An unusual marine outfall off central California, USA

Abstract

This paper concerns Monterey Bay, California, where two prohibited wastewater discharge areas were established in 1971 following sewage pollution incidents. Several south Bay municipalities were forced to close their own treatment plants and outfalls, with the sewage being piped to a central coastal location for combined discharge. Eleventh-hour limitations on coastal access resulted in the outfall's having an unusual Z configuration, with the middle leg perpendicular to some directions of storm wave approach. Construction of the outfall was halted by the El Niño storms of 1982–1983 that destroyed half the trestle and removed countless tons of armour rock. After more difficulties, the pipe was completed in 1984, but then suffered damage from a strong earthquake in late 1989. A year later the outfall was repaired in an extraordinary inside-the-pipe operation. In 1995 and 1996, duckbill valves were placed, in 30 m of water, over all operating diffuser ports. This was done because of impending wastewater reclamation for crop irrigation, and virtual outfall shutdown at certain times. The latest concern has involved the adequacy of diffuser rock protection.