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FROM : Central Ualleg RWQCB TEL: 316 255 3052 JUL. 7.1995 2:16 FM P 3 MEMORANDUM CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD • CENTRAL.VALLEY REGION 3443 Routier Road, Suite A Phone: (916)2553000 Sacramento,CA 95627-31)90 CALNET:5.494-3000 To: Karen Bessette From: Robert Reeves Project ManagerGcologis ^) DATE: 6luly 1995 SIGNATUR Subject: IRRIGATION WFLL INSTALI.ATIONAT 26101 S. CHRISHAN ROAD NF_4R DFFFNSE DISTRIRVTION RF.G70N WEST(DDRW] TRACY,SAN JOAQUIN COUNTY. I have reviewed a letter by Dennis C.Noble,representing Anthony Trainas,requesting that we review a permit for construction of an irrigation well at 26101 S. Chrisman Road. It is my understanding that the Trainas wish to construct an irrigation well thal would pu np approximately 250 gallons per minute (gpm)at a depth of 160 feet below ground surface(BGS). The irrigation well will be used to drip irrigate a 10 acre parcel bordering the western perimeter of DDRW Tracy. My roview focused on determining if the proposed irrigation well could affect the proposed remedial design or the contaminant plume(PCE and'I'CL plume)at DDRW Tracy. I reviewed the following technical documents: Pre-Design Data Report for Operable Unit 1, February 1995(Sections 1,2,3 and Attachments A and 13) • Well Monitoring Program Quarterly Monitoring Report,October 1994 Sampling Round Well Monitoring Program Quarterly Monitoring Report, August 1994 Sampling Round Background: Tracy has identified four hydrostrafigraphic units in the Upper Tulare Member of the Tulare Fonnation': the Above Upper Horizon(0 to 25 feet BGS),the Upper Horizon(25 to 60 feet BGS),the Middle Iforizon (75 to 105 feet BGS)and fit Lower Horizon(I 10 to 170 feet BG), The Corcoran Clay is found at 220 feet BGS and is the regional confining pryer between the Upper Tulare Member and the Lower Tulare Member of the Tulare Formation. Isopach maps presented in the Pre-Design Report(February 1995), show several well-defined palcochannel deposits in the Upper Horizon and Middle Horizon.Although the isopach maps do not extend west of DDRW Tracy, it is likely that the palcochannel deposits found beneath DDRW Tracy also extend beneath the subject property. Geologic cross section-.,,,how four well defined water hearing zonce that also extend beneath the subject property and are present at depths ranging from 25 to 170 feet BGS.