Incentive for Installing Backwater Valves

In 2005, the City of Saskatoon enacted a temporary Flood Protection Program to help protect against sewer backup flooding by providing financial assistance towards the installation of protective plumbing features such as sump pumps and backwater protection valves. This program was later expanded after flooding struck the city again in 2007 and later in 2010.

Understanding and Assessing Impacts

Wastewater backup flooding usually occurs when the domestic sewer system overflows as a result of inflow and infiltration forcing stormwater from severe rainstorms back up through the private-side laterals that connect a household’s plumbing system to the municipal domestic sewer system. Specifically in Saskatoon, weeping tile systems for a large number of homes are connected to basement floor drains. This was identified as the primary cause of rainwater entering the wastewater sewer system during storm events. One simple solution to this problem is a backflow protection valve, essentially a one-way gate installed in the sewer lateral that allows sewage to flow out from the house into the wastewater sewer system but not the reverse. Many older homes do not have such a safeguard in place, leaving them vulnerable to sewer backup. While relatively cheap to install in new development, renovating existing homes to include a sewer backup valve is costly and frequently difficult to retrofit for the average homeowner. Additionally, since weeping tile systems were the primary cause of the basement flooding homeowners were also required to disconnect their home’s weeping tile from the floor drain by installing a sump to expel this water outside the house. The City of Saskatoon opted for a an incentive-based system to encourage this type of renovation by covering most of the costs. It was created as a response to the damaging floods in 2005, 2007, and 2010. These events created the impetus for the program and also helped to inform the planning and execution of it. The first step the city undertook was to create a map of all of the homes affected by sewer backup flooding in the wake of rainstorm. This map allowed them to precisely target the most at-risk areas. This precision targeting was an essential component of the success of the Flood Protection Program. Historically, many municipalities have found it difficult to get high levels of uptake on flood protection renovations, even with financial incentives. The City of Saskatoon, by focusing specifically on high-risk areas, was able to target those homeowners who stood to be the most heavily impacted and, therefore, had the highest incentive to participate.

Identifying Actions

The map of effected homes was supplemented by additional hydraulic modelling to help increase the precision of the targeted incentives. One of the more difficult issues with the implementation of this plan was identifying those homes that had previously suffered damages due to wastewater sewer backup flooding. In many cases, homeowners did not choose to inform the city that their home had experienced a backup event. Furthermore, privacy laws prevented the city from compelling plumbers, insurers, and other private corporations to share information on affected properties. Given the aforementioned value of having accurate mapping to target high-risk areas, this was a major complication that likely hindered the total effectiveness of the program. Ultimately, the city decided to limit protection measures to just those homes in the affected areas, as they offered the highest benefits for the costs, an essential step when operating on a limited budget. A component of the plan that has been cited as critical to its success was the decision to include the local plumbing contractors in the conversation early on, asking them about capacity, interest, and willingness to install protection measures. The city recognized that this program was only the first step in a wider-scoped Flood Protection Program, which is still undergoing further iterations and implementation today.

Implementation

Recognizing that action by homeowners was an essential component of the plan, the City quickly made a variety of tools available to help inform homeowners of the threat they faced and the choices they had available to confront the issue. The City of Saskatoon website hosted articles such as Protective Plumbing: what is it? that helped the homeowner understand their options and how renovating their homes sewer connections would help reduce the chances of backup flooding. The city also originally contracted the management of the program out to a consultant but, not satisfied with the results, reverted back to handling the matter in-house. This created substantially higher strain on the city’s resource, but was deemed to be worth the effort in light of the success of the program. Beginning as a quick response to flooding in 2005, the program has since undergone multiple iterations and has informed subsequent programs of a similar nature such as a Stormwater Business Utility Plan, a Surface Flood Control Strategy, and a new Temporary Flood Protection Plan created in 2017.

Outcomes and Monitoring Progress

This program saw notably higher uptake than similar plans across the country, with around 50% of all targeted homes implementing the sewer protection improvements. The success of the program has been monitored by comparing the incidence rate of sewer backup flooding events in the affected areas and measuring whether or not those homes that undertook protective measured were flooded in subsequent storms; it was determined in subsequent flooding events that roughly 85% of those previously high-risk homes did not suffer another sewer backup flooding incident. Recognizing that the incentives may not have been as strong as necessary, the maximum credit was increased from $2500 to $3000 in 2010.

Next Steps

The backflow prevention program was made available to residents for a six month period following the severe storms of 2005, 2007, and 2010. Although the program has concluded it is possible that further severe storm events that cause wastewater sewer backups may see the program reinstated. Saskatoon’s response to wastewater backups has since changed and has been focused on a new innovation to improve the resiliency of its wastewater system to the high flows generated by weeping tile systems during severe storms. Large tanks (referred to as “superpipes”) have been installed in flood prone areas to act as overflow storage for the wastewater system. Now the overwhelming volume of water generated by weeping tile connections during rainstorms can be safely contained in storage placed below the level of nearby basements, thereby protecting homes until the storm passes and the tanks are drained.

Resources

Link to Full Case Study

Additional Resources