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0 0 <br /> PCE was detected in all four soil gas sample and one duplicate sample. Soil gas concentrations <br /> were converted into theoretical indoor air concentrations using the Department of Toxic <br /> Substances Control (DTSC) recommended attenuation factor. Applying the applicable DTSC <br /> foundation attenuation factor of 0.05 resulted in a calculated theoretical indoor air concentration <br /> of 165 micrograms per cubic meter (gg/m) of PCE and 17.5 gg/m3 of TCE. The conversion <br /> resulted in indoor air concentrations above the DTSC recommended value for PCE of 2.08 µg/m3 <br /> at four locations and above the EPA Regional Screening Level (RSL) for TCE of 3.0 µg/m3in <br /> one location(SG3). <br /> Due to the presence of PCE and TCE in sub slab soil gas samples, Partner recommended soil and <br /> groundwater sampling to delineate the PCE and TCE impacted media at the subject property. <br /> The subsurface is expected to consist of sands and gravel with depth to bedrock unknown. Due <br /> to the expected lithology to be encountered at the site, the drilling method has defaulted to direct- <br /> push technology. <br /> Based on available information from the State Water Resources Control Board (SWRCB) <br /> GeoTracker Website (Global Identification Number T06077000), a leaking underground storage <br /> tank site is located approximately 400 feet north of the subject property. The water table at this <br /> location was at a depth of approximately 9 to 13 feet below ground surface (bgs) during 2005 <br /> with a flow direction to the south-southwest. Given the recent and ongoing drought it is likely <br /> that the water table is at least several feet deeper than it was in 2005. <br /> Objective <br /> At the request of the client, Partner will conduct Additional Phase II Sampling. The <br /> investigation scope will include the advancement of four borings to facilitate the collection and <br /> analysis of soil and/or groundwater samples. The main objective of the project will be to <br /> delineate chlorinated solvents detected in sub-slab soil gas collected as part of the Phase II <br /> Subsurface Investigation. Please note that contamination delineation is an iterative process and <br /> that the investigation design was based on currently available information. Therefore, additional <br /> sampling and/or laboratory analysis beyond the proposed scope of work may be required to fully <br /> characterize the contamination in the vicinity of previous detected CVOC impacts. <br /> Scope <br /> Subsurface Sampling <br /> Sampling procedures will conform to the requirements of the SWRCB and the United States <br /> Environmental Protection Agency (EPA). A state-certified laboratory will analyze the samples <br /> and the project will be performed under the responsible charge of a qualified environmental <br /> professional. Analytical results will be compared to the August 2104 Central Valley Regional <br /> Water Quality Control Board Water Quality Goals and the September 2010 California Human <br /> Health Screening Levels. <br /> Partner will perform the following tasks for the Subsurface Sampling: <br />