Imagine using an unassuming corner of your street, yard, or local park to improve the quality and security of water and the Great Lakes. It’s possible with green infrastructure and low impact development (LID). These approaches can create beautiful garden or landscape features that also remove some of the most problematic urban nonpoint pollutants affecting our environment.
Traditional approaches to stormwater management, such as stormwater management ponds, prioritize peak flow and flood control. They have the unintended consequences of warming stormwater to unhealthy levels and reducing dissolved oxygen required by fish and other organisms. The result is the deteriorated quality and functionality of our most heavily impacted urban streams.
As our collective knowledge evolves, so do our stormwater management approaches and regulations. The Ontario Ministry of Environment and Climate Change is currently updating their stormwater management guidelines, which will place greater emphasis on LID and reducing runoff volumes.
Evaluating options based on experience
We have been working closely with our municipal partners and other stakeholders to construct and monitor LID practices for the last six years. Our monitoring program focuses on the long-term performance of different types of LID practices. We have evaluated the results of LID practices installed under a variety of unique and challenging conditions, looking specifically at water quantity and quality results.
Our performance monitoring data shows that LID can reduce annual runoff volumes by up to 80 per cent and remove 80 per cent of suspended solids, which are harmful to aquatic environments. Problem nutrients like phosphorous are reduced by more than 80 per cent, and filtered waters are cooled by more than 5oC, which is vital for cold-water fish. As well, heavy metal loads have been reduced from 50 to 90 per cent.
Some Ontario municipalities—such as Mississauga, Toronto, and Peel Region—have started to use these results to inform new infrastructure design standards along roadways, parks, and within institutional spaces. It’s encouraging to see municipalities at the forefront. Unfortunately, 75 per cent of the GTA was built prior to any sort of flood control and 85 per cent prior to any water quality control. Nearly 60 per cent of this land is privately held.
We must look beyond public lands if we are serious about curbing stormwater pollution and localized flooding. The realities of climate change require us to be flexible.
Since 2008, the GTA has been hit with three 100-year storm events. This trend is likely to continue or get worse. Innovative LID solutions can go a long way towards alleviating these issues. While private lands present some of the greatest opportunities for LID implementation, they also face the greatest barriers.
Research to action
Research shows that the largest barriers to LID implementation are the upfront costs and the extended payback period, even in situations involving stormwater charge and credit programs. How can we expect to see further reductions in urban stormwater pollution and wide-scale LID adoption without offering a viable business model for cash-strapped private landowners?
Using established programming as a model, Credit Valley Conservation is leading a research project to provide collaborative solutions for private landowners that will allow them to share the costs and benefits of LID. To address urban non-point source pollution, we need a distributed approach to filtering, polishing or treating, and reusing stormwater. Strategically placing LID is the best way to achieve this.
Seeking viable business for private landowners
Even when a utility offers financial incentives to improve stormwater management, the adoption of water technologies by private landowners is hindered by the return on investment. In response, many American cities who are leaders in the field have begun moving towards a model that supports aggregation of water management technologies on private property. The benefit? It supports a reduction of costs related to design, construction, operation, and maintenance (O&M) for private properties owners. However, municipalities don’t currently have a process in place to make use of these tools to support implementation.
Credit Valley Conservation has initiated a project that will ultimately support wide-scale adoption of decentralized LID stormwater practices in Ontario on private lands through public-private partnerships.
Phase 1: Gap analysis and development of discussion papers that will explore topics such as market-based economic instruments, municipal and private adoption requirements, and potential aggregation models, 2017.
Phase 2: Development and refinement of an economic model that will harness grants, economies of scale, and utility rebates to share design, construction, and O&M costs on private properties. Development of an implementation framework to foster aggregation of private properties, 2017/2018.
Phase 3: Apply the economic model and implementation framework to a test catchment area, 2018/2019.
Jennifer Dougherty is a manager of water resources and water quality protection, Kyle Vander Linden is a senior specialist of integrated water management, Phil James is a manager, of integrated water management, Deb Martin-Downs is CAO, and Bill Trenouth is a water resources for Credit Valley Conservation Authority.
One key incorrect statement – most localized flooding in Ontario is generally related to wastewater systems (sewer back-up), because flood plain management policies have been effective since Hurricane Hazel. LID retrofits actually harm wastewater systems by infiltrating water, increasing groundwater levels and aggravating extraneous flows in wastewater systems. Most urban flood damages are in partially separated wastewater service areas (based on statistical analysis of 2000, 2005 and 2013 flooding in Toronto and Markham) that are sensitive to infiltration. These issues are explained in my recent post :
On the topic of uncontrolled urban areas and costs, there are over 850,000 hectares of it in Ontario – at an average cost of $390,000 per hectare for LID retrofits (including several CVC projects), the costs are staggering – $332 BILLION. This is 50 times greater than the entire Ontario stormwater infrastructure deficit (Eco Commissioner estimated at a mere $6B last week). Given this it would be worthwhile to look critically beyond often subsidized demonstration projects and look realistically at costs and the feasibility of any wider implementing of LIDs across existing urban areas in Ontario.
Good time for frank discussion on costs and alternative measures for managing pollution too (including more cost effective prevention measures like banning residential fertilizer, etc.)
PS – CVC claims of 25% cost savings have been shown to be inaccurate for road retrofits – in fact there is an almost 40% cost premium. See my blog post at hte link above for details.
Robert J. Muir, M.A.Sc., P.Eng.