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Jerry Life <br /> March 3, 2014 <br /> Page 11 of 13 <br /> C18) and aromatic fraction (Cs-Cis) within the carbon ranges corresponding to <br /> the available analytical data (C4-C24 for groundwater and C10-C36 for soil). <br /> The toxicity and associated hazards of the TPHs actually present may have <br /> been underestimated or overestimated, depending on the actual composition <br /> of TPHs in soil and groundwater. <br /> Potential hazards from soil exposures are dominated by the aromatic fraction, <br /> whereas potential hazards from groundwater to indoor air exposures are <br /> dominated by the aliphatic fraction. If TPH composition in groundwater from <br /> the C4— C24 range consists of less than 50% C9-Ci8 aliphatics, then potential <br /> groundwater to indoor air hazard is lower. If TPH composition in soil is less <br /> than 50% aromatic and predominantly in the C19_32 aliphatic range, then <br /> potential hazard is lower for direct contact with soil. <br /> Groundwater and/or soil gas sampling for carbon fractions with speciation of <br /> aliphatic and aromatics may provide additional data to reduce uncertainty of <br /> the indoor air risk from TPHs. <br /> 4. RECOMMENDATIONS <br /> Considerable uncertainty exists in HERO's screening-level risk estimates presented <br /> above due to data limitations. The data limitations that most notably affect predicted <br /> risks and hazards are the age of the TPH groundwater and soil data and lack of <br /> speciation of TPHs, followed by data quality issues for the PAH soil data. The Homes <br /> data were insufficient, thus data collected from the ROW were also utilized. HERO <br /> recommends improving the data set by collecting more recent TPH data with speciation. <br /> HERO also recommends implementing some or all of the below actions to reduce <br /> uncertainties, followed by re-assessment of screening-level risks. <br /> • Obtain PAHs soil concentration data for MS/MSD samples from Lancaster Labs <br /> and calculate bounding risks for residential soil exposures. <br /> • Ascertain whether the potential for pipeline workers engaged in long-term soil <br /> invasive activities exist, and if so elucidate the actual exposures by pipeline <br /> workers. <br /> • Conduct sampling and analyses. <br /> o Current groundwater and soil data may demonstrate that TPH <br /> concentrations are significantly reduced. Based on the results of this <br /> sampling and analysis data, the need for additional step out sampling can <br /> be evaluated. <br /> o TPH fractions analyses from soil, groundwater and soil gas with speciation <br /> of aliphatics and aromatics within each carbon range fraction to more <br /> accurately predict risks. <br /> o Accrue PAHs ROW soil data without QA/QC issues. <br /> file:20140303JL.doc <br />