Laserfiche WebLink
EDMUND G. BROWN JR. <br />GOVERNOR <br />C•111,01101• <br />Water Boards <br />Central Valley Regional Water Quality Control Board <br />MA T !NEW RODRIQUEZ <br />SECRETARY FOR <br />ENVIRONMENTAL PROTECTION <br />31 October 2016 <br />Mr. Steve Azevedo <br />West Clay Properties/Knife River Corporation <br />P.O. Box 6099 <br />Stockton, CA 95206 <br />Additional Site Assessment Work Plan - Addendum, West Clay Property, <br />639 West Clay Street, Stockton, San Joaquin County <br />California Regional Water Quality Control Board, Central Valley Region (Central Valley Water <br />Board) staff reviewed the Additional Site Assessment Work Plan - Addendum (Work Plan) dated <br />31 August 2016, and the third quarter 2016 groundwater monitoring report (3Q2016 Report) <br />dated 5 October 2016, both submitted on your behalf by Advanced GeoEnvironmental, Inc. <br />(AGE). The 3Q2016 Report was submitted with the title of "Groundwater Monitoring Report - <br />Second Quarter 2016", but presents the data for the third quarter 2016 groundwater monitoring <br />event. Staff have denied the submission in the State Water Resources Control Board's <br />Geotracker database and requested submission of an edited, correctly titled report. The West <br />Clay Property is located 639 West Clay Street in Stockton (Site). Staff concur with the scope of <br />work presented in the Work Plan, provided our comments, which follow later in this letter, are <br />adequately addressed. <br />Elevated concentrations of petroleum hydrocarbons continue to be detected in Site wells. <br />During the third quarter 2016, petroleum hydrocarbons were detected at maximum <br />concentrations of 8,600 micrograms per liter (ug/L) total petroleum hydrocarbons as gasoline <br />(TPH-G), 2,470 ug/L benzene, 29.1 ug/L methyl tert butyl ether (MTBE), and 1.8 ug/L <br />1,2-dichloroethane (1,2-DCA). The water quality objectives (WQ05) are 21 ug/L for TPH-G, <br />1 ug/L for benzene, 5 ug/L for MTBE, and 0.5 ug/L for 1,2-DCA. A 1,000-gallon gasoline UST <br />was removed in 1990, and based on the age, it was likely used to store leaded gasoline. <br />Groundwater pollution has not been adequately delineated laterally to the northeast of well <br />MW-29 or vertically near well MW-29; the scope of work presented in the Work Plan is designed <br />to addresses this data gap. Ozone injection was performed at the Site from 17 November 2006 <br />until fourth quarter 2010. Since shut-down of the ozone injection system, select monitored wells <br />show stable to decreasing trends, but many of the Site's monitoring wells have not been <br />sampled since before shut-down of the ozone injection system. Additional post remedial <br />monitoring is needed to establish trends and plume stability. <br />In the Work Plan, AGE proposes to install one (1) well, and to advance three (3) soil borings to <br />the northeast of well MW-29; this work is proposed to complete lateral and vertical delineation of <br />groundwater pollution. AGE proposes to collect depth discrete grab groundwater samples at <br />approximately 50 feet below ground surface (ft bgs), and at 85 ft bgs from the 3 soil borings. <br />AHL L. LuNuLt SD. P.E., PAMELA C. CILEVON P.E.. BCEE, LILHC .LC <br />11020 Sun Center Drive #200. Rancho Cordova. CA 95670 I www.waterboards.ca.govicentralvalley <br />RECYCLED PAPER