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Page 6 of 15 <br /> Mike, <br /> From: Josh Ewert [mailto•ewertColgeoconinc com] <br /> Sent: Friday, November 04, 20114:27 PM <br /> To: Mike Infurna [EH] <br /> Subject: RE: 5400 and 5606 Pacific Avenue, Stockton -Well Destruction <br /> Information <br /> Good Afternoon Mike, <br /> Thank you for your comments on our proposal to destroy these 89 wells in <br /> Stockton. Now that finally have some time to spend on this job again, I will <br /> proceed accordingly. However, I'd like to make a case that some of the wells you <br /> proposed to be completely overdrilled should be allowed to be pressure grouted. <br /> ? VEW-16,VEW-19 and VEW-22—You state that these wells are to be <br /> drilled out based on their location within a line of estimated residual <br /> contamination and because VEW-19 and VEW-22 had soil vapor hits. The <br /> line that you reference is an isoconcentration contour for residual TPHg <br /> in groundwater from AECOM's 9-22-2011 Figure 11. However,these <br /> wells do not and have never extended into groundwater making them <br /> not applicable to groundwater isocons.Additionally,the field data sheets <br /> presented in Attachment D of AECOM's Quarterly Remediation Status <br /> Report for the Fourth Quarter of 2009 show that each of these wells had <br /> PID readings of 0.0 immediately before the system was turned off for <br /> good on 12-28-09. This represents the most recent vapor data that we <br /> have for these wells and it shows that these wells are not in an area of <br /> pollution or contamination. <br /> ? MW-16 and MW-32—You state that these wells are within areas of <br /> contamination as shown on AECOM's 9-22-10 Figures 14 and 15.Are you <br /> willing to reconsider this due to the fact that these data points are <br /> estimated results?Or in the case of MW-32,the estimated result of 0.6 <br /> pg/1 is below its ESL, MCL and WQO and thereby doesn't fit the county's <br /> definition of contamination or pollution? <br /> ? AS-20 and AS-21—You state that these wells are to be drilled out based <br /> on their 2008 soil data and because they are within the isoconcentration <br /> line shown in AECOM's 9-22-2010 Figure 11.The soil samples for AS-20 <br /> reported TPHg concentrations at a depth of 50 to 70 feet with non-detect <br /> results at 80 and 90 feet while soil samples for AS-21 reported a TPHg <br /> concentration at 55 feet with non detect results at 65 and 75 feet.This <br /> suggests that the contaminated soil interval is from 50 to 70 feet. I would <br /> argue that well MW-4 shows this interval is now clean because 1)the <br /> well is screened through this specific interval (48 to 68 feet) 2) it is <br /> directly adjacent to the AS-20 and AS-21 and 3) it has reported remained <br /> completely non-detect for twelve of the last thirteen monitoring events. <br /> ? AS-14,AS-15,AS-17, AS-18,AS-20 and AS-21—I think some special <br /> consideration should be given before requiring the overdrilling of these <br /> 1-inch wells.There is a high probability that your 15-inch auger Plan B <br /> scenario would come into play on these 1-inch wells but even that <br /> scenario isn't failsafe. Having talked to two drilling companies about this, <br /> 12/20/2011 <br />