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•1L hdo . Do 14 ,93 16 : 54 No .0: 1 P . 03 <br /> IVI t IVI U M H IN U U IVI <br /> CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD • CENTRAL VALLEY REGION <br /> 3443 Routier Road, Suite A Phone: (91t>zss-3000 <br /> Sacramento, CA 95827.1098 CALNET: 8.494-3000 <br /> TO: Wendy L. Cohen FROM: Philip S. 1sorena <br /> Senior Engineer Associate Engineer <br /> DATE: 29 November 1993 SIGNATURE: J✓M 4p �+. <br /> SUBJECT: INTERIM REMEDIAL ACTION PLAN (IRAP) STATUS, STOCKTON <br /> TERMINALS TECHNICAL COMMITTEE (STTC), PORT OF STOCKTON, <br /> SAN JOAQLTL COUNTY <br /> On 24 November 1993, I had a conference call with Messrs. Roy Thtm, STTC Chair, and Steve <br /> Lofholm, Emcon's project manager for the STTC, regarding our 18 November 1993 letter which <br /> transmitted our comments on the IRAP. Our discussion is briefly summarized below. <br /> 1. 1 reiterated that we have previously approved the proposed free product recovery measures <br /> proposed in the IR-AP with the exception of enhanced biodegradation. I also said that the free <br /> product recovery measures should be already implemented and the proposed enhanced <br /> biodegradation .should be implemented as soon as possible. <br /> Messrs. Thun and Lofnolm clarified the salient features of the proposed IRAP measures, <br /> specifically, that air sparging is an important component of the trench and enhanced <br /> biodegradation system and that the system is an interim measure to remediate the most <br /> contaminated areas such as southwest of Time Oil and southlast of ST Services. <br /> 2. I raised my concern regarding the absence of remedial measures to address other areas which <br /> are highly contaminated. One such location is the area southeast of ARCO, specifically at <br /> PS/WC-15. <br /> Messrs. Thun and Lofltolm stated that although the extent of contamination in Zoite A is <br /> almost completely defined, this still does not justify implementing measures such as soil vapor <br /> extraction (SVE) and pump and treat because these remedial methods may not be part of the <br /> final remediation system. They said that due to high ground water in the area, an SVE system <br /> could only work in the summer, at best, making it cost prohibitive, and pump and treat may <br /> be a viable option, but since the hydraulic connection between Zones A, l3, and C is still <br /> being determined and the contamination in Zone A is relatively stable because of the tltitur ng <br /> Out of the sand isopach to the east, installation of a pump and treat at this time is premature. <br /> Phase II work is now being conducted to meet the 4 February 1994 investigation report <br /> submission deadline, and the information obtained from this investigation will be vital to <br /> determining the final remedial measures. They said PS/WC-15 appears to be a good candidate <br /> for a trench system wish enhanced biodegradation and will be considered during evaluation of <br /> this system, <br />