Ecologic Responses to Ocean Waste Discharge: Results from San Diego's Monitoring Program

As a part of a program of continuing review of the performance of San Diego's wastewater outfall, the San Diego Regional Water Quality Control Board and the State Water Resources Control Board directed Water Resources Engineers, Inc. (WRE) to encode, analyze and interpret monitoring data collected by the city over the period of 1962 to 1969. All available monitoring data through December 1969 were encoded and a series of computerized analytical routines developed by WRE were employed in the analysis. Work was performed by Dr. Carl W. Chen under the overall supervision of Dr. G. T. Orlob, president of WRE. Dr. Robert Cooper of the University of California advised on matters relating to pollution ecology. The current study, following several related investigations by WRE and others, was directed particularly to evaluation of ecological, physical, and chemical changes in the ocean environment which may have resulted from waste discharges since the outfall was first placed in operation in August, 1963. Comparisons were made with a "pre-discharge" period, 1962-1963, and trends in water quality, sediment characteristics, and wastewater characteristics were estimated for succeeding periods. Results of the present study confirmed earlier conclusions by WRE and other investigators that changes in water and sediment quality in the vicinity of the outfall off Point Loma have occurred at significant levels and that these are correlatable with changes in the operation of the outfall and the waste load imposed on the ocean environment. The general conclustion, also advanced in a previous study by WRE in 1967 that ecologic changes have been significant but subtle, was also supported by the more exhausted review of ecologic data undertaken in the present study.