SITE INFORMATION AND CORRESPONDENCE

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Page 1 of 2 Ol . t Vicki McCartney [EH] From: Tim Cuellar[t uellar@advgeoenv.coml Sent: Wednesday, ugust 29, 2012 11:05 AM To: Vicki McCartn y [EH] Cc: Bill Little; Nue Henderson [EH]; greg@comfortairinc.com Subject: Comfort Air, 1307 Turnpike Rd., Stockton CA Attachments: Tables & Cal (App B) - ComAir Aquifer Pump Test- 0308.pdf, CA Figure 2 Site Plan.pdf; CA Figure 3 Geo Seciton AA'-w.pdf; CA Figure 5 Adsorbed TPH-g AA'-.pdf Vicki, AGE has reviewed furtlier the request within the EHD letter (dated 07/26/12) for the Comfort Air site. T e letter states that the EHD has reviewed the Corrective Action Plan (CAP) date 06/25/12, in which AGE concluded that high vacuum DPE was the most viable option to remediate the vadose zone, capillary fringe and upper saturated zone i.e. depths between 10' and 45' bsg). The CAP also recommended the installation of 2 DPE wells screened at depths between 10'- 30' (DPE-1) and between 25'-45' (DPE-2). However in the letter, the EHD stated that additional inform ion was needed to justify the proposed screen interval at depths between 25'-4E ', and that it was necessary to demonstrate to the EHD that draw-down will occur zt DPE-2 to de-water the well for actual dual phase extraction to occur. In accordance with your 07/26/12 letter, we would like to offer the following additional information or your consideration: • The core of hydrocarbon soil impact is located directly beneath the former UST area to de the of 45 feet bsg (see attached figure); the core of hydrocarbon dissolved impact appears to be located within the first hydrogeologic unit (i.e. between 17' and 50'). • Remediation veils W-1, W-2 and DPE-1 are proposed solely to address b� v� the core of hyc rocarbon-impact at depths between 10' and 30'. Initially, a ,35 DPE-stinger wi I be slowly lowered to within a few feet of the bottom of IS each well casing with the intent of completely de-watering each well and exposing a gre ter area to soil-vapor extraction. • Remediation v ell DPE-2 is proposed solely to address the significant hyd roca rbon-ir i pact at depths between 25-45'. Because it is anticipated that EW-1, EW-2 and DPE-1 will eventually dewater the UST area to depths of 30 feet bsg, then at a minimum, it is reasonable to expect that the screened portion in DPE-2 at depths between 25-30 feet bsg can be dewatered and exposed. • Based on an aquifer pump test conducted at the site in March 2008 (see attached), the ground water [eve[ at EW-1 was induced to a depth of 30 feet after 7 ho irs and at extraction rates between 2-3 GPM. Because the 8/29/2012