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v` Eowl G.BROW JR. eorm�s 0 CALIIOW51A d=FWTAMa7111 Pff FOR OUO4uFi Water Boards Central Valley Regional Water Quality Control Board 10 February 2014 Leon Marineau Christian L'Orange Cascades Inc. Drinker Biddle & Reath LLP 471 Marie-Victorin 50 Fremont Street Kingsey Falls, Quebec, Canada JOA 180 San Francisco, CA 94105 DOPACO, INC., 800 WEST CHURCH STREET, STOCKTON, SAN JOAQUIN COUNTY REGIONAL BOARD CASE 391187 California Regional Water Quality Control Board, Central Valley Region (Central Valley Water Board) staff reviewed the Work Plan to Install Groundwater Monitoring Well DMW-5B (Work Plan). The Work Plan was received 30 January 2014, and submitted by Geosyntec Consultants (GC) for Cascades, Inc. for the Dopaco, Inc. (Case 1). In the Work Plan GC proposes installation of one deep monitoring well DMW-5B in the toluene source area to complete vertical delineation and to confirm previous groundwater impacts reported down to 85 feet below ground surface (' bgs). DMW-5B will be installed after the corrective action excavation of soil down to 30' bgs. is proposed to be installed DMW-5B will be constructed with a 50' conductor casing, , advanced through the backfill consisting of clean compacted soil and screened from 65' to 75' bgs. After advancing the conductor casing through the excavation fill material, soil will be logged in the boring at 5' intervals from surface down to 50' bgs and continuously logged from 50' to total depth of the boring at 75' bgs. We concur with the activities proposed by GC in the Work Plan with conditions as detailed below. We are aware Dopaco has been ordered to conduct investigation and cleanup of toluene, and any chemicals commingled with toluene, from the property at 800 West Church Street in Stockton by agreements specified in the Stipulated Injunction and Consent Decree per United States District Court, Eastern District of California Case 2:08-cv-02623-GEB-DAD, dated 20 April 2012. We concur with the activities proposed by GC in the Work Plan with the following conditions: 1. A shallow monitoring well should be installed near DMW-5B, to monitor the sand zone, indicated at 40' bgs in the CPT-13 logs. This sand zone is currently monitored by three existing monitoring wells to the east, west and south. The shallow well will confirm the effectiveness of the corrective action, provide the necessary monitoring data to show a declining trend in the groundwater pollution, and provide additional information on groundwater gradient and direction of groundwater flow in the sand zone. As an additional benefit, the shallow well should be capable of extraction of groundwater, if necessary. 2. Additional investigation consisting of monitoring wells to the north across Church Street is also necessary to confirm whether the groundwater plume is migrating and to confirm the downgradient extent of the groundwater plume. The off-site zones to be monitored may be adjusted after initial monitoring data is received from DMW-5B. We suggest that DMW-5B be sampled and analyzed by an onsite lab to provide a fast turn-around, so the drilling of the additional wells can be accomplished with a single mobilization. K#j%L E.LORaLer ScD,P.E.,amm r PAMetA C.CRm66N P.E.,SCEE,memunwe OFFICER 17026 SUR C—sm Qhs 11206,Ruldw Conkm CA 9WF I WWW.WaWb0WCh.0L9=Osntrslvs0s/ Q RGCYCLSO PAPNR