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_ Euuuxu O.Bxvnx Jx. <br /> �s -- eortxnoe <br /> aCAnART R0Aoawuez <br /> [xalppNM Writ PROiECIIGN <br /> Water Boards <br /> Central Valley Regional Water Quality Control Board . a '''°''T 7,. F <br /> SEP 18 20% <br /> Mr. Mark Buller 17 September 2014 <br /> 1137 South Stockton Street <br /> Stockton, CA 95206 <br /> GROUNDWATER MONITORING REPORT—SECOND QUARTER 2014, IDEALEASE, <br /> 1137 SOUTH STOCKTON STREET, STOCKTON, SAN JOAQUIN COUNTY <br /> California Regional Water Quality Control Board, Central Valley Region (Central Valley Water <br /> Board) staff reviewed the 7 May 2014 Groundwater Monitoring Report—Second Quarter 2014 <br /> (Report) submitted by Advanced GeoEnvironmental, Inc. on behalf of Idealease for the property <br /> at 1137 South Stockton Street in Stockton (Site). The Site consists of an office building;truck <br /> wash facility; fuel dispenser area; and one 12,000-gallon diesel aboveground storage tank <br /> (AGT). The Site is paved with asphalt and concrete and a canopy covers the truck wash and <br /> dispenser areas. <br /> The Report summarizes the April 2014 groundwater monitoring event and recommends that <br /> "...the site be considered for closure as a low-threat groundwater case." Depth to groundwater <br /> was about 15 feet below ground surface (bgs) and flow is radially toward a groundwater <br /> depression centered at MW-4, which was the only well with detections of petroleum <br /> hydrocarbons and contained total petroleum hydrocarbons as diesel (TPHd) at 140 micrograms <br /> per liter (Ng/L). Although the case meets Groundwater-Specific Criterion No. 1 of the State <br /> Water Resources Control Board's Low-Threat Underground Storage Tank Case Closure Policy <br /> (LTCP), which may be used for closure evaluation of AGT cases, it does not meet other <br /> required criteria of the LTCP, as discussed in our comments below. <br /> Our comments are: <br /> 1. Central Valley Water Board staff reviewed the historical groundwater concentrations to <br /> assess whether the Site was a candidate for low risk closure. Groundwater <br /> concentrations are declining and in April 2014 only one well contained concentrations <br /> above the water quality objectives (WQOs). Based on the recent groundwater <br /> monitoring results, Board staff concurs that remaining groundwater concentrations meet <br /> the LTCP for the groundwater-specific criteria. <br /> 2. Remaining soil concentrations exceed the California Regional Water Quality Control <br /> Board— Bay Area Region Environmental Screening Levels (ESLs) for gross <br /> contamination and, therefore, Central Valley Water Board staff does not concur the Site <br /> qualifies for closure under the LTCP. The majority of the remaining mass of TPHd in soil <br /> is at four to six feet bgs and could be encountered by construction workers excavating in <br /> the area. As stated in AGE's No Further Action Required(NFAR) Report dated 9 August <br /> 2013, more than 10% of the confirmation samples obtained from the excavation <br /> exceeded the ESLs for gross contamination. The soil samples collected from the <br /> excavation near the dispenser islands (Area A) contained maximum TPHd <br /> KARL E. LONGLEY Soo. P.E.,GIMVI I PAMELA C. CREEOON P.E., RCEE,CXECUTIVC Ornom <br /> 11020 Sun Center Drive#200,Rancho Cordova,CA 96670 I www.waterb rda.ca.Bov/Centmlvelley <br /> 4J nemc[eo rnven <br />