SITE INFORMATION AND CORRESPONDENCE

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ChevronTexaco—Vernalis Pump Station,Vernalis,CA. Project No. 06-6102-00-6369-201 June 29,2004 Page 6 of 7 accordance with SJCPHS and SCDER guidelines. Well completion reports will be submitted to the DWR as required. Groundwater samples from the four existing on-site wells,MW-1 through MW-4, and the newly installed wells,MW-5 through MW-9,will be collected and analyzed quarterly for a minimum of four consecutive quarters. Groundwater samples collected will be submitted to Lancaster under chain-of-custody protocol for the following chemical analyses: BTEX by EPA Method 8260B; TPHg by EPA Method 8015 Modified; TPHd by EPA Method 8015 Modified with and without silica-gel cleanup; and PAHs by EPA Method 8270C SIM. To facilitate the use of groundwater samples in a HHSE, SAIC recommends that detection limits for BTEX and PAHs be requested from the laboratory that are lower than the EPA Region IX Preliminary Remediation Goals(PRG). The benzene detection limit for use in a HHSE should be less than the EPA tap water PRG of 0.34µg/L. A detection limit of<0.1 gg/L should be requested for benzene. A detection limit of<1.0 gg/L is adequate for toluene, ethylbenzene, and total xylenes. Groundwater detection limits for all PAH compounds should be requested at<0.01 gg/L except for benzo(a)pyrene and dibenzo(a,h)anthracene,which should be requested at<0.005µg/L to ensure the grab groundwater data is adequate for use in a HHSE. Lower detection limits will be requested once for HHSE purposes during the four monitoring and sampling events scheduled. Groundwater monitoring wells containing SPO or sheen will not be sampled. SAIC will measure and record SPO thickness. This data will be summarized in a table and included in the monitoring and sampling report. SAIC will evaluate any wells observed with SPO and recommend mitigation measures, such as vacuum extraction or the use of an absorbent pad or sock,to evacuate any SPO observed in the wells. Purge water will be drummed and properly disposed of by ChevronTexaco. Groundwater will be collected in general accordance with SAIC field procedures. Task 4.3—Quarterly Monitoring and Sampling Report After receiving the chemical test results, SAIC will prepare a report documenting the sampling procedures and findings. The report will include the following: • A site plan; • Field notes; • Groundwater elevations and flow direction; • A summary of analytical test results; • A tabulation of product thickness and quantity removed, if any; and • Copies of the laboratory certificates of analysis. SAIC will present this report to ChevronTexaco 30 days after receipt of the analytical test results. TASK 5—SUBSURFACE INVESTIGATION REPORT Following receipt of the chemical analytical results, SAIC will evaluate whether soil and groundwater has been delineated on and off the subject site as requested by RWQCB. SAIC will prepare a subsurface investigation report describing all aspects and results of the investigation. The need for additional soil borings or groundwater monitoring wells will be evaluated after collecting data associated with this work plan and routine monitoring.