Municipal Class Environmental Assessment
Part C - Municipal Water and Wastewater Projects
C.2 DESCRIPTION OF THE PROJECTS, PURPOSE AND ALTERNATIVES
C.2.3 STORMWATER MANAGEMENT PROJECTS

C.2.3 STORMWATER MANAGEMENT PROJECTS

C.2.3.1 Description of the Projects

Stormwater management projects planned under this Class EA can generally be categorized as: 

 

A new storm sewer system may include a stormwater collection system, treatment facility(ies), an outfall/discharge/re-use/disposal facility and storage facilities. 

An expansion to an existing storm sewer system refers to the addition of sewers and new facilities or a change in management practices to an existing sewage system to increase system capacity.  

Upgrading of an existing storm sewer system consists of additions or replacements to existing sewers and facilities or implementation of practices which are intended to modify flow, volume and/or quality control. 

Watercourse management projects are intended to minimize the impacts of  flooding, erosion and bank and valley wall instabilities. 

NOTE: 

Drainage works regulated under the Drainage Act are exempt from the Ontario EA Act.

Where stormwater works are carried out in conjunction  with municipal road works, they shall be planned in accordance with the requirements of the schedules for but may be included in documentation prepared for the schedules for municipal road projects. 

Storm Sewer System Components: 

A storm sewer system will consist of the following basic components: 

The collection system collects storm drainage from such sources as private drains, road storm sewers, catch basins, ditch inlets and culverts, and conveys it to a trunk storm sewer and/or channel, which in turn conveys it to receiving waters and/or a treatment facility. 

Receiving waters and watercourses include but are not restricted to: overland flow routes, ditches, channels, intermittent or continuous streams and creeks, and rivers and lakes. 

Stormwater management and/or treatment facilities include storage and other means to achieve hydrograph attenuation, volume reduction and/or to treat and address the quality of stormwater run-off. Storage may be provided by underground chambers, roofs, parking lots and detention/retention ponds together with their outlet control structures and outfalls. Stormwater volume may be reduced by enhancing infiltration by providing infiltration wells, pipes and trenches. 

Water quality control may consist of one or more of the following: 

 

An expansion or upgrading project may include the construction of one or more of the following: 

 

Watercourse Management projects consist of works located in open watercourses and may include flood control erosion control water quality control and works related to aquatic, wildlife and terrestrial management within a floodplain

Stability Projects consist of cut and fill works in floodplains and works required to stabilize banks and valley walls where instability is not caused by watercourse flow. 

The development and implementation of a project under this Class EA will often involve additional work or activities incidental to the primary purpose of the project but which must be included in the project. These may include, for example: 

C.2.3.2 Purpose of the Project

Projects developed under this Class EA will be proposed to resolve problems affecting the operation and efficiency of existing systems and/or to accommodate future growth of communities, and/or to alleviate flooding or specific pollution problems. 

One or more of the following general objectives will be achieved: 

a) Alleviate local or regional flooding problems
b) Eliminate or reduce risk of public health or safety problems or nuisances
c) Improve the quality of effluent produced by the stormwater system
d) Expand the capacity of the stormwater system
e) Improve system or treatment efficiency
f) Prevent system failure
g) Control, erosion and sedimentation
h) Maintain baseflow or groundwater recharge
i) Reduce combined sewer overflows
j) Management of wastes produced by the system 

The purpose or objective of a specific project will be determined by existing or anticipated problem(s) affecting operation and efficiency of the system, and the present and forecast demand for increased system capacity and/or improved water quality. 

Following are descriptions of the types of problems and demands identified above: 

a) Local or Regional Flooding: 

Flooding caused by system deficiencies, alteration of land use characteristics and/or incidence of low frequency storms, may result in the following problems: 

b) Public Health and Safety: 

The well-being of human life may be affected, or nuisances may be caused, by such problems as:

 

 

c) Effluent Quality: 

The objectives for water quality include criteria governing the. physical and chemical characteristics of water bodies, (e.g. temperature, dissolved oxygen, suspended solids, grease, salts, chlorides, nutrients), microbiological criteria, and the allowable concentration of all parameters that may cause impact to receiving water quality.  The quality of the effluent produced by storm sewage systems should ensure that minimum standards set for receiving water bodies are consistently achieved. 

The rationale for an expansion or upgrading project may, therefore, be based on the current or forecast quality of effluent produced, due to such problems as: 

d) System Capacity: 

The existing storm sewage system may not be capable of handling present or forecast flows or volumes of stormwater due to such problems as: 

e) System Efficiency. 

Various facets of system efficiency such as labour, maintenance costs or energy consumption may be improved by design improvements and/or the introduction of new technology. 

f)  Potential System Failure: 

Concern may be expressed as to potential system failure due to such factors as:

g) Erosion and Sedimentation: 

Either in association with the construction of a project, and/or caused by natural processes and/or development pressures, erosion and-sedimentation may result in the following problems:

 
h) Baseflow or Groundwater Recharge: 

In areas of natural groundwater recharge, sprawling development and urbanization can threaten the continued replenishment of groundwater by precipitation and surface run-off. The following are examples of the kinds of problems which may result: 

 
i) Combined Sewer Discharges: 

During wet weather conditions, stormwater rue-off combines with sanitary sewage in combined sewers. Typical problems which result are: 

 
j) Management of Wastes: 

Failure to remove or control gravel, sand, road salt and other debris which accumulate in catch basins, retention/detention ponds, roadside ditches and in storm sewers may result in the following problems:

C.2.3.3 Alternative Solutions

There may be more than one way of solving problems or of meeting new demands on existing stormwater management systems. A number of solutions, termed “Alternative Solutions”, may include, for example: 

a) New storm sewage system.
b) Expansion or upgrading of an existing storm and/or combined sewage system.
c) Rehabilitate existing storm sewage system.
d) Expand sewer cleaning program.
e) Expand street cleaning program.
f) Remove illegal drain connections.
g) Require stormwater management.
h) Limit Community growth
i) Establish a sewer use by-law.
j) Control and/or treat combined sewer flow.
k) Manage system wastes.
1) “Do Nothing”. 

Depending on the nature of the existing stormwater management system, and on the problems being encountered or anticipated, there are various ways in which these general alternatives could be carried out. The most common of these are described below. 

In evaluating the Alternative Solutions the following factors should be kept in mind: 

For the alternative solutions identified above, a number of possible options are suggested:  

a) New Storm Sewage System:   
b) Expansion or Upgrading of Existing System:   
c) Rehabilitate Existing Storm Sewage System:  
d) Expand Sewer Cleaning Program:   
e) Expand Street Cleaning Program:   
f) Remove Illegal or Undesirable Drain Connections:   
g) Require Stormwater Management:   
h) Limit Community Growth:   
i) Establish a Sewer Use By-law:   
j) Control and/or Treat Combined Sewer Flow:   
k) Manage System Wastes:   
l) “Do Nothing”: 

In the “Do Nothing” alternative, no improvements or changes would be made to solve the identified problem(s). This means that the problems would remain in the system. It does not necessarily mean however, that no further development in the community would occur. 

The “Do Nothing” alternative shall be documented in the ESR along with any other alternative solutions which were examined.

The “Do Nothing” alternative may be implemented at any time during the design process prior to the commencement of construction. A decision to “Do Nothing” would typically be made when the costs of all other alternatives, both financial and environmental, significantly outweigh the benefits.