ARCHIVED REPORTS_FIELD NOTES AND PERMITS THROUGH 4_4_1997

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• • Levine-Fricke-Recon ENGINEERS,HYDROGEOLOGISTS&APPLIED SGENTISTS property, and two points on the Lincoln Elementary School property. Additional CPT/PIPP step- out locations may be needed depending on the chemical data results from the remaining sampling points. Currently, three additional points have been proposed (15, 16, and 17, as shown on Figure 1) after review of PIPP sample analytical data obtained from initially proposed sampling points, and a fourth contingent point between the Exxon Station and World Savings may also be needed. The general procedure for each of the CPT borings has been to advance the probe down to the top of the A/B aquitard, at a depth of approximately 75 to 80 feet bgs, and to use the CPT logs to identify permeable, saturated intervals within the A-zone aquifer for subsequent PIPP groundwater sampling. Generally, two to four PIPP groundwater samples have been collected from each boring for laboratory analysis for VOCs by EPA Method 8010. The preliminary results from the 10 PIPP locations already sampled are presented in Table 1. Tetrachloroethene (PCE) is the predominant chemical detected in all samples collected. PCE concentrations range from 18 micrograms per liter (µg/1) to 9,100 µg/1, with one detection at a concentration of 25,000 µg/l in a sample collected at depth of 65 bgs from PIPP 100. Lesser concentrations of trichloroethene have also been detected in the majority of PIPP samples. Cis-1,2-dichloroethene has been occasionally detected at comparatively low concentrations. Vinyl chloride has not been detected in any of the PIPP samples. Schedule We are currently analyzing the field and laboratory data generated from this additional field work. Our interpretation of the current data indicates that adequate data now exist, concerning the distribution of transmissive materials within the A zone along the downgradient boundary of LC, to begin scheduling the remaining Phase I IRA field work. Final recommendations for the aquifer testing program will be included as part of an interim data deliverable forthcoming in January 1997. Whether or not the pending CPT/PIPP locations are completed in early January, we are planning to conduct the A-zone aquifer test on January 27 to 31. Groundwater flow modeling based on the aquifer test results will be completed by the end of February. Given the above schedule for tests and modeling, we propose to submit the final Phase I IRA report to the RWQCB on March 28, 1997. The Phase I IRA report will include a summary of the additional subsurface investigation work and will integrate this data into the conceptual model of the proposed IRA for the downgradient edge of LC. The Phase I IRA report will also present a schedule to implement the IRAs and an update regarding the progress of the source investigation work, as you have previously requested. As described in the IRA Work Plan, Phase II IRA work is anticipated to begin while the source investigation work is underway. We will still submit the RWQBSCH.LTR:SRL 3