Measure Description

The Watershed Contaminant Reduction Index measures drainage system releases to the North Saskatchewan River from the city of Edmonton, adjusted for population. The index is calculated annually using measured and estimated amounts of sediments, nutrients (ammonia and phosphorus) and bacteria discharged to the river, referenced to a baseline. Sources of these parameters from the City of Edmonton include the Gold Bar Wastewater Treatment Plant, combined sewer overflow sites and stormwater outfalls. An increase in the index is good and means less contaminants were released into the river. A five-year running average is used to smooth out fluctuations due to weather.

Measure Importance

The City of Edmonton is committed to tracking and reducing contaminant discharges into the North Saskatchewan River to reduce the impact these contaminants have on river ecology and downstream communities. Parameters included in the calculation are associated with collection and treatment of wastewater and stormwater and have also been identified as important to the North Saskatchewan River basin by the City’s regulator, Alberta Environment and Parks. The parameters are reported monthly and annually under the City’s approval to operate its sewer systems and are watershed health indicators.

Historical Data

Data sources: Sewer flows and water quality monitored and estimated by the City. Performance data from the Gold Bar wastewater treatment plant forms part of the loading information. Municipal Census and the City of Edmonton Chief Economist estimates (population information). Results from 2010 - 2012 are reported here but the calculation methodology was not comparable to current methodology.

Explanation of Performance

2017 was an average precipitation year, meaning average loads from the stormwater system, and the 2017 index result was 7.2. Continued treatment optimization at Gold Bar Wastewater Treatment Plant has resulted in a decrease of loads discharged into the North Saskatchewan River. Generally, there were fewer contaminants released into the North Saskatchewan River in 2017 than originally forecasted. The city’s current population is also higher than the estimates which were developed in 2014, driving results upward.

Continued improvement of combined sewer system performance along with continued efforts at EPCOR’s Gold Bar Wastewater Treatment Plant on managing and treating wet weather flows was essential to environmental performance. Source control, enforcement of the Drainage Bylaw, development of the Low Impact Development Design Guide, the update of the design and construction standards and citizen education all played a role in improving the index. Overall citizen education about the impact people have on the North Saskatchewan River has always helped to reduce the impact of the City of Edmonton and EPCOR.

Useful Links

For information about the City's strategic plan, The Way Ahead: