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Ms.Lori Duncan
<br /> February 28,2012
<br /> RE:2911 E.Fremont St,Stockton,CA
<br /> Page 5 of 6
<br /> the floor of the warehouse is contributing significantly to indoor air,since ambient air samples also contained
<br /> gasoline constituents. Low levels of PCE were detected in soil, groundwater, and soil vapor samples
<br /> collected at the site,but not in the indoor air or ambient air samples,which further suggests that subsurface
<br /> contamination remaining beneath the floor of Warehouse#2 is not the sole source of low level detections in
<br /> indoor air. Based upon the data collected at the site,it appears likely that the primary contributing source of
<br /> detectable chemicals in indoor and ambient air at the site are from ongoing site activities and ambient sources,
<br /> such as automobile traffic on the surface streets near the site.
<br /> Although ambient and indoor air contained TPHg and benzene at levels marginally exceeding their respective
<br /> screening levels,L&P has concluded that the calculated risk of up to 1.75 E-06 for ambient air and 4.58E-06
<br /> for indoor air are within the lower end of the acceptable range of 1.0E-04 to 1.0E-06 established by the US
<br /> EPA,as presented in previous submittal prepared be L&P(November 15,2011 and January 11,2012).
<br /> Based upon investigations and remedial activities conducted at the site,L&P recommends that EHD close the
<br /> site as a low risk contamination case,based upon the removal of all accessible contamination soil,the absence
<br /> of a direct exposure pathway, the apparent minimal migration pathway of contaminants to shallow
<br /> groundwater,and the calculated cumulative cancer risk is at the low end of the acceptable range established
<br /> by US EPA for commercial/industrial properties.The potential for direct exposure at the site is limited in its
<br /> current configuration because the entire site is capped with concrete or asphalt.
<br /> REFERENCES
<br /> Air Toxics LTD., Guide to Air Sampling&Analysis
<br /> California Environmental Protection Agency, Department of Toxic Substances Control (DTSC),
<br /> October 2011, Final Guidance for the Evaluation and Mitigation of Subsurface Vapor Intrusion to
<br /> Indoor Air(Vapor Intrusion Guidance).
<br /> California Environmental Protection Agency, Office of Environmental Health Hazard Assessment
<br /> (OEHHA), January 2005,Use of California Human Health Screening Levels (CHHSLs) in Evaluation
<br /> of Contaminated Properties.
<br /> California Environmental Protection Agency, Office of Environmental Health Hazard Assessment
<br /> (OEHHA), September 2010, California Human Health Screening Levels for Ethylbenzene.
<br /> Krazan & Associates, Inc., June 10, 2010, Phase II Limited Subsurface Investigation, United Rentals,
<br /> 2911 E. Fremont Street, Stockton, California 95205.
<br /> Lee & Pierce, Inc., January 19,2011, Limited Subsurface Investigation Report, Fremont Gate LLC,
<br /> 2911 East Fremont Street, Stockton, CA, L&P #10759
<br /> Lee & Pierce, Inc.,November 15, 2011, Source Removal Excavation and Indoor Air Sampling
<br /> Summary Report, Fremont Gate LLC, 2911 East Fremont Street, Stockton, CA
<br /> 10759-Vapor Sampling
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