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. v rE�ri�t+�ErrEr Mr. Charles Leubner 6 February 1998 Page 4 equilibrate at least 48 hours, the monitoring well will be sampled. Immediately prior to sampling, at least three well volumes of water will be purged from the well. All development and purge water will be containerized in 55-gallon drums,labeled and stored on site for subsequent disposal. During purging of the wells, field parameters (pH, electrical conductivity and temperature) will be monitored. Purging will continue until field parameters have stabilized or a minimum of three well volumes are removed. Samples will be collected in containers obtained from and prepared by the analytical laboratory according to the requirements for the specific analysis. After the samples are collected, the bottles will be immediately sealed and labeled. The samples from each well will be identified with a unique sample number, the project number, date and time collected, sample location and sampler's name. After labeling, each sample bottle will be placed in a chilled ice chest delivered under chain-of-custody protocol to a State-certified laboratory. Task 2 -Laboratory Analyses Three soil and one groundwater sample will be analyzed for total petroleum hydrocarbons as gasoline(TPH-G)by EPA Method 8015 and benzene,toluene,xylenes and ethylbenzene by EPA Method 8020. The groundwater sample will also be analyzed for the presence of fuel oxygenates by EPA Method 8260. Task 3—Submit Groundwater Investigation Report Following receipt of laboratory results for soil and groundwater samples, a report will be prepared presenting the results and conclusions of the investigation. If hydrocarbons are not detected in groundwater, the US EPA Vleach Model will be used to evaluate the potential impacts on groundwater of hydrocarbons remaining in the soil. If hydrocarbons are detected in groundwater, the ASTM RBCA Model will be used to evaluate risk associated to humans from inhalation exposures to the hydrocarbons present in groundwater. The report will include a site map showing the location of monitoring well MW-1, a description of sampling protocol, and tabulated results from the soil and groundwater analyses. It will also include the results of the groundwater impact analysis and a recommendation of future action. SCHEDULE Because the Stockton Unified School District intends to solicit bids for conducting the site investigation, a schedule for completing the work cannot be provided at this time. However, once a consultant has been selected, the District will request that the field investigation be