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�ihase El Environmental Site Assessment <br /> Heritage Square <br /> Page 10 <br /> Condor believes that natural "attenuation would be an appropriate remediation option due to the non- <br /> presence of constituents of concern on the site. Natural attenuation is a process of site characterization, <br /> risk assessment, and monitoring of the remediation processes. Due to the length of time the contaminants <br /> have potentially been present on site (approximately 50 years), the character of the contaminants, and the <br /> subsurface conditions, this site would benefit most from the biodegradation that is a main component of <br /> natural attenuation. The length of time of potential contaminant presence on site is estimated from a <br /> reasonable approximation of the date of conversion of the Heritage Square boiler from heavy hydrocarbon <br /> fuel to natural gas. <br /> Analysis of field observations and the laboratory analytical results of the soil samples indicate that further <br /> subsurface soil investigation of the site is not necessary. Condor believes the petroleum contamination is <br /> located in a relatively limited area due to the tight clay soil types at the site. The site will naturally <br /> attenuate itself over time and the contamination appears to be contained on site. <br /> 8.4 RECOMMENDATIONS <br /> Based on the results of the Phase 11 ESA investigation, Condor recommends the following: <br /> • Close TK1 in place in accordance with the regulations established by .EHD and the City of <br /> Stockton Fire Prevention Division (FPD). <br /> • Pursue proper closure of TK2 with off-site tank owner in order to prevent any potential further <br /> impact to the site from this off-site source. <br /> • Destroy the abandoned well located on site in accordance with the regulations established by <br /> EHD. <br /> i+� CONDOR <br />