WRRCTR No. 76 A Study of the Effects of Secondary Effluent on Waimano and Waiawa Streams

Abstract

A field study was made between September 1972 to May 1973 to assess the water quality changes in Waiawa and Waimano Streams, particularly the effect of chlorinated effluent from the Pacific Palisades Sewage Treatment Plant on the receiving stream waters. Some changes were very apparent, especially those of an aesthetic nature, the visible change in the color and turbidity of the water and the sulfurous odor of septic sewage. These obvious changes were indications of changes in water quality which could only be determined in the laboratory by chemical analysis. The actual degree of change in stream quality and amount of recovery cannot be determined until Palisades treatment plant ceases operation, and sewage effluent is no longer discharged into the stream. Waiawa Stream is an intermittent stream with a large drainage area. The developed areas within the Waiawa basin represent 20-25 percent of the total drainage area, but the sewage flow from one such developed area, Pacific Palisades, is the source of perennial flow for the lower section of Waiawa Stream. However, even with the large drainage area and intermittent streamflow, self-purification takes place in the short distance from the point of sewage effluent discharge to Pearl Harbor.