Transport of Sewage from Victoria's outfalls
It has been argued that: Contrary to what we’ve been told, the currents near the outfalls do not carry the sewage out into the Pacific. Rather, because currents change direction with the ebb and flow of the tide, a lot of the sewage either stays nearby or flows back into Georgia Strait and Puget Sound.
This is the Counter-Argument:
The Victoria outfall discharges pose no threat to Puget Sound, Georgia Strait, Juan de Fuca Strait, or the Pacific Ocean.
Ocean currents in eastern Juan de Fuca Strait consist of tidal, storm driven (See: Flux into the Strait of Georgia) and estuarine components. Superimposed on the tidal and storm driven current components are the more persistent estuarine currents driven by the hydraulic head of the Fraser River as it enters the Strait of Georgia near Vancouver resulting in a net flow toward the Pacific Ocean. In addition, the quantities of dissolved effluent are so small (theoretically 9ppm) that they cannot be measured more than a few hundred meters from the outfalls.
Analysis: Flood tide currents cannot transport anything from Victoria's two deep sea outfalls more than a few kilometers into Haro Strait. The Strait of Georgia is located about 50 kilometers North East of Victoria. Ebb tides flow in the opposite direction out towards Race Rocks. The net effect of the tidal movement component within the daily (25 hour) tidal cycle is close to zero. The estuarine (or residual) current is estimated to consistently flow at rates of 10 to 20 cm/sec occasionally reaching maximums of 40 cm/sec out past Victoria towards the Pacific Ocean.
Conclusions: There is no credible evidence that any significant quantities of sewage from Victoria’s long outfalls enter the Strait of Georgia, Puget Sound or the Pacific Ocean by natural oceanographic processes.
The great volume of fresh water from all the rivers flowing into the Georgia/Puget basin is what drives this residual current. The possibility of minute quantities of dissolved effluent from Victoria entering the Strait of Georgia or Puget Sound through tidal mixing and refluxing processes is as unlikely as effluent discharged from the Annacis Island treatment plant near the mouth of the Fraser River migrating upstream to beyond Chilliwack. This same residual current is also responsible for moving dissolved effluent from Puget Sound into the southern Strait of Georgia and then out through Haro and Juan de Fuca Straits, past Victoria. A model study prepared for the BC/Washington Marine Science Panel in 1994 by Seattle Oceanographer E.D. Cokelet indicated that dissolved effluent in the waters off Victoria originated primarily from Vancouver (100 ppm or 52.1%), Seattle (83 ppm or 43.2%) with less than 5% originating from Victoria (9 ppm). If sewage ever proves to be a problem in our waters (it hasn’t to date), then maybe we should look seriously at where most of it is coming from.