Stormwater: Our Neglected Headwaters
Rain or snow melt – that does not infiltrate the soil, get absorbed by plants or evaporate – flows across the land and into the nearest river or lake. This is called stormwater runoff. As stormwater moves through a watershed, it causes water levels and rates of stream flow to increase, which can cause flooding, erosion, decreased water quality, and alterations to stream channels and aquatic habitat.
In urban areas, where pavements, roofs and other impermeable surfaces replace much of the natural ground cover, this process is intensified mainly because less water can infiltrate the ground. The hydrologic characteristics also differ between natural and urban areas (Figure 4.5.1). Urban rivers can have too little flow in dry weather and too much flow during storm events. The natural cover in rural areas slows runoff and retains water, releasing it slowly and moderating the highs and lows of stream flow. In addition, the stormwater in urban areas can contain high levels of suspended solids, nutrients, bacteria, heavy metals, oil and grease, pesticides, sodium and chloride from road salt, lawn fertilizers and residues from tires. Urban stormwater is a major source of pollution in the Great Lakes and Lake Simcoe.
Figure 4.5.1. Natural landscapes like forests, wetlands and grasslands allow rainwater and snowmelt to infiltrate into the ground, reducing
the amount of runoff. In urban areas where there are more impervious surfaces like roads, parking lots and rooftops, less rainwater and
snowmelt filters into the ground and runoff is increased. Source: U.S. Environmenal Protection Agency.
Stormwater Management
Generally speaking, one of the primary objectives of stormwater management is to slow the movement of water in order to reduce its negative impacts on watercourses, shorelines, built structures, aquatic life and habitat. The goal is to mitigate the effects of urban development on the natural hydrological cycle. Historically, stormwater management practices primarily focused on controlling peak flows to reduce flooding and erosion (for example through piped drainage systems and combined sewers). However in the 1980s, the practice shifted in response to fish habitat concerns to address water quality issues (for example, through the use of ponds and other endof- pipe controls to treat stormwater). Prudent management now incorporates a sequential series of stormwater controls or facilities (i.e., lot-level, conveyance, and end-of-pipe) to maintain natural water volumes and flow rates (Table 4.5.1). The series of controls or facilities is called a stormwater management system or treatment train. Rather than relying solely on end-of-pipe controls, like stormwater ponds, a treatment train approach stresses pollution prevention and can incorporate low-impact development practices at the site level.
| Table 4.5.1 Controls and Facilities in a Stormwater Treatment Train | ||
|---|---|---|
| Lot-level Options | Conveyance Options | End-of-Pipe Options |
| Rooftop storage (green roof) | Reduced lot grading | Wet Ponds |
| Parking lot storage | Infiltration trenches | Constructed Wetlands |
| Subsurface storage | Pervious pipe systems | Dry ponds |
| Rear yard storage | Grassed swales | Filters |
| Rainwater harvesting | Vegetated filter strips | Infiltration basins |
| Permeable pavement | Oil/grit separators | |
The management of stormwater is the responsibility of municipalities and property owners (including developers) in Ontario. The governance for stormwater management falls under the jurisdiction of several different government bodies such as Fisheries and Oceans Canada, the Ministry of the Environment (MOE), the Ministry of Natural Resources (MNR), the Ministry of Municipal Affairs and Housing (MMAH), municipalities, and conservation authorities. For example, municipalities usually require developers to incorporate stormwater management facilities in their subdivision plans in order to obtain Planning Act approvals. In most cases, the developer also must obtain a Certificate of Approval (C of A) under the Ontario Water Resources Act, authorization under the federal Fisheries Act, a permit under the Conservation Authorities Act and, occasionally, a permit under the Endangered Species Act, 2007.
Maintain and Monitor
A key function of stormwater facilities is to trap sediment and toxic contaminants before they reach rivers and lakes. It is vital that accumulated sediments be removed periodically to ensure that facilities function properly and to maintain the original pond depth – otherwise the contaminants will simply be washed downstream. It is also important to regularly clean out oil/grit separators (underground structures used to remove sediment) for them to function properly (Figure 4.5.2). If accumulated sediment is not removed, stormwater ponds have an estimated operational lifespan of 5 to 15 years; many ponds across Ontario have exceeded their life expectancy or will begin to reach expected sediment capacity within the next few years.
Figure 4.5.2. Stormwater can contain many contaminants, such as tire debris, petroleum, cooking grease, dust and metals. These jars
contain stormwater products collected by an oil/grit separator located in a commercial area north of Toronto. If oil/grit separators are not
cleaned out, these products would enter lakes and rivers.
During construction, the maintenance of the stormwater facility (e.g., ponds and oil/grit separators) is the responsibility of the developer. Once constructed, it becomes the responsibility of the property owner. In most cases, the facility becomes part of municipal infrastructure, and the municipality assumes the duty to operate, maintain and monitor.
MOE’s Stormwater Management Planning and Design Manual (2003) provides some guidance on the inspection, monitoring and maintenance of stormwater management facilities. For example, it recommends that owners or managers prepare an annual maintenance report and use inspections to determine required maintenance activities. MOE can also incorporate monitoring, inspection and maintenance as conditions in Cs of A. However, MOE has not developed monitoring standards for stormwater management facility approvals – conditions are determined on a site-by-site basis.
Some municipalities have established regular stormwater monitoring programs to ensure that facilities are functioning properly and to inform their maintenance schedule. The Town of Richmond Hill’s program, for example, has been in place for over 10 years. Through its monitoring program, the town discovered that there were nearly 30 projects that needed major work, including the rehabilitation of the Pioneer Park Stormwater Management Facility. In summer 2010, Richmond Hill completed the rehabilitation of Pioneer Park – a $6.3 million project intended to protect the community from flooding and improve water quality and fish habitat (Figures 4.5.3 and 4.5.4). It is the first major stormwater management rehabilitation project in Canada.
Figure 4.5.3. Pioneer Park stormwater management pond in January 2007, prior to rehabilitation project. Source: Town of Richmond Hill.
Figure 4.5.4. Pioneer Park stormwater management pond in September 2010, after rehabilitation work was completed. Source: Town of Richmond Hill.
Unfortunately, many municipalities have no stormwater monitoring programs in place and are unaware of the actual conditions of the facilities. It is very costly to monitor and maintain facilities, and to dispose of sediment. For example, if the removed sediment is contaminated it must be transported and disposed of at a certified landfill site or a hazardous waste facility. Many municipalities may not have sufficient funds set aside. During 2009/2010, MOE inspected almost 140 stormwater discharges and found that most instances of non-compliance related to insufficient monitoring.
MOE recently advised the ECO that it is working on a number of initiatives to enhance stormwater management in Ontario, including those identified in the Lake Simcoe Protection Plan and the Phosphorus Reduction Strategy, as well as a framework for sustainable stormwater management as part of rollout of the Water Opportunities Act, 2010 (for additional information on the Act, refer to Part 5.4 of this Annual Report). As of May 2011, MOE has not moved forward on any of these initiatives.
In 2010, MOE completed a three-year review of municipal stormwater management and climate change policy in response to an EBR application (for more information, refer to our 2009/2010 Annual Report).
ECO Comment
Stormwater management facilities will become increasingly important as our landscape becomes more urbanized and the effects of climate change (such as more extreme weather events) become more common. It is vital to maintain stormwater management facilities or they cease to function properly. Most municipalities, which own and operate the majority of facilities in Ontario, are not adequately inspecting, monitoring or maintaining their stormwater infrastructure. It is imperative that stormwater management facilities are not built and then forgotten. The ECO urges MOE to ensure that all stormwater management facilities, such as ponds and oil/grit separators, are sufficiently monitored and maintained. To this end, provincial guidelines could be strengthened, more stringent conditions could be added to approvals, and facilities could be better designed for maintenance.
Water management tends to be compartmentalized into distinct disciplines and separate bureaucratic entities – such as stormwater, sewage and drinking water management – rather than viewed holistically in the context of the watershed. Stormwater management facilities function much like headwater drainage features or first order streams – as originating points of river or stream flows – although these facilities are often perceived as grey infrastructure because they are constructed. While management practices have progressed in the last 20 years to include a treatment train approach, including low-impact (lot-level) development, further evolution of our thinking is needed. Many conservation authorities and municipalities are beginning to embrace the concept of integrated watershed management, which considers all components that influence hydrology. Some organizations are also asking the government to fully recognize green infrastructure in provincial policies (for more information, refer to Part 3.6 of this Annual Report). The ECO believes that water policy in Ontario should clearly recognize that stormwater management facilities and systems, while man-made, are a form of green infrastructure and part of a watershed’s hydrological function.
| Recommendation 7:
The ECO recommends that MOE require stormwater management facility owners or operators to monitor and maintain all stormwater management infrastructure in Ontario. |
For ministry comments, please see Appendix C.
| Previous section: Lakeshore Capacity Assessment: Balancing Development and Water Quality in Cottage Country |
| Next section: Before the Flood: Conservation Authorities' Vital Role in Land Use Planning |
| This is an article from the 2010/11 Annual Report to the Legislature from the Environmental Commissioner of Ontario. |
Citing This Article:
Environmental Commissioner of Ontario. 2011. "Stormwater: Our Neglected Headwaters." Engaging Solutions, ECO Annual Report, 2010/11. Toronto: The Queen's Printer for Ontario. 69-73.
