Impact on Marine Benthos of Wastewater Discharge

The City of San Diego presently discharges about 110,000,000 gal/day of primary treated wastewater through an ocean outfall located 11,500 ft offshore of Point Loma in 220 ft of water. The response of the marine environment to this discharge has been monitored continuously since 1962, about 15 months before operation of the treatment plant commenced. Analysis of data on sediment quality and benthic animal populations collected from stations surrounding the outfall diffuser indicates that the marine environment has been stimulated biologically. Biomass and the numbers of organisms in the benthos have generally increased. Changes in these indicators of environmental impact are noted to follow the historical pattern of suspended solids loading. Overall, the marine environment off Point Loma is observed to accept the waste load imposed by the discharge without adverse effects.