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]} EDw+uNo G.BRowN JR. <br /> ''-iL�q''e GOVERNOR <br /> C A I.1 E o R N I A MATTHE Y ORDRIOUEZ <br /> 61 <br /> WaterBoards ENVIRONMENTAL PROTECTION <br /> Central Valley Regional Water Quality Control Board <br /> 6 November 2018 <br /> Ms. Sharla Hardy Mr. Cyrus Youssefi <br /> City of Stockton — Public Works 601 Main Street Investors PTP <br /> 22 E Weber Avenue, Room 301 1006 Fourth Street, Suite 701 <br /> Stockton, CA 95202 Sacramento, CA 95814 <br /> SITE ASSESSMENT REPORT, MAIN STREET INVESTORS (AKA: CITY OF STOCKTON — <br /> MAIN STREET), 601 EAST MAIN STREET, STOCKTON, SAN JOAQUIN COUNTY <br /> Central Valley Regional Water Quality Control Board (Central Valley Water Board) staff <br /> reviewed the Additional Site Assessment Report (Assessment Report) dated 23 February 2018, <br /> submitted on behalf of the City of Stockton by Advanced GeoEnvironmental, Inc. (AGE). The <br /> Main Street Investors property, also known as City of Stockton — Main Street, is located at <br /> 601 East Main Street in Stockton (Site). <br /> In October 2017, AGE installed two (2) soil vapor wells, VP-1 and VP-2, and two (2) <br /> groundwater monitoring wells, MW-1 and MW-2. A third monitoring well was proposed, but <br /> could not be installed due to overhead access restrictions. Soil gas wells were advanced to 8.5 <br /> feet below ground surface (ft bgs) with a vapor tip installed from 7.8 to 8.0 ft bgs. The <br /> groundwater monitoring wells were screened from 20 to 40 ft bgs. AGE detected <br /> 190 micrograms per liter (ug/L) total petroleum hydrocarbons as gasoline (TPH-G), 1,600 ug/L <br /> TPH as diesel (TPH-D), and 1.8 ug/L total xylenes in groundwater from well MW-1. Petroleum <br /> hydrocarbons were not detected in the groundwater sample from well MW-2. AGE detected up <br /> to 8.8 micrograms per cubic meter (ug/m3) benzene, and 15 ug/m3 tetrachloroethene (PCE) in <br /> soil gas samples. <br /> Central Valley Water Board staff have the following comments: <br /> 1. A second soil gas sampling event should be performed to confirm results. Please <br /> submit a soil gas sampling report by 30 March 2019. <br /> 2. Installation of a third groundwater monitoring well is needed to define the down-gradient <br /> extent of the release, and to allow for calculation of groundwater flow direction and <br /> gradient. AGE evaluated nearby environmental sites and reported an anticipated flow <br /> direction towards the northeast. By 31 January 2019, please submit a Work Plan <br /> presenting a scope of work for installation of at least one additional shallow screened <br /> well to the northeast of MW-1. <br /> KARL E. LONGLEY SCD, P.E., CHAIR I PATRICK PULUPA, ESO., EXECUTIVE OFFICER <br /> 11020 Sun Center Drive#200,Rancho Cordova,CA 95670 I www.waterboards.ca.gov/centralvalley <br /> C'j RECYCLED PAPER <br />