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United States Postal Service Stockton VST de Maintenance FacRity The preliminary remediation goals (PRGs) presented in Table 2 are risk-based concentrations developed by EPA Region 9; PRGs are for use as screening levels in determining if further evaluation is warranted, in prioritizing areas of concern, in establishing initial cleanup goals, and in estimation of potential health risks. V 4.0 CONCLUSIONS During this investigation, seven exploratory borings were drilled or hand sampled in the area of the four former USTs, diesel fuel dispenser, and associated conveyance piping. In general (the laboratory analytical plan varied depending on the boring location), laboratory analysis of soil samples collected from the exploratory borings �. did not detect TPHg, TPHd, BTEX compounds, fuel oxygenates, TRPH, or VOCs above the laboratory detection limits, with the exception of low levels of TPHd. The TPHd was detected in one of the twelve soil samples analyzed (Boring S-1 at 4 to 41/z feet), at a concentration of 4.8 ppm. Boring S-1 was located within the VMF building adjacent to the waste oil UST remote fill. Metal levels detected are typical of natural occurring background concentrations and do not exceed the residential PRGs. L Higher molecular weight petroleum hydrocarbons, such as diesel fuel, typically exhibit characteristics of lower toxicity and lower mobility in the environment than TPHg, BTEX compounds, or fuel oxygenates. Thus, the residual petroleum hydrocarbons detected do not appear to pose a significant threat to human health or the environment. Since the remote fill location is no longer utilized, we would expect the remaining hydrocarbon levels to degrade naturally over time. Based on these results, the former USTs, diesel fuel dispenser, and associated �. conveyance piping do not appear to have significantly impacted soil quality; no further work appears necessary. +� 4.1 No Further Action Based on the above information and considering the State and Regional Water Lo Quality Control Board guidelines, this site should be considered for no further action status by the San Joaquin County Public Health Services, Environmental Health Division. 5.0 LIMITATIONS This report was prepared for the use of United States Postal Service in evaluating soil quality at the Stockton Vehicle Maintenance Facility at the time of this study. We make no warranty, expressed or implied, except that our services have been performed in accordance with environmental principles generally accepted at this time and location. The chemical and other data presented in this report can change over time and are applicable only to the time this study was performed. We are not responsible for the data presented by others. The accuracy and reliability of geo- or hydrochemical studies are a reflection of the number and type of samples taken and extent of the analyses conducted, and are ` thus inherently limited and dependent upon the resources expended. Chemical analyses were performed for specific parameters during this investigation, as detailed in the scope of services. Please note that additional constituents not analyzed for LOV914EYASSOCIATES Page 4 Environmentat 1 Geotechnical 1 Engineering Services 864-76 V