MEDIA BACKGROUNDER: Green Cities, Great Lakes

Combined sewer system: antiquated system that transports both sanitary sewage and stormwater in the same pipe.

CSO - During wet weather events (e.g. rainstorms) the volume of flow commonly exceeds the capacity of the sewer system, causing untreated raw sewage mixed with stormwater to be released directly into local water bodies from outfalls referred to as combined sewer outfalls. This release is called a combined sewer overflow (CSO).

Bypass - When a sewage facility is overloaded during wet weather, routine maintenance activities, and power failures, some sewage flow is deliberately redirected and discharged into local water bodies with little or no treatment.

The antiquated sewer systems in many Great Lakes cities regularly release huge quantities of partially treated or untreated sewage directly into adjacent water bodies through bypasses and CSOs.

The Great Lakes Sewage Report Card released by Ecojustice (then Sierra Legal) in November 2006 surveyed twenty cites in the Great Lakes basin and found that 92 billion litres of raw sewage mixed with stormwater were released into the Great Lakes in one year by those cities alone via CSOs.

According to information obtained from the province of Ontario there are 107 combined sewer systems in 89 Ontario municipalities.

CSOs and bypasses are not publicly reported in Ontario, and it is therefore difficult to obtain a complete picture of the extent of the problem

Hard infrastructure (eg. pipes, storage tunnels, tanks) targets the end-of-pipe rather than the source of the problem – excessive stormwater runoff entering combined sewer systems.

A 2005 report estimated that Ontario’s water and wastewater infrastructure would need an investment of $30 to $40 billion over the following 15 years for repairs and upgrades.

Since hard infrastructure is costly and difficult to incorporate into highly developed urban areas, many cities are left looking for other options, such as green infrastructure.

Definition: the network of urban forests, wetlands, waterways and other areas that maintain natural ecological processes, as well as engineered human-designed systems that mimic nature in function, such as green roofs.

Function: manages stormwater at the source by capturing stormwater runoff and retaining it before it can reach the sewer system. This relieves the strain on hard infrastructure, which limits the frequency of CSOs and reduces the volume of polluted stormwater runoff entering local water bodies.

Reducing the amount of stormwater generated at the source is generally less costly than constructing pipes and increasing capacity at treatment plants, particularly when major infrastructural improvements are required.

Localized, site-specific practices, such as green roofs, downspout disconnections, rain gardens, and porous pavements are designed to maintain natural hydrologic functions for individual sites by absorbing and infiltrating precipitation where it falls:

Green Roof: vegetated area built onto a building's roof to retain rainfall that allows for on-site filtration, and a slower rate and reduced volume of stormwater runoff.

Downspout Disconnection: disconnection of a building's roof drainage system from the sewer system and redirection of runoff either onto lawns or gardens or into rain barrels or cisterns to be captured for re-use.

Permeable Pavement: often used in parking lot designs, and frequently built with an underlying stone reservoir to temporarily store surface runoff before it infiltrates into the subsoil, it can provide for long-term stormwater management if properly maintained. Examples include permeable asphalt, concrete or interlocking concrete pavers.

Bioretention Area: shallow landscaped depressions, such as rain gardens, vegetated buffers, and swales, they are commonly located in parking lots or residential sidewalk areas to absorb stormwater runoff. One of the few retrofit options in highly urbanized areas.

Site-specific green infrastructure can be integrated across a community to comprise a system of green street design elements. Street-scale practices involve innovative street planning with space for road swales, bioretention areas, vegetated curb extensions, and street trees to filter and store stormwater. These ‘green streets’ are designed to maximize the use of permeable and vegetated surfaces and the ability of the street’s tree canopy to capture stormwater.

Green infrastructure can also be used on a regional basis through conservation and protection of natural spaces, which includes networks of parklands, ravines, urban forest areas and wetlands. Street trees (collectively referred to as the urban forest) can reduce stormwater runoff by intercepting rainfall on leaves and branches before it hits the pavement. Wetland and stream restoration projects reduce the strain on stormwater and combined sewer systems while improving water quality and wildlife habitat.

Toronto: Toronto's stormwater is a leading cause of pollution in Lake Ontario. As a result, the City has a downspout disconnection program (mandatory as of 2007), and the Green Roof Incentive Program, which offers grants of up to $20,000 for property owners to plant vegetation on building roofs (Toronto currently has over 100 green roofs). Toronto's Green Development Standards for stormwater management for sustainable site or building design (mandatory for City-owned properties), are set to minimize, manage and clean the stormwater that leaves a site.

St. Catharines: the City has a downspout disconnection program, subsidized rain barrels are offered to the public, and rain gardens are encouraged in residential areas through a public education and outreach program. In 2008, the City will commission a new constructed wetland to treat stormwater runoff.

London: stormwater management is required for all new developments, downspouts are not permitted to be connected to the sanitary sewer system, and the City is developing a Green Infrastructure Plan to incorporate natural systems into design standards to improve water quality and reduce overland runoff

Incorporate green infrastructure into development planning, and revise policies which discourage its use (i.e. building codes) to include provisions for green development standards.

Ecojustice, formerly Sierra Legal Defence Fund, is Canada’s leading non-profit organization of lawyers and scientists devoted to protecting the environment. Since 1990, we have helped hundreds of groups, coalitions and communities expose law-breakers, hold governments accountable and establish powerful legal precedents in defence of our air, water, wildlife and natural spaces.