FIELD DOCUMENTS - Laserfiche WebLink

Home Browse Search

e Quik Stop Station No. 76 March 18,2009 Stockton,California Soil Gas Investtigation Work Plan Task 1 Retain a C57-licensed drilling and mobile laboratory contractor experienced in soil gas investigations; obtain permits, if required, from the local regulatory agency; notify Underground Services Alert (USA) for identification of underground utilities in the immediate Site area; update the Site-specific Health and Safety Plan to include soil gas investigation work. Task 2 Advance temporary soil gas sampling probes (SG-1 through SG-5) to depths '1 of 5 to 6 feet below surface grade (bsg); utilize hydrated bentonite to seal the ground surface around the drive rod to prevent ambient air intrusion from occurring; subsequent to sampling, abandon all borings by backfilling with bentonite/cement grout; finish the surface with a flush concrete plug. Advance the initial soil gas probe at the location that is likely to yield the highest constituent concentrations; at all sampling points, allow 26inutes o elapse after the sampling probe is landed, opened, flow tested at the target depth and the surface is sealed for subsurface conditions to equilibrate prior I to collecting soil gas samples; steadily draw soil gas samples into new 50 ml C: ✓� sampling syringes over at least 15 seconds. Conduct purge volume test at the initial soil gas sampling point for evaluation all of the appropriate purge volume for the remaining locations; evaluate purge volume for the sampling apparatus tthati cl des the annular space around the open sample probe and the sample tubing�c o'nduct purge volume tests of 1; 3 and 7 apparatus volumes; purge and sample at flow rates less than 200 4i milliliters per minute lmllmm); abort sampling if maximum attainable flow rates are less than I O ml/qn or vacuum exceeds 10 inches of mercury; select the purge volume that provides the sample that contains the highest constituent concentrations; if two or more purge test samples contain similar concentrations, purge 3 volumes prior to collecting each sample. Conduct leak testing at each sampling location utilizing 1,1-difluoroethane (DFA) as tracer compound; dispense leak test compound at any location along the sampling apparatus where ambient air could enter the sample flow; if tracer compound is detected, evaluate the cause of the leak and correct before continuation of sampling; collect one field blank and one duplicate sample to check for procedural and analytical reproducibility/precision, respectively; analyze blank and duplicate samples utilizing the same methods as field samples. -ru- Y14t (r cl Analyze soil gas samples in the mobile lab within 30 minutes of collection for: total petroleum hydrocarbons as gasoline (TPHg), the volatile aromatic compounds benzene, toluene, ethylbenzene, total xylenes (BTEX), the fuel oxygenate methyl-t-butyl ether (MTBE) and for the leak compound DFA-by EPA Method 8260B; utilize analytical reporting limits at or below the values for the selected analytes as listed in the shallow soil gas Table 2 of California 5GI WP Mar09 Project No.7076.15 3 HORIZON ENVIRONMENTAL INC.