Sanitary & Combined Overflow Locations (DP033-3)
Discussion Paper Summary
To date, there are three main wastewater treatment strategies being considered:
- Option 1 - Regional Resource Recovery
- Option 2 - Regional/Local Resource Recovery
- Option 3 - Local Resource Recovery
This paper describes the locations and magnitudes of overflows that are not handled by the primary treatment facilities under the various strategies.
One of the most important concepts to note when looking at sanitary sewer overflows is the "return period." This simply means the return period of a storm specifies the probability of how often a given storm event will occur. A 100-year return period storm should, on average, occur once every 100 years. The CRD is using a 100-year return period to help gauge how to plan and build wastewater facilities, in order to prevent overflows.
Since inception of the CRD Liquid Waste Management Plan, facility upgrade plans have been in place to work towards the ultimate elimination of overflows below minimum acceptable return periods. As previously discussed, this is a 100-year return period in most of the CRD system. Examples of facility upgrades that have already been completed to achieve this goal include the Marigold storage tank and the Trent St. wet weather pump station. Others, like the Craigflower pump station, are not yet completed. All of these upgrades were originally based on the assumption that wastewater conveyance would continue to occur to just Macaulay and Clover Points.
When new treatment facilities come into being, many of the bottlenecks in the system will be bypassed or see reductions in flow. This will mean significant reductions in overflow frequency and volumes. The required facility upgrades that remain after the treatment facilities are in place will also likely be smaller in scope and cost than originally planned as a result.
For details on the potential flows for each wastewater treatment strategy, please see the full discussion paper, available in the Document Archive.
© Image courtesy of Evan Leeson