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EDMUND G. BROWN JR. <br />GOVERNOR <br />RIA <br />Water Boards <br />Central Valley Regional Water Quality Control Board <br />MATTHEW RODRIOTTEZ <br />SECRETARY FOR <br />ENVIRONMENTAL PROTECTION <br />25 July 2017 <br />David Vossler <br />GHD Inc. <br />3831 N. Freeway Blvd #220 <br />Sacramento, CA 95834 <br />SIEBOLD CONSTRUCTION, 820 S. AMERICAN STREET, STOCKTON, SAN JOAQUIN <br />COUNTY, CASE # 390394 <br />Central Valley Regional Water Quality Control Board (Central Valley Water Board) staff <br />reviewed the 2 ' Quarter 2017— Semi-Annual Groundwater Monitoring Report and Site Closure <br />Request (2Q17 Report) dated 20 July 2017, submitted on your behalf by GHD Inc. (GHD) for <br />the Siebold Construction property located at 820 South American Street in Stockton (Site). In <br />the 2Q17 Report, GHD indicates that the Site meets closure criteria as established in the State <br />Water Resources Control Board's Low Threat Underground Storage Tank Case Closure Policy <br />(LTCP), and recommends closure. <br />Central Valley Water Board staff have the following comments on the current status of the <br />assessment and cleanup of the petroleum release from the Site: <br />1. The Site meets all eight (8) of the LTCP General Criteria. <br />The Site is in the service of a public water system [California Water Service (Cal <br />Water)]. <br />The release consists only of petroleum. <br />The primary release has been stopped by underground storage tank (UST) <br />removal. <br />There is no free product. <br />A Site Conceptual Model was included as part of the 2Q17 Report. <br />Secondary source has been removed to the extent practicable. Limited over- <br />excavation was performed in the vicinity of the former 8,000-gallon UST, though <br />as the tank removal report has not been located, the extent or volume of the <br />excavation is not known. <br />Soil and groundwater have been tested for methyl tert butyl ether (MTBE). <br />No nuisance exists as defined by Water Code 13050. <br />2. Since 1997, Siebold has installed a total of eight (8) monitoring wells and one has <br />destroyed one monitoring well at the Site. Depth to water at the Site most recently (June <br />2017) ranged from 22.90 to 24.52 feet below ground surface (bgs), and groundwater <br />elevation ranged from 5.63 to 6.24 feet below mean sea level. Since 2011, groundwater <br />flow has ranged from north to east-northeast, with east-northeast being the predominant <br />KARL E. LONGLEY ScD, P.E., CHAIR I PAMELA C. CREEDON P.E., BCEE, EXECUTIVE OFFICER <br />11020 Sun Center Drive #200. Rancho Cordova, CA 95670 I www.waterboards.ca.govicentralvalley <br />C:, RECYCLED PAPER