The effects of untreated municipal sewage discharge to the marine environment off Victoria, British Columbia, Canada

The Victoria area (British Columbia, Canada) discharges screened wastewater through two long deep outfalls (Macaulay and Clover Point) into an oceanic environment characterized by strong turbulent tidal flows. Monitoring of the receiving waters has indicated that conventional water quality parameters have not been affected by the discharges. Fecal coliform levels above the outfalls are periodically elevated but remain well below the swimming standard. Shoreline studies of fecal coliform levels have shown that the deep outfalls have not measurably affected water quality at beaches. Recently, monitoring efforts have concentrated on effects to the seafloor environment. At Macaulay Point, sediment chemical levels of concern were confined to within 100 to 400 m of the outfall. Similarly, sediment toxicity was detected at stations up to 400 m from the diffusers. This toxicity was limited to effects on growth and development. Survival was not affected. The benthic infaunal community exhibited a typical response to organic enrichment. Within 100 m of the outfall abundance was increased and richness depressed. At Clover Point sediment chemical levels of concern were confined to within 100 to 200 m of the outfall. Tissue chemistry of resident mussels showed no consistent pattern with distance from the outfall. Some tissue chemicals increased with distance from the diffuser while others decreased. Overall the impact of the outfalls on the seafloor was found to be minimal and restricted in extent. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.