SITE INFORMATION AND CORRESPONDENCE_FILE 2

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Page 1 of 3 Lori Duncan [EH] From: Murphy, Mike [mmurphy@cambria-env.com] Sent: Wednesday, September 27, 2006 12:03 PM To: Lori Duncan [EH] Subject: RE: 6131 Pacific Ave., Stockton Lori-I forwarded your questions regarding extraction well selection to our engineering department for their input. Here is the response: "At the time we setup temp system, depth to water was at 35 feet below grade. VEW-2 data is five years older than VEW-7 data. VEW-7 vadose zone detection is -5 shallower(19 feet below grade)than VEW-2. Temp systems are difficult to operate continuously if they are pulling in groundwater. We opted for VEW-7 so as to get rhe best chance at good run-time and mass removal. Initial vapor concentration from VEW-7 was 23,980 ppmv (PID). We've removed 478 pounds of TPHg so far. The final vapor concentration from VEW-2 at the end of testing in 2004 was 3,800 ppmv." It seems that based on available data and other factors, the best use of the temp system is to extract from VEW- 7. Once we get the DPE system installed, we will be extracting from additional areas which should address your concerns. Sounds like we are pulling from what is the highest yielding well that still allows for efficient operation of the temp system. We are sampling once per month with two samples collected during August. Influent concentrations ranged from 5,800 ppmv to 11,000 ppmv(laboratory results)during this period. Thanks, Mike Mike Murphy Senior Project Scientist Cambria Environmental Technology, Inc. 270 Perkins Street, Sonoma, CA 95476 Phone: 707.933.2367 FAX: 707.935.6649 Cell: 510.385.3116 A Woman-Owned Business This a-malt may contain confidentiatandprivi/eged material for the sole use of the intended recipient.Any review or distribution by others is s&ictty prohibited.If you are not the intended rectpientplease contact the sender and delete all copies. From: Lori Duncan [EH] [mailto:lduncan@sjcehd.com] Sent: Tuesday, September 26, 2006 9:01 AM To: Murphy, Mike Subject: RE: 6131 Pacific Ave., Stockton Mike, you had said that VEW-7 was being used as to not draw water, but it was built into groundwater so that did not make sense to me. VEW-1 and VEW-6 are the only wells onsite not built into groundwater. Soil samples for analysis were apparently not collected during the drilling of VEW-1 (that was way before my time), but historically the highest concentrations of contaminants detected in soil were in samples collected near the west side of the former LIST area, specifically from VEW-2, B-3, GEO-2 and CPT boring SB-5. This is the area of the site where I think soil remediation should be focused. What concentrations are being detected in the influent vapor samples? How often are the samples being 9/27/2006