SITE INFORMATION AND CORRESPONDENCE

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Ms.Lori Duncan November 15,2011 RE: 2911 E.Fremont St,Stockton,CA Page 13 of 14 Analytical results of ambient and indoor air samples collected at the site indicate that residual contamination beneath the warehouse building is likely contributing to low-level petroleum constituents detected in indoor air. However,both indoor air and ambient air samples collected at the site contained TPHg,benzene,toluene,ethylbenzene,and xylenes in air. Notably,benzene in all samples was present at levels exceeding the conservative screening level (CHHSL) established by Cal/EPA-OEHHA. Since ambient and indoor air results for several chemicals exceeded industrial/commercial CHHSLs and/or ESLs,L&P conducted a site specific Tier 2 risk evaluation by calculating site specific cancer risk and hazard quotients using equations and parameters outlined by Cai/EPA-DTSC. The hazard quotients for all samples collected at the site were below 1.0 and,therefore, considered insignificant health risk(non-carcinogenic). The calculated risk of up to 1.75 E-06 for ambient air and 4.58E-06 for indoor air are within the lower end of the acceptable range of 1.0E-04 to 1.0E-06 established by the US EPA. Based upon investigations and remedial activities conducted at the site, L&P recommends the following: 1. Present the results of subsurface investigation activities,remediation activities,and human health risk evaluation to site workers and answer any questions that may arise; 2. Consider the site for closure as a low risk contamination case, based upon the removal of all accessible contamination soil, the absence of a direct exposure pathway, the apparent minimal migration pathway of contaminants to shallow groundwater,and the calculated cumulative cancer risk is at the low end of the acceptable range established by US EPA for commercial/industrial properties. The potential for direct exposure at the site is limited in its current configuration because the entire site is capped with concrete or asphalt. Z However,since petroleum hydrocarbon vapor persists in the vadose zone,any future development at the site should consider engineered controls to mitigate vapor intrusion concerns,such as a passive vent system, as appropriate. REFERENCES California Environmental Protection Agency,Department of Toxic Substances Control(DTSC),October 2011, Final Guidance for the Evaluation and Mitigation of Subsurface Vapor Intrusion to Indoor Air (Vapor Intrusion Guidance). California Environmental Protection Agency, Office of Environmental Health Hazard Assessment (OEHHA),January 2005,Use of California Human Health Screening Levels(CHHSLs)in Evaluation of Contaminated Properties. California Environmental Protection Agency, Office of Environmental Health Hazard Assessment (OEHHA), September 2010, California Human Health Screening Levels for Ethylbenzene. 10759-EXC SUMMARY LTR