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of benzene, toluene, ethyl benzene, and total xylenes (BTEX) constituents or a total of estimate <br /> of 6,260.15 pounds of vapor phase hydrocarbons. Using an average density of gasoline of 6.25 <br /> pounds per gallon, this represents removal of the equivalent of approximately 1,000 gallons of <br /> gasoline. <br /> SCOPE OF WORK <br /> Planning <br /> ATC will schedule field personnel and equipment, notify Underground Services Alert to locate <br /> underground utilities as required, and perform other necessary field preparation and job start-up <br /> activities. A private utility locating service may also be used to locate underground utilities that <br /> may be present in the work areas. <br /> Installation of Soil Gas Sampling Probes <br /> This task includes mobilization to the site, advancing four soil borings, characterizing soil <br /> cuttings, and completing the borings as soil gas sampling probes. The soil gas sampling probes <br /> are intended to be located adjacent to the garage and the warehouse portion of the on-site <br /> business, and at the fenceline between the property and the adjacent residences to the east to <br /> evaluate potential health risk to the occupants resulting from soil vapor intrusion. Proposed soil <br /> gas sampling probe locations are shown on Figure 3. <br /> . 5 <br /> The soil borings will be advanced to approximately four feet bgs using a direct push drilling rig. <br /> A discrete soil sample will be collected at the base of each boring using an acetate sleeve. <br /> Each soil sample will be analyzed for site-specific contaminants of concern. Using similar <br /> sampling methods, an additional soil sample from one boring will be collected for physical <br /> property analyses including porosity, density, and moisture content using API Method RP40; <br /> particle size distribution by ASTM Method D4464M; and total organic carbon using the Walkley- <br /> Black method. The data obtained from these analyses will be useful for vapor intrusion modeling <br /> applications. Upon completion of each boring, a temporary vapor probe assembly will then be <br /> installed. <br /> Each vapor probe will be constructed using 0.25-inch outer diamete <br /> with an ESP brand stainless steel wire screen tip implant at the base No <br /> aboveground Teflon vapor probe tubing will be fitted with a swaglok v <br /> vapor sample collection. The annulus will be backfilled with six inch <br /> and overlain with hydrated granular bentonite to seal the annular : ` <br /> interval to prevent ambient air intrusion within the boring annulus, <br /> probe assembly will be secured directly below the ground surface ai <br /> ATC will return to the site to collect vapor samples no sooner than 48 <br /> Sampling Methodology <br /> In an effort to appropriately conduct soil vapor sampling on site, ATC will follow the guidelines <br /> established by the Los Angeles Regional Water Quality Control Board (LARWQCB) and the <br /> Department of Toxic Substances Control (DTSC) in documents entitled Advisory— Active Soil <br /> Gas Investigations dated January 28, 2003 and Interim Final— Guidance For the Evaluation and <br /> Mitigation of Subsurface Vapor Intrusion to Indoor Air dated December 15, 2004, revised <br /> February 7, 2005. <br /> Soi1GasWorkP1an.doc 3 ATC Associates Inc. <br />