Site Risk

A baseline human health risk assessment (HHRA) and screening-level ecological risk assessment (SLERA) were conducted as part of the SWMU 58 RFI.

An HHRA was performed to evaluate the potential human health effects associated with past activities at SWMU 58. Using the results of the human exposure assessment and toxicity information, potential human health risks for each Contaminant of Potential Concern (COPC) and selected exposure pathway were evaluated. Results of the HHRA indicate that the cumulative cancer risk associated with both surface soil and total soil for maintenance workers, and total soil for excavation workers, adult residents, and child residents were below or within the U.S. Environmental Protection Agency (USEPA) target risk range of 1E-06 to 1E-04. The non-carcinogenic Hazard Index (HI) was below 1 for maintenance workers, excavation workers, and adult residents. For child residents, the non-carcinogenic HI was equal to 1.1. However, there were no predominant COPCs representing non-carcinogenic hazards (i.e., no chemical HI was equal to or exceeded 1). Trichloroethene (TCE) and benzo(a)pyrene were the risk drivers for the limited potential human health risk calculated.

A SLERA was performed to provide an estimate of current and future ecological risk associated with potential hazardous substance releases at SWMU 58. Environmental Effects Quotients (EEQs) and hazard indices were estimated for five selected receptor species, and direct contact exposure for terrestrial invertebrates was assessed, as these invertebrates may serve as a food supply for some of the selected receptor species. Initial results indicated the potential for advers effects to some of the five species, however, based on likely overestimates of (1) toxicity, and, (2) uptake of inorganics by earthworms from soil; and, that no wildlife rare, threatened, or endangered species have been confirmed at the SWMU 58 study area, no further action is recommended for the site for food chain exposure considerations. A similar recommendation of no further action results from the finding of limited potential for a reduction interrestrial invertebrates that may serve as a food supply for higher order wildlife, based on direct contact considerations.