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• 0Memorand um CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD • CENTRAL VALLEY REGION 3443 Routier Road Phone: (916) 361-5600 Sacramento, CA 95827-3098 ATSS: 8-495-5600 TO: Antonia K. J. Vorster FROM: Gary A. Reents, P.E. Senior Engineer Project Engineer n L1 f� DATE: 8 December 1988 SIGNATURE: f J SUBJECT: GROUND WATER INVESTIGATION PROGRESS REPORT, SOUTHWEST HIDE COMPANY, SAN JOAQUIN COUNTY Moldenhauer Engineering Company (MEC) on behalf of Southwest Hide, submitted the subject report dated 11 October 1988. The report was supposed to contain descriptions and results of all of the work proposed in MEC' s June 1988 "Interim Report for Ground Water Study" , as revised by our 4 August 1988 comment memo- randum. However, not all of the proposed work was performed and the submitted information for the work that was performed is not complete. My specific specfic comments are as follows: 1. Insufficient work has been performed to identify and delineate ground water contamination sources. The report states that soil samples were collected and analyzed from seven boreholes near the ponds and all of the newly installed monitoring well boreholes. None of this data was included or discussed in the report. In addition, no actions were taken (as required by our 4 August memorandum) to definitively determine if the ponds are a source of ground water contamination or to identify potential source areas in the hide processing area. Work to define all sources needs to be completed as soon as possible, both to prevent further ground water contamination and to better identify the ground water plume or plumes. 2. Characterization of the hydrogeology is lacking. No logs or completion details for any of the new monitoring wells were included . In addition, no stratigraphic cross-sections or interpretations were orepared . No water level data was included in the report. The water level blot included in the report did not contain all the wells and was not correctly contoured . Piezometric surfaces are continous and cannot be segmented in-c areas as if they are not related . All in all , little has been presented to better describe the hydrogeologic setting for correlation and/or understanding of the contami- nation plume. Logs, cross-sections, and water level contours must all be prepared and interpreted to develop some conceptualization of the system. 3. The extent of the ground water contamination plume has not been completely defined either areally or N�ertically. The plume ;,,,s not been define d to the north, northeast, or around the ponds. The vertical extent of contamination has not been defined at any location,. Addition-,al )y, ground water contami- nation is primarily controlled by ground water r-,-;vetent which, in turn, is controlled by hydrology. As such, it ; s ver, important to have a good understanding or the stratigraphic and gradient controls at the site (refer toomment' ,22 abov ) A'ditional locations and screened intervals for monitori ny w= 11 s nezc to be proposed .