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Jerry Lile <br /> March 3, 2014 <br /> Page 9 of 13 <br /> Landscaping or clean fill cover reduces exposures and risks for current <br /> residents. Based on the data presented combined with the landscaping <br /> preventing routine contact with subsurface soil, risks are likely <br /> overestimated for current residents. <br /> b) Construction Workers <br /> Potential cumulative risks for construction workers engaged in soil <br /> invasive activities for 90 days or less are below the risk management point <br /> of departure of 1 x 10"6 for cancer risk, but hazards slightly exceed a HI of <br /> 1 indicating potential for non-carcinogenic effects from TPHs. <br /> Potential cumulative risks for construction workers engaged in soil <br /> invasive activities for 1 year (potentially OVP/Chevron-contracted piveline <br /> workers) are within the risk management range of 1 x 10-4 to 1 x 10" for <br /> carcinogenic risks from inhalation of cobalt, while hazards are somewhat <br /> above the threshold HI of 1 due to TPHs and metals (cobalt and nickel). <br /> o TPH - Current upper bound average concentrations are unlikely to be <br /> higher and most likely less than the maximum from the 1998 TPH data <br /> due to probable natural attenuation over the past 15 years. <br /> o Metals- Risks and hazards are in excess of the risk management point <br /> of departure for construction workers engaged in soil invasive activities <br /> for 1 year due to inhalation of cobalt and nickel in soil. <br /> o While an exposure duration of 1 year is not expected for the small area <br /> of Surland Homes, pipeline workers may be engaged in soil invasive <br /> activities with exposures well beyond 1 year. If pipeline workers are <br /> employed and routinely involved in soil invasive activities along the <br /> pipeline (then use of an exposure duration of 25 years (rather than 1 yr <br /> or 90 days) is appropriate and results in higher risks. <br /> o HERO recommends risk managers ascertain whether the potential for <br /> pipeline workers engaged in long-term soil invasive activities exist, <br /> then consider and/or elucidate the actual exposures by pipeline <br /> workers to factor into their risk management decision; alternatively, <br /> HERO can further refine the risk estimates using the actual exposures <br /> by the pipeline workers prior to risk management decisions. <br /> TPH Uncertainties: Significant uncertainty exists in HERO's hazard <br /> estimates due to assumptions necessitated by lack of speciation of TPH <br /> soil concentrations into aliphatic and aromatic carbon range fractions. <br /> See discussion below on TPH-related uncertainties. <br /> file:20140303JL.doc <br />