg11 napthalene, 1.1 µg/l n- propylbenzene, 14µg/l 1,2,4-trimethylbenzene,4.1 µg/l 1,3,54rimethylbenzene and 1.2 pg/l n-butylbenzene; however, the detected concentrations of VOCs do not exceed the state of California Department of Health Services' (DHS) Maximum Contaminant Levels (MCLS) and Action Levels (Als). Analytical results of soil and grab ground water samples are presented in Tables 1 and 2, respectively. Advanced GeoEnvironmenlal.Ine.