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�. City of Stockton o TL# 394-0192-01 t September 16, 1994 'I'r Page 13 :Ir ' Samples will be delivered to Twining's �cheiAstry laboratory in Fresno, California. Analytical methods with corresponding method detection limits and copies of the chain-of-custody records will be provided in the technical report. A-7 Laboratory Quality Assurance ualit :. Control (QA/OC)-: This section describes the laboratory QA/QC Procedures which will be followed during the analyses of the soil and groundwater samples by Twining's analytical chemistry laboratory,'. The QA/QC procedures will be developed to minimize outside interferences during analyses for each ;sample. The laboratory manager will be in charge of creating and aintaining 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; !# ■ Organic-free water will be monitoredIdai y for quality; ■ Gas chromatographs will be calibrate' dally; ■ Method blanks will be tested to check whether the glassware and reagents are free of interference from chemicals that would invalidate the analyses; and 'I I'f ■ Standards will be prepared using the applicable reference materials. ' Ifi 4 A-8 standard ORerating Procedures for Using Photoionization Detector(PID) and/or Drager® Tubes: The PID will be calibrated in accordance with the manufacture's recommendations prior to use in the field. Upon arrival p ri al at the project s.xte, ,the PID will be used to monitor concentrations background g r tions of, organic vapors in the atmosphere at the site. The background con'centrations will be 1 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 110. 0" on the PTD, subsequent readings of "0. 0" registered from samples tested in the field will be recorded as "ND" (not detected) . When background concentrations of organic vapors register at some quantity above 1101; 011 , �� subsequent readings +, registered from samples tested in the field at or below this value 1 will be recorded as "B/G" (background) . The Drager® tubes used will be consistent vithlthe type of analyte which is suspected as being present on the project site (i.e. for gasoline product use the benzene tube, for" diesel product use the petrol-hydrocarbon tube, etc. ) . i �,l