Technical and Engineering Guidelines for Stormwater ...

1 Technical and Engineering Guidelines for Stormwater management submissions Prepared By: Ganaraska Region Conservation Authority December 2014 This page is intentionally left blank CONTENTS PAGE 1 Introduction 1 The Need for Effective Stormwater management 1 Policy Framework 2 Purpose of the Document 2 Stormwater Design Criteria 2 Ontario Regulation 168/06 3 2 Stormwater management Design Process 4 Project Scale and the Planning Process 4 Design Steps 4 Practitioner Credentials 5 Summary of Stormwater management Design Criteria 6 Fisheries Criteria 6 Erosion and Sediment Control during Construction 6 Hydraulic Considerations 6 Channelization

2 6 3 Quantity Control 7 Quantity Control Objective 7 Flood Damage Centres 7 Quantity Control Criteria 7 4 Erosion 10 Erosion Control Objective 10 Erosion Control Criteria 10 5 Quality Control 11 Water Quality Control Objective 11 Water Quality Control Criteria 11 6 Stormwater management Practices 13 Overview 13 Stormwater management Facilities 13 Submission / Review Process 13 Report Requirements for Site Plans 13 Preliminary Submission for Subdivision Draft Plan Approval 17 Detailed Submission for Subdivision 19 7 storm Infrastructure Design 23 Design Flows 23 Rainfall Intensity 23 Runoff or Impervious coefficients 23 Pipe Sizing 24 Overland Flow 24 Culvert and Bridge Hydraulic Capacity 26 Hydraulic Gradeline Calculations 26 Outlets 27 8 Stormwater management Facilities Design 28 Dry Pond Requirements 28 Wet pond Requirements 28 Wetland Requirements 28 SWM Pond Requirements 29 Post-Construction Monitoring 32 Assumption by Municipality 33 9 Sediment and Erosion Control 34 Scope 34 Procedure 34 Implementation 34 Plan Requirements 34 Construction Requirements 35 Figures Water Cycle 1 Watershed where post-development flows must be less than

3 Pre-development 7 Watershed with Normal Quality Targets 11 MH Losses 25 Shrub Density Planting 29 SWM Facility Cross-section 30 Sample SWM Pond Sign 31 Tables Calculation Recommendations 5 Water Quantity Control Requirements 8 Erosion Control Criteria 10 Quality Control Criteria 11 Modified Rational Method Calculation 15 Sewer pipe Capacity 25 MH loss coefficients 27 Appendices A Submission Check Lists B Rainfall Equations C Hydrological Values & Recommended modeling Parameters D Sample storm Sewer Design and Hydraulic Gradeline Analysis Sheets This page is intentionally left blankTechnical and Engineering Guidelines for Stormwater management submissions December 2014 Page 1 1 INTRODUCTION The Need for Effective Stormwater management Lake Ontario plays an essential role in the health and well being of residents of Northumberland County.

4 Lake Ontario provides the Town of Cobourg and the Municipality of Port Hope with a safe and abundant source of drinking water, and supports a wide range of recreational opportunities that include swimming, boating, fishing. Effective management of Stormwater is critical to the continued health of our streams, rivers, lakes, fisheries and terrestrial habitats. As can be seen in Figure below, rain can take several paths once it falls on the ground. It can infiltrate into the soil, evaporate, be subject to evapotranspiration, or it can run overland as runoff. In natural settings, vegetation and the lack of hard surfaces ensures that little runoff occurs. In urban areas with hard surfaces and limited vegetation, the majority of the rainwater becomes runoff. Source: Charles River Watershed Association Figure Water Cycle The water quality of Lake Ontario is directly dependent on the health of the rivers and creeks that feed into it.

5 Lake Ontario and its contributing watersheds can be severely impacted by human activity, particularly through the release of various pollutants into the natural environment. Human activity affects the quality and quantity of runoff. In urban areas, for example, buildings and paved streets increase the amount of hard surfaces and in turn reduce opportunities for natural infiltration. These hard surfaces decrease water quality by providing increased opportunity for pollutants to accumulate ( oil, grease, and exhaust emissions from vehicles), which are washed off during rainfall events polluting ground and surface waters. As well, hard surfaces generate increased levels of runoff, which causes downstream flooding and erosion. The increase in surface runoff may cause flooding, thus damaging property and municipal infrastructure. Water-borne pollutants can cause hydrological, water quality, and ecological impacts to natural heritage features.

6 Natural flow patterns are disrupted since rainfall is redirected Technical and Engineering Guidelines for Stormwater management submissions December 2014 Page 2 via storm sewers away from source areas to concentrated outfalls. As a result, urban areas change the natural hydrology cycle by altering the volume, frequency, duration, timing, and distribution of runoff. Policy Framework The Ganaraska Region Conservation Authority (GRCA) is a corporate body established under the Conservation Authorities Act of Ontario in October of 1946 to further the conservation, restoration, development and management of renewable natural resources. The Conservation Authorities Act requires that the GRCA prevent, eliminate, or reduce the risk to life and property from flooding and erosion, and encourage the protection and regeneration of natural systems. The GRCA works with municipalities to ensure that the tenets of the Provincial Policy Statement (PPS) are upheld, and limit effects to natural features result from development applications approved through the Planning Act.

7 Purpose of the Document The purpose of this manual is to provide a Stormwater management (SWM) planning framework, complete with associated criteria and design Guidelines , to be applied at the various stages of the planning process, ranging from Official Plan and Secondary Plan studies through to plans of subdivision and site plans. Referenced documents include: Ministry of the Environment Stormwater management Planning and Design Manual (2003) CVC/TRCA Low Impact Development Stormwater management Planning and Design Guide, Version (2010) Ministry of Transportation Drainage management Manual (1997) Golden Horseshoe CA Erosion and Sediment Control Guideline for Urban Construction (2006) The criteria used in this document are mainly based on provincial recommendations and Guidelines . In some situations, local standards or requirements may overwrite provincial Guidelines .

8 For example, identified erosion sites on a creek may necessitate a lower flow rate than provincial Guidelines . Stormwater Design Criteria Stormwater criteria shall be defined at the preliminary stages of a new planning development, and are defined to reflect the scale of studies. For example, at the watershed scale, flood control targets may consist of peak flow rates at the subwatershed outlet, while the focus at the site plan scale is on site release rates. Design criteria are provided to: Prevent increased flooding Protect water quality Preserve baseflow characteristics Limit undesirable geomorphic changes in watercourses Maintain groundwater quality Technical and Engineering Guidelines for Stormwater management submissions December 2014 Page 3 Ontario Regulation 168/06 Hazardous land (such as unstable slopes, wetlands, floodplain, etc) within the GRCA watershed is generally unsuitable for any type of development.

9 Any consideration of land development is considered on an individual basis and requires unique Engineering analysis for these following items: The straightening, changing, diverting or interfering in anyway with an existing channel, a river, creek, stream or watercourse The construction of any building or structure in or on a wetland, or in any area subject to flooding The placing of fill or dumping of fill of any kind in any defined part of the area over which the conservation authority has jurisdiction which, in the opinion of the conservation authority, the control of flooding or pollution or the conservation of land may be affected. Technical and Engineering Guidelines for Stormwater management submissions December 2014 Page 4 2 Stormwater management DESIGN PROCESS Project Scale and the Planning Process All change in land use proposed by a development application must evaluate the hydraulic, hydrologic, geomorphic, and ecological conditions of a subject area.

10 SWM designs shall address quantity, quality, and erosion controls. The scale and scope of land development ranges widely. The level of detail required to address SWM controls reflects the land use application under consideration, as described in the subsequent sections of this document. Official Plan Amendments, Secondary Plans, or Block Plans These are normally supported by a functional servicing report, a component of which includes a detailed evaluation of the subject area and its catchment(s) to derive a preliminary SWM plan. Preliminary targets and criteria are established. Zoning By-law Amendments If the change in proposed land use is significant, a SWM plan shall be created as part of a functional servicing report. Since the scale of project is more defined than at an official plan stage, a more detailed evaluation of site conditions is expected.