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• MEMORANDUM • <br /> CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD - CENTRAL VALLEY REGION <br /> 3443 Routier Road, Suite A Phone: (916) 361-5600 <br /> Sacramento, CA 95827-3098 np ATSS Phone: 8-495-5600 <br /> TO: Antonia K. J. VorsterLl FROM: Camilla Williams <br /> Senior WRC Engineer 111111 ��1��1 Engineering Geologist <br /> DATE: 31 January 1991 SIGNATURE: <br /> SUBJECT: DESIGN DOCUMENTS FOR THE SUBSURFACE SOIL FLUSHING SYSTEM AND THE GROUND WATER <br /> COLLECTION SYSTEM, MARLEY COOLING TONER COMPANY, SAN JOAQUIN COUNTY <br /> I have reviewed the design documents for Subsurface Soil Flushing System arid the Ground <br /> Water Collection System submitted on 3 December 1990 by Black and Veatch for the Marley <br /> Cooling Tower Company (MCTC) . On 14 January 1991, Jim Austreng, of the Department of <br /> Health Services, and I met with representatives of MCTC to discuss our preliminary <br /> review of the documents and to conduct an inspection of the site. The report of the <br /> inspection is attached. <br /> I have relatively few comments on the documents. However, I do have two major concerns <br /> and other comments on the plans for these systems which are discussed below. Marley <br /> should consider these concerns and comments prior to the installation of the subsurface <br /> soil flushing system and the ground water collection system. <br /> MAJOR CONCERNS <br /> 1 . The documents for the Subsurface Soil Flushing System call for soil samples to be <br /> collected every five feet. The samples are to be analyzed for arsenic, copper, <br /> total chromium and hexavalent chromium. It is my understanding that the soil <br /> samples are to be collected and analyzed as a preliminary characterization which <br /> will presumably be used as a baseline for the soil flushing and to use for future <br /> decisions (in five years) regarding closure of the upper 20 feet of the unsaturated <br /> zone. However, the documents do not propose to analyze the samples for pH, <br /> electrical conductivity (EC) or total dissolved solids (TDS) and do not specify <br /> whether the samples will be analyzed for total concentrations or soluble <br /> concentrations. <br /> If the intent of the soil sampling and analyses is to characterize the unsaturated <br /> zone, then pH, EC and TDS should be included in the list of analytes. The <br /> concentrations of these constituents are important because elevated concentrations <br /> may indicate potential contamination by other residual waste constituents. <br /> Although total concentrations are needed to perform a health based risk analysis, <br /> soluble concentrations are needed to determine the potential threat to water <br /> quality posed by the residual waste constituents and the effectiveness of soil <br /> flushing. Therefore, I recommend that all of the soil samples be analyzed for <br /> soluble concentrations of arsenic, copper, total chromium, hexavalent chromium, pH, <br /> EC and TDS. <br /> 2. The design documents call for the monitoring tubes to be installed ten feet below <br /> the current ground water table, to install the injection wells ten feet above the <br /> current ground water table and to install the extraction well with 30 feet of <br /> screen. My concern with these proposals is that the designs may not be flexible <br />