SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

• MEMORANDUM CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD • CENTRAL VALLEY REGION 3443 Routier Road, Suite A Phone: (916) 255-3000 Sacramento, CA 95827-3098 CALNET: 8-494-3000 TO: Wendy L. Cohen FROM: Philip S. Isorena Senior Engineer Associate Engineer DATE: 29 November 1993 SIGNATURE: SUBJECT: INTERIM REMEDIAL ACTION PLAN (IRAP) STATUS, STOCKTON TEPAIINALS TECHNICAL COMMITTEE (STTC), PORT OF STOCKTON, SAN JOAQUIN COUNTY On 24 November 1993, I had a conference call with Messrs. Roy Thun, STTC Chair, and Steve Lofholm, Emcon's project manager for the STTC, regarding our 18 November 1993 letter which transmitted our comments on the IRAP. Our discussion is briefly summarized below. 1. I reiterated that we have previously approved the proposed free product recovery measures proposed in the IRAP with the exception of enhanced biodegradation. I also said that the free product recovery measures should be already implemented and the proposed enhanced biodegradation should be implemented as soon as possible. Messrs. Thum and Lofholm clarified the salient features of the proposed IRAP measures, specifically, that air sparging is an important component of the trench and enhanced biodegradation system and that the system is an interim measure to remediate the most contaminated areas such as southwest of Time Oil and southeast of ST Services. 2. I raised my concern regarding the absence of remedial measures to address other areas which are highly contaminated. One such location is the area southeast of ARCO, specifically at PS/WC-15. Messrs. Thun and Lofholm stated that although the extent of contamination in Zone A is almost completely defined, this still does not justify implementing measures such as soil vapor extraction (SVE) and pump and treat because these remedial methods may not be part of the final remediation system. They said that due to high ground water in the area, an SVE system could only work in the summer, at best, making it cost prohibitive, and pump and treat may be a viable option, but since the hydraulic connection between Zones A, B, and C is still being determined and the contamination in Zone A is relatively stable because of the thinning out of the sand isopach to the east, installation of a pump and treat at this time is premature. Phase II work is now being conducted to meet the 4 February 1994 investigation report submission deadline, and the information obtained from this investigation will be vital to determining the final remedial measures. They said PS/WC-15 appears to be a good candidate for a trench system with enhanced biodegradation and will be considered during evaluation of this system.