Final Environmental Impact Statement. Outfall Replacement for Wastewater Treatment Plant at Fort Kamehameha, Navy Public Works Center, Pearl Harbor, Hawaii

摘要

This environmental impact statement (EIS) evaluates replacement of the existing outfall from the Wastewater Treatment Plant (WWTP) at Fort Kamehameha. The proposed action is to construct a new effluent outfall into the Open Coastal Waters offshore of Fort Kamehameha. Presently, the effluent outfall for the WWTP at Fort Kamehameha discharges into the Pearl Harbor Estuary. This area is classified as a Water Quality Limited Segment (WQLS) by the State of Hawaii Department of Health. Under this classification, discharge of municipal and industrial wastewater effluents to the estuary is limited. Relocation of the effluent discharge to Open Coastal Waters will eliminate effluent discharge to the WQLS of the Pearl Harbor Estuary and the associated future permit limitations and violations. The proposed action is to construct a 3.9-kilometer (2.4-mile)-long, 107-centimeter (42-inch)-diameter outfall, terminating in a 200-meter (656-foot)-long diffuser at a depth of 46 meters (150 feet). The preliminary alternatives to the proposed action, which are considered in this EIS, include underground injection, no action, treatment plant upgrade, infiltration and evaporation, and effluent reuse. A preliminary screening identified underground injection as the only feasible alternative to the proposed action. Based on a detailed analysis of the environmental impacts of the proposed action and the underground injection and no-action alternatives, the proposed action with mitigation as stipulated was found to be the environmentally preferred alternative. There are no identified unmitigable, significant environmental impacts expected as a result of implementing the proposed action. The proposed action is consistent with applicable state and federal water quality and air quality standards.