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4.0 Preliminary Comments Regarding Remedial Approaches <br /> Remediation of submerged sorbed, dissolved and SPH at this property are constituent by the <br /> following factors Z <br /> 1 <br /> • Tight Access This includes building cover/infill, vehicle parking by a tenant business, <br /> abundance of government or utility-owned, utility poles, light standards and wires, <br /> and proximal city and/or stated-owned "busy" roadways <br /> • Depth Hydrocarbon contamination is below 24 feet and may only be cost-effectively <br />' accessed by drilling and manipulation of groundwater flow or chemistry (such as <br /> ozonation or use of other in-situ oxidants or biostimulants) <br /> • Formation Heterogeneity and Contrasting Permeability Hydrocarbons shallower <br /> than 40 feet are present to silty sediment which will resist thorough remediation by <br /> pumping or most methods of chemical infection Hydrocarbons between 40 and about <br /> 60 feet are present within gravelly sands, sands and silty sands are probably amenable <br /> to remediation by pumping and/or injection <br />' • SPH Separate-phase hydrocarbon was observed in sands within the only boring that <br /> was cored SPH is toxic to bacteria and hence resistant to biodegradation, and <br /> challenging to remediation by most in-situ chemical methods The extent of SPH is <br /> also unknown <br /> • Desorbtion Kinetics Hydrocarbon present within the saturated zone down to 40 feet <br /> probably occurs mainly as sorbed material It will desorb slowly and only in <br /> proportion to the relative removal and absence of dissolved hydrocarbon in the <br /> directly-adjoining pore water The kinetics of desorbtion are commonly the <br /> ' rate-limiting factor in the remediation of hydrocarbons within silt aquifer systems <br /> ' SacOP N MwhPubifM f Don Aadg-r RpfSMRVS-ng 2006 SIR(August)dao 4_i <br /> 82308 <br />