Difference between revisions of "Screening LID options"

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== Site Conditions ==
== Site Conditions ==


Complete definition of pre-development site conditions is essential prior to screening of potential stormwater BMPs. The designer should prepare maps describing site conditions and identifying all environmental features and functions that need consideration in accordance with provincial, municipal and conservation authority development regulations. This includes watercourses and small drainage features, floodplains, important recharge areas, steep slopes, wetlands, natural heritage conservation areas and significant wildlife habitats. In addition, information regarding native soil types, infiltration capacity and depth-to-water-table must be determined.
Complete definition of pre-development site conditions is essential prior to screening of potential stormwater BMPs. The designer should prepare maps describing site conditions and identifying all environmental features and functions that need consideration in accordance with provincial, municipal and conservation authority development regulations. This includes watercourses and small drainage features, floodplains, important recharge areas, steep slopes, wetlands, natural heritage conservation areas and significant wildlife habitats. In addition, information regarding native soil types, infiltration capacity and depth to water table must be determined.


In retrofit scenarios, site conditions will vary and maps can be explicit with land use type. Road right of ways, parks, residential, industrial, commercial and/or institutional should be noted.
In retrofit scenarios, site conditions will vary and maps can be explicit with land-use type. Road right of ways, parks, residential, industrial, commercial and/or institutional should be noted.


For additional information on site conditions to note for:
For additional information on site conditions to note for:
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* Maintain an appropriate diversity of aquatic life and opportunities for human uses
* Maintain an appropriate diversity of aquatic life and opportunities for human uses


The design criteria required to protect, enhance or restore the environmental resources can be grouped under the following five categories.
The design criteria required to protect, enhance or restore the environmental resources can be grouped under the following five categories:


* Flood protection
* Flood protection
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===Site constraints===
===Site constraints===


When attempting to apply stormwater BMPs within a development site, give careful consideration to site conditions and constraints. Here is a [[LID site criteria and constraints|handy table]] outlining the factors constraining use of each LID BMP.
When attempting to apply stormwater BMPs within a development site, give careful consideration to site conditions and constraints. Here is a [[LID site criteria and constraints|handy table]] outlining the factors constraining the use of each LID BMP. Further information regarding constraints to the design of various end-of-pipe BMPs can be found in the Ontario Ministry of the Environment Stormwater Management Planning and Design Manual (2003). Before resorting to end-of-pipe BMPs, evaluate whether LID BMPs can meet the design criteria.
Further information regarding constraints to the design of various end-of-pipe BMPs can be found in the Ontario Ministry of the Environment Stormwater Management Planning and Design Manual (2003). Before resorting to end-of-pipe BMPs, evaluate whether LID BMPs can meet the design criteria.


===LID opportunities and land use types===
===LID opportunities and land use types===
When working in retrofit scenarios, note that each particular land-use type has a different set of constraints on LID options. Road ROWs, residential, industrial, commercial, institutional, and park lands all provide unique opportunities and challenges:
When working in retrofit scenarios, note that each particular land-use type - road ROWs, residential, industrial, commercial, institutional, and park lands - all provide unique opportunities and challenges:


*[[LID opportunities and road types]]
*[[LID opportunities and road types]]

Revision as of 19:20, 12 December 2017

Process for selecting an individual or suite of LID Options[edit]

Process Diagram for Screening LID Options

This guidance article intends to help reduce the number of LID options in the preliminary phases of design and to alert the designer to LID opportunities unique to the site-type being assessed. When going through the process of screening LID options, it is important to have a larger contextual understanding of Integrated water management, Site design strategies, Siting and layout of development, and Link title.

Site Conditions[edit]

Complete definition of pre-development site conditions is essential prior to screening of potential stormwater BMPs. The designer should prepare maps describing site conditions and identifying all environmental features and functions that need consideration in accordance with provincial, municipal and conservation authority development regulations. This includes watercourses and small drainage features, floodplains, important recharge areas, steep slopes, wetlands, natural heritage conservation areas and significant wildlife habitats. In addition, information regarding native soil types, infiltration capacity and depth to water table must be determined.

In retrofit scenarios, site conditions will vary and maps can be explicit with land-use type. Road right of ways, parks, residential, industrial, commercial and/or institutional should be noted.

For additional information on site conditions to note for:

Define design criteria[edit]

Design criteria should be required to:

  • Preserve groundwater and baseflow characteristics
  • Prevent undesirable and costly geomorphic changes in the watercourse
  • Prevent any increases in flood risk potential
  • Protect water quality
  • Maintain an appropriate diversity of aquatic life and opportunities for human uses

The design criteria required to protect, enhance or restore the environmental resources can be grouped under the following five categories:

  • Flood protection
  • Water quality
  • Erosion control
  • Groundwater recharge
  • Natural heritage systems or green infrastructure

Screen potential LID options[edit]

Site constraints[edit]

When attempting to apply stormwater BMPs within a development site, give careful consideration to site conditions and constraints. Here is a handy table outlining the factors constraining the use of each LID BMP. Further information regarding constraints to the design of various end-of-pipe BMPs can be found in the Ontario Ministry of the Environment Stormwater Management Planning and Design Manual (2003). Before resorting to end-of-pipe BMPs, evaluate whether LID BMPs can meet the design criteria.

LID opportunities and land use types[edit]

When working in retrofit scenarios, note that each particular land-use type - road ROWs, residential, industrial, commercial, institutional, and park lands - all provide unique opportunities and challenges:

Performance requirements[edit]

Resources for evaluating LID practices within Ontario can be found at Sustainable Technologies Evaluation Program (STEP) and Credit Valley Conservation's LID Monitoring program. For a global perspective on LID performance across various geographical regions, check out the International Stormwater BMP Database. Performance data can be downloaded or uploaded and statistical analysis tools are provided.

Operations and maintenance requirements[edit]

The LID Inspection and Maintenance Guide is intended to assist municipalities and industrial/commercial/institutional (ICI) property managers with developing their capacity to integrate LID BMPs into their stormwater infrastructure programs. Part 1 of the document provides guidance on designing an effective LID BMP inspection and maintenance program, based on experiences and advice from leading jurisdictions in the United States, adapted to an Ontario context. Part 2 of the document establishes standard cold climate protocols for inspection, testing and maintenance of seven types of structural LID BMPs.

Life cycle costing[edit]

The capital and life cycle costs of seven Low Impact Development (LID) practices and seventeen design scenarios were evaluated based on a detailed assessment of input costs, maintenance requirements, rehabilitation costs and practice designs relevant to Canadian climates.The LID Life Cycle Costing Tool

Selection of suite of LIDs[edit]

LID Treatment Train Tool

In order to assess if the selected suite of BMPs effectively meet the design criteria either computer models or simple spreadsheet models should be used. Model selection will be based on the size and type of development. A wide range of simple to complex computer models such as Visual OTTHYMO, SWMM, SWMMHYNO, HSP-F andQUALHYMO are available.

Recently, the Low Impact Development Treatment Train Tool (LID TTT) has been developed by Lake Simcoe Region Conservation Authority (LSRCA), Credit Valley Conservation (CVC) and Toronto and Region Conservation Authority (TRCA) as a tool to help developers, consultants, municipalities and landowners understand and implement more sustainable stormwater management planning and design practices in their watersheds. The purpose of the tool is to analyze annual and event based runoff volumes and pollutant load removal by the use of Best Management Practices (BMP)’s and Low Impact Development (LID) techniques.

The LID TTT provides preliminary water budget analysis (i.e. surface ET, surface runoff, infiltration to soil) and pollutant load removal estimates for pre- and post-development scenarios. The tool is built upon the open source EPA SWMM5 model providing a user-friendly interface for novice modelers and cross-compatibility with SWMM5 for further model development. To download the beta version, please check out the LID Treatment Train Tool

Assess effectiveness[edit]

Once the suite of best management practices have been selected and the models have been run, a comparison of the results and the environmental design criteria can be made. An iterative approach, which involves adjusting the size or adding/deleting BMPs should be used until the environmental design criteria are met. The LID Treatment Train Tool can help with adjusting the size of the features to see if criteria are met. Once met, the project can then proceed to the detailed design stage.