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' CPA0057 Sites -3 - RECL-NED 27 April 2016 West Charter Way and Lincoln Street Stockton, San Joaquin County MAY 0 "1 2016 ENVIRONMENTAL HEALTH DEPARTMENT Comments on this project follow: 1. Central Valley Water Board staff concur with the remedial strategy proposed by Stantec on the condition that, additional ART wells are installed east of SMW-11 and SMW-26B to address elevated levels of benzene detected in SMW-11 at 471 ug/L at 122 ft. bgs and in SMW-26B at 1,000 ug/L at 50 ft. bgs. Please confirm the addition of ART wells in the northeast portion of the former Texaco (Shell) property in a Work Plan Addendum due by 30 June 2016. 2. The installation and operation of the SVE /AS wells and ACT wells are proposed to cleanup soils and groundwater impacted by the commingled plume properties. Because this may be the final cleanup action conducted at this Site, it is appropriate to conduct public notification of the proposed actions and site conditions. Therefore, by 29 July 2014, please submit a draft Fact Sheet summarizing the remedial investigation and the corrective action proposed. In addition, please provide a list of names and addresses of the property owners and residents to be notified within 500 feet of the contaminant plume. The distribution list must also include the following: municipal and county water districts, water replenishment districts, special act districts with groundwater management authority, agencies with authority to issue building permits for land affected by the petroleum release, owners and occupants of the property impacted by the petroleum release, the owners and occupants of all parcels adjacent to the impacted property(ies), and this office. An example draft Fact Sheet is attached and an electronic copy was emailed to your consultant, Stantec, on 27 April 2016. A Fact Sheet figure will need to be included with the draft Fact Sheet for our review, and must show the subject site, the estimated extent of the groundwater pollution, and the adjacent properties. We can work with you and your consultant, through email to provide edits of the draft Fact Sheet, figure, and distribution list. 3. Public notification of the proposed activities must be conducted to allow the public an opportunity to ask questions and provide comments. Please prepare a draft Fact Sheet and distribution list of owners and occupants within 500 feet of the know groundwater pollution 4. The State Water Board Low Threat Closure Policy requires delineation of the contaminant plume to water quality objectives (WQOs). The WQO for benzene is 1 ug/L. Even with the proposal to install monitoring wells SMW-31 B, SMW-32B, SMW-33B, SMW-35D, SMW-36D, and SMW-34E, delineation of the horizontal and vertical extent of petroleum impacts is still needed in the following areas; a. North and east of A zone wells AMW-1 and AMW-2 (benzene detected at 1,000 and 6,200 ug/L respectively in October 2015) and southwest of well CMW-5A (detected at 519 ug/L benzene when last sampled April 2015). Gradients in the A zone are reported to be predominantly to the east-southeast, as well as to the north-northeast. Please propose to collect a series of depth discrete grab ground water samples to the north and east of the ARC property to complete delineation of petroleum impacts.