PH18 Assessing Human/Environment Interactions
Exhibit Hall
8:00 AM - Thursday
(PH205) Ecological risk assessment for the COB Energy Facility, Bonanza, Oregon: air emissions and process wastewater application.
Arenal, Christine1, Tsao, Chih1, Sample, Bradley1, Irvine, Cameron1, 1 CH2M HILL, Sacramento, CA, United States
ABSTRACT- A screening-level ecological risk assessment (ERA) was conducted to determine the potential risk to plants, soil invertebrates, and wildlife from air emissions at the California-Oregon Border (COB) Energy Facility (Facility), and, separately, the potential risk of using process wastewater from the Facility to irrigate 31 acres of pasture and to improve grazing forage yield in areas currently without irrigation. The first scenario evaluated the potential risk from air emissions (and deposition to surface water) to aquatic organisms and to bald eagles (exposure through food). Upland areas surrounding the Facility were also evaluated for risks to plants, soil invertebrates, and birds and mammals resulting from terrestrial deposition of air emissions. Under the second scenario, possible risks to terrestrial receptors from recycling process wastewater for irrigation were assessed. Metals deposited from air emissions or contained in the process wastewater were the primary chemicals of potential ecological concern (COPECs). The ERA employed conservative assumptions, maximum estimated media concentrations, and screening toxicity values such that COPECs that passed the screen were considered to pose no significant risk to ecological receptors. COPECs that failed the screen were reevaluated using more realistic assumptions. Several metals failed the terrestrial screening under both scenarios; however, these exceedances were most often driven by background concentrations with negligible contribution from deposition of air emissions and process wastewater application. Boron-sensitive plants would be at risk in the process wastewater application area; therefore, only boron-tolerant species (e.g., alfalfa) were recommended for planting in the irrigation area. Under the air emissions scenario, none of the COPECs exceeded screening benchmarks for aquatic receptors, but mercury exposure to bald eagles exceeded oral toxicity benchmarks. However, the magnitude of exceedance was low and the estimated mercury concentrations in water due to air deposition were highly conservative (i.e., assumed 100 percent deposition). Therefore, no risk to bald eagles from air emissions was predicted. In conclusion, no significant ecological risks related to Facility air emissions or application of recycled process wastewater were identified.
Key words: air emissions, ecological risk assessment, recycled process wastewater, energy facility