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-A • MEMORANDUM . CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD • CENTRAL VALLEY REGION 3443 Routier Road, Suite A Phone: (916) 255-3000 Sacramento, CA 95827-3098 CALNET: 8-494-3000 TO: Antonia K.J. Vorster FROM: Cori Condon Senior WRC Engineer Assoc. Engineering Geologist DATE: 23 March 1994 SIGNATURE: SUBJECT: SITE INSPECTION AND MEETING, MARLEY COOLING TOWER COMPANY, STOCKTON, SAN JOAQUIN COUNTY On 10 November 1993 I did a site inspection of the Marley Cooling Tower Company's Stockton facility. The purpose of this meeting was to clarify the sampling objectives set forth in the newly adopted NPDES permit no. 93-221, adopted by the Board on 22 October 1993. The inspection was preceeded with a meeting at which Mr. David Bates presented a letter from GeoAnalytical Laboratories stating that arsenic analyzed by EPA Method 206.2, using graphite furnace is the preferred method of analysis for arsenic, as opposed to the method 206.3 hydride generation specified in the NPDES permit. As both of these methods will produce results within acceptable detection limits, either of the methods will be acceptable. The second issue discussed pertained to evaluation of the total dissolved solids from the treatment plant. The permit specifies that influent samples shall be collected from the flow equalization basin and the influent holding tank. The permit further specifies that these samples shall be combined into a single sample which is representative of the volume and nature of the inflow to the plant. The influent sample is to be collected at approximately the same time as the effluent so that the increase in TDS from the treatment system can be monitored. The influent and the effluent samples are to be weekly composite samples. Marley has been collecting a grab sample from each system on the influent in order to comply with the permit requirement of taking the influent and effluent samples at approximately the same time. In addition to this set of samples, a weekly composite sample is being collectd on the effluent to satisfy the effluent monitoring requirement. At the present, the treatment systems are not equipped to collect composite samples on the influent lines. In the meeting Marley proposed to move the composite sampler formerly on one of the effluent streams and setting it up on one of the influent streams and purchasing the necessary equipment to conduct composite sampling on the remaining influent line. This way a composite of the weekly ion exchange influent, a weekly composite on the andco influent and a weekly composite on the combined effluent will be collected. This will deviate from the permit in that the influent samples will not be combined however, it will meet the intentions of the permit to evaluate the change in concentration of TDS from the treatment system and what the total concentration is being discharged in the Stockton Diverting Canal, and is therefore acceptable. Marley will be reporting the volume of flow through the ion exchange, the volume of flow through the andco system and total flow processed. Flow through each system is being recorded in order to weight the concentration of the effluent if necessary. The system generally processes approximately half of the contaminated water through the andco system and half through the ion exchange system.