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y r t - -- KLEINFELDEH 1 I EXECUTIVE SUMMARY x� I EH3 Construction acting as an agent for Santa Fe Pacific Realty Company, the property f owner, contracted with Kleinfelder. Inc., to further evaluate soil and ground water I conditions at the site where a 2000-gallon fuel storage tank had been removed at 1515 West Weber Avenue in Stockton, California. Petroleum hydrocarbons were detected in cted from the tank excavation by FGL Environmental, soil and ground water samples colle a previous consultant. 1--v r" To further evaluate soil and ground water conditions at the site, Kleinfelder conducted a soil-gas survey; drilled three soil borings and submitted one sample from each boring for chemical analysis:installed,developed,and sampled three monitoring wells; and measured the depth to ground water in the wells to locate the direction of groundwater now. The ` soil-gas survey detected petroleum hydrocarbon constituents in six of 15 samples collected. Petroleum hydrocarbons were not detected in the three soil samples submitted for analysis, with the exception of 5.5 ug/1 toluene in the sample from B-3. Petroleum hydrocarbons -, were not detected in each of the samples collected from the three monitoring wells. However, coliform was detected in the MW-1 sample at 1600 most probable number (MPN)/100 ml -- possibly due to MW-1's proximity to a sewer line. Measured ground water elevations ranged from 83.43 to 85.03 feet, and the ground water gradient and lCleinfeider's direction at the time of the sampling was 1.15 percent to the southwest. e conclusions and recommendations are based on these findings. The results of the soil-gas survey and soil assessment indicate that soil and ground water �.„ adjacent to the excavation are affected by petroleum hydrocarbons. Kleinfelder ' recommends quarterly monitoring of the ground water duality and gradient to assess the t ` effects of seasonal variations and to assess the possibility of contaminants in ground water spreading laterally as well as downgradient due to the low permeability of soil, the shallow ground water gradient, and gradient fluctuations due to tides and/or seasonal changes. Kleinfelder recommends that affected soil and ground water around the excavation be remediated. Soil remediation options that include the treatment of ground water should be considered because of the shallow nature of the ground water. R This executive summary is subject to limitations stated in this report. F15.90.101 1AOL rr copyright i990 Kteinterder, Inc.