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Weldon Church Site Background Information Page 8 of 12 with a photo-ionization detector (PID) was used to monitor V-1 through V-3. Following Purging and organic vapor monitoring, soil-vapor samples were collected from V-1 through V-3 using Tedlar bags. After samples were collected, sample bags were sealed, labeled, logged on a chain of custody form, and placed into a dry cooler(room temperature). Vapor points V-4 and V-5 contained water and subsequently were not sampled. Organic vapor was detected from V-1 through V-3 at concentrations of 145 parts per million volume (ppmv), 1,513 ppmv, and 1,000 ppmv, respectively. TPH-g were detected in soil-vapor samples V71 through V-3 at concentrations ranging between 3,000 1-19/1 (V-1)and 400,000 1-19/1 (V-3). BTEX compounds were detected in the same samples at maximum concentrations of 240 pg/I benzene, 950 pg/I toluene, 240 pg/I ethylbenzene and 950 pg/I total xylenes (V-3). HUMAN HEALTH RISK ASSESSMENT Using a version of the Johnson and Ettinger Model, a Tier 2 Human Health Risk Assessment was performed for inhalation of indoor air at 104 West Beverly Place, Trac CA. The HHRA was performed to assess the cancer risk and hazard index for va or intrusion of benzene. The maximum benzene concentration 240 p soil-vapor samples collected on 09 March 2011 was used for the mold I The benzene concentration used for the model is the highest concentration of benzene in soil-vapor detected at the site. The Johnson and Ettinger Model calculated the cancer risk at 0.000000743 and the hazard index at 0.0373. AIR SAMPLING MAY 2011 One passive integrated air sample was collected from the crawl space (Crawl Space-1 beneath the residence at 104 West Beverly Place, Tracy, CA. Additionally, ) passive integrated ambient air samples were collected from the southwest (Ambient-SW) and southeast (Ambient-SE) area of the backyard at 104 West Beverly Place, Tracy, CA. Air samples were collected using six-liter Summa canisters. The sampling inlet on each canister was connected to a mass flow controller containing a particulate filter; the flow controllers were calibrated to flow rates between 3.37 milliliters/minute (ml/min) and 3.49 ml/min in order to collect air samples over a 24-hour period. Each canister's initial vacuum was measured and recorded to ensure the initial vacuum was greater than 25 inches of mercury (in/Hg); Initial vacuum's were measured between sample collection. 28.5 and 29.5 in/Hg prior to air For Crawl Space-1, polypropylene tubing (PPE)was connected to the mass flow controller inlet and inserted horizontally through 0.5-inch diameter polyvinyl chloride (PVC) conduit Advanced CeoEnvironmental,Inc.