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PHASE H SOIL INVESTIGATION 23390 FLOOD ROAD LINDEN, CALIFORNIA L 1.0 INTRODUCTION This report presents a summary of field methods and results from a soil investigation performed by Roy F. Weston, Inc. (WESTON) on behalf of Hyponex Corporation at their facility located at 23390 Flood Road near Linden, California (Figure 1). The purpose of this investigation was to evaluate the potential presence and extent of petroleum-impacted soil in the vicinity of a former underground storage tank(UST)excavation. All work was performed in accordance with the WESTON Site Contamination Workplan (SCW) dated March 30, 1994, which had been approved by the San Joaquin County Environmental Health Division (EHD). 2.0 SITE BACKGROUND The Hyponex Corporation currently operates an organic blending and bagging facility on the subject property which consists of approximately 26 acres. A site map showing the approximate locations of pertinent features including the vehicle maintenance shop, leach field, and improvements is included as Figure 2. The property is located in a relatively hilly, rural part of San Joaquin County, 13 miles east of Stockton and is surrounded by agricultural and undeveloped land on all sides. According to the San Joaquin County Flood Control District map L entitled "Line of Equal Depth to Water in Wells, Spring 1993" depth to water in the vicinity of the site is greater than 170 feet. In August 1990, two 10,000 gallon diesel tanks and one 1,000 gallon gasoline tank (and all associated piping) were removed from the north portion of the subject property near the shop and appropriately disposed of. Approximately 37 cubic yards of soil was excavated in conjunction with removal of the three USTs. During removal the EHD representative onsite noted that all three steel tanks were in poor condition. Analytical results from a soil sample(#4) collected from beneath the southeast portion of one of the diesel tanks at 15 feet below ground surface (bgs) indicated a total petroleum hydrocarbon as diesel (TPH-D) concentration of 2,100 mg/Kg. The previous sampling locations are shown relative to the former tank excavation and the soil borings installed during the current investigation on Figure 3. The following work was performed to evaluate the full extent of impacted soil surrounding sample location #4, if any. L 3.0 INVESTIGATION SUMMARY The site investigation consisted of collecting multiple soil samples from the subject property for Lanalyses of various organic compounds. A detailed description of field sampling procedures is included as Appendix A. All work was performed under the direction of a California Registered Geologist and all analyses were conducted by a laboratory certified by the State of California to perform the required analyses. A permit for the construction of the soil borings was obtained from EHD prior to installing soil borings. RX%RrrSUfMNEX.wr 1 nsm,%