SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

i Eoemmo G BRowu JE 077 Mn..Raw Rooniguaz Water Boards Central Valley Regional Water Quality Control Board �ELeEY�� I� D 18 July 2016 JUL 11 1016 David Vossler EWIRONPIENTAL HEALTH GHD Inc. PERMIDSERyICES 3831 N. Freeway Blvd #220 Sacramento, CA 95834 DOCUMENT REVIEW, SIEBOLD CONSTRUCTION, 820 S. AMERICAN STREET, STOCKTON, SAN JOAQUIN COUNTY (RB CASE # 390394) On behalf of the Central Valley Regional Water Quality Control Board (Central Valley Water Board), I would like to inform you that as of 1 June 2016, 1 am the assigned caseworker for the above referenced site. My contact information is included at the end of this letter. I have reviewed the Additional Subsurface Investigation Report and 3rd Quarter 2015 Groundwater Monitoring and Sampling Report dated 30 November 2015 (Report), submitted by GHD Inc. (GHD). This Report details the installation of three (3) shallow monitoring wells (MW-5 through MW-7), and one (1)deep monitoring well (MW-8). Wells MW-5 through MW- 7 were screened between 22 and 37 feet below ground surface (bgs), and were intended for the purpose of downgradient delineation of the hydrocarbon groundwater plume. During the sampling event on 27 August 2015, samples collected from all three of these wells were non- detect for all analyzed constituents, and thus lateral delineation in the shallow zone (22 to 50 feet logs) is complete. MW-8 was screened between 65 and 75 feet bgs, and was intended for the purpose of vertical delineation of groundwater pollution. The August 2015 sample collected from this well contained total petroleum hydrocarbons as gasoline (TPHg), benzene, and MTBE at concentrations of 230 ug/L, 23 ug/L, and 3.5 ug/L, respectively. Concentrations for TPHg and benzene were reported above Water Quality Objectives of 1 ug/L and 5 ug/L, respectively. In the Report, GHD recommends that deep well MW-8 be sampled quarterly for one (1) hydrologic cycle (4 quarterly samples) for the purpose of establishing groundwater contaminant trends in this well. Based on groundwater data to be collected from MW-8, GHD intends to either install additional deep wells or evaluate the Site for closure. I concur with this recommendation. Please perform third quarter 2016 groundwater monitoring and sampling and submit a Semi-Annual Groundwater Monitoring Report by 30 October 2016. Please continue to perform semi-annual groundwater monitoring and sampling during first and third quarters until No Further Action is granted, and submit reports within 30 days of the end of the applicable quarter. KARL E. LONGLEY SOD, P.E.,CHAIR I PAMELA C. CREEOON P.E., BCEE,EXECUTIVE OFFICER 11020 Sun Center Drlve#200.Rancho Cordova,CA 95670 1 www.waterboards.ca.gov/Centralvalt.y C"aacrcreo FAIIII