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City of Stockton A68104 01A October 25, 1995 Page A-6 laboratory in Fresno, California Analytical methods with corresponding method detection limits and copies of the chain-of-custody records are be provided in the technical report A-7 Laboratory Quality Assurance/Quality Control (OA/QC) This section describes the laboratory QA/QC procedures which are followed during the analyses of the soil and groundwater samples by Twining's analytical chemistry laboratory The QA/QC procedures are developed to minimize outside interferences during analyses for each sample The laboratory manager is in charge of creating and maintaining the program In general, QA/QC proposed for this investigation are summarized as follows ■ Analytical instruments are serviced on a regular basis to monitor accurate calibration, Y ■ Organic-free water is monitored daily for quality, ■ Gas chromatographs are calibrated daily, ■ Method blanks are tested to check whether the lassware and reagents are free of g interference from chemicals that would invalidate the analyses, and ■ Standards are prepared using the applicable reference materials A-8 Disposal of Rinsate and Soil Cuttings The soil cuttings generated by the drilling operations are sealed in 55-gallon United States Department of Transportation (DOT) �j approved steel drums The augers and sampling equipment are cleaned on racks and the rinsate subsequently be transferred to 55-gallon DOT approved steel drums The drums are temporarily stored on site at a location remote to the public Each drum is labelled to identify its contents The disposal of this material will be the responsibility of the client This material must be disposed of in accordance with all applicable Federal, State and Local regulations Cost of disposal of this material range from $65 00 to $100 00 a ton not including transportation and management fees A-9 Standard Operating Procedures for Using Photoianization Detector(PID) The PID is calibrated in accordance with the manufacture's recommendations prior to use in the field Upon arrival at the project site, the PID is used to monitor background concentrations of organic vapors in the atmosphere at the site The background concentrations are measured in a location upwind and removed as possible from sources of organic vapors on the site When background concentrations of organic vapors register as "0 0" on the PID, subsequent readings of "0 0" registered from samples tested in the field are recorded as "ND" (not detected) When background concentrations of organic vapors register at some quantity above "0 0", subsequent readings registered from samples tested in the field at or below this value are recorded as "B/G" (background)