Dispersion calculations for non-radiological hazardous chemical emissions from the Defense Waste Processing Facility and related activities

Abstract

The Environmental Protection Agency's (EPA) Industrial Source Complex -- Short Term (ISCST) air dispersion model was used to examine potential atmospheric impacts of routine benzene and mercury emissions from the Defense Waste Processing Facility (DWPF), In-Tank Precipitation (ITP) facilities, and the Saltstone Facility. The highest model estimated 8-hour average ground-level benzene concentrations were found to occur in the immediate vicinity of the ITP filter/stripper building (241-96H). Subsequent model calculations were used to determine minimum stack release heights that would be necessary to achieve compliance with this workplace exposure standard for currently anticipated emission levels. The highest 24-hour average site boundary concentrations of benzene and mercury generally occurred to the north of S and H areas. Concentrations were well below the ambient concentration standards that have been identified for these substances in an air toxics policy proposed by the State of South Carolina. Estimates of annual average benzene concentrations for offsite locations were used to estimate the excess lifetime cancer risk. Assuming continuous 70-year exposure to the estimated annual benzene concentrations, the excess cancer risk to the maximum exposed individual was estimated to be 3 {times} 10{sup {minus}7}. Similar lifetime exposure summed over the surrounding population resulted in an estimated average of 6 {times} 10{sup {minus}4} excess cancers per year. 14 refs., 1 fig., 7 tabs.