WORK PLANS - Laserfiche WebLink

Home Browse Search

r 3.2 Soil Vapor Sampling and Analysis To evaluate potential soil vapor concentrations at the site, Ramage Environmental will collect soil vapor samples according to the California Regional Water Quality Control Board Los Angeles .r Region, Interim Guidance for Active Soil Gas Investigation dated February 25, 1997; the California Department of Toxic Substances Control Advisory—Active Soil Gas Investigations dated January 28, 2003; and the California Department of Toxic Substances Control Interim Final Guidance for the Evaluation and Mitigation of Subsurface Vapor Intrusion to Indoor Air, dated December 14, 2004 and revised February 7, 2005. _ To optimize detecting and delineating the extent of hydrocarbon vapors in soil, Ramage Environmental will supervise the collection of soil vapor samples from five on-site locations. As shown on Figure 3, the soil vapor samples will be collected near the south end of the former UST, along the base of the Courthouse building, and northeast (i.e., downgradient) of the former UST. V A C-57 licensed drilling contractor (i.e., driller)will collect the soil vapor samples by advancing shallow borings to approximately five-feet bgs using portable direct-push sampling equipment. The driller will thread a retractable vapor sampling probe tip connected to 1/8-inch diameter Teflono tubing through the center section of the direct-push rods. When the sampling probe reaches the specified sampling depth, the driller will retract the outer sleeve to expose a 3-inch screen section for soil vapor extraction. To allow for subsurface equilibrium, the driller will wait at w least 20-minutes after probe installation to sample. Prior to sampling, the driller will purge the vapor well using an air sampling pump for approximately five minutes to evacuate the casing and to draw soil vapors from the surrounding formation. The driller will collect the soil vapor samples through the tubing into laboratory- supplied Surra®canisters with a rated purge rate less than 200 milliliters per minute. The driller will use dedicated and disposable tubing for each soil vapor probe boring, and will properly decontaminate all sampling equipment between vapor points The soil vapor samples will be properly packaged, and transported with chain-of-custody documentation to a state of California-certified hazardous waste testing laboratory for analysis. •� The laboratory will analyze the soil vapor samples on a standard turn around time for TPH-as- gasoline, BTEX, and MTBE by EPA Methods 8021 B/8015M and 8260B. ..r 10 w