LOW IMPACT DEVELOPMENT INTERIM GUIDANCE DOCUMENT

Transcription

1 2017 LOW IMPACT DEVELOPMENT INTERIM GUIDANCE DOCUMENT 1

2 Low Impact Development Interim Guidance City of Barrie 1 Introduction This document was prepared to provide interim design guidance and the requirements of the City of Barrie (City) regarding Low Impact Development (LID) practices within storm drainage and stormwater management. Over time it will be necessary to update this interim guidance document as the regulations, design practices and technologies continue to evolve and change. The guidance within this document is based on current industry standard practices (e.g. Lake Simcoe Region Conservation Authority Technical Guidelines for Stormwater Management Submissions, MOECC and Credit Valley Conservation Authority Low Impact Development Design Guidance) and the specific needs and requirements of the City of Barrie. 1.1 Purpose and Application The information within this document is intended as a guide for LID implementation within storm drainage and stormwater management design, to establish a baseline for minimum standards, and to guide best practice engineering. Each proposed LID implementation will be reviewed on a case by case basis through established processes. Deviations which improve or provide equivalent results will be considered and must be approved by the City of a case by case basis In situations where this guidance does not align with current Storm Drainage and Stormwater Management Policies and Design Guideline, this document will take precedence. Changes and revisions to this document may be made from time to time and it is the responsibility of the Designer to obtain and make use of the latest version available at the time of engineering design. This document is not intended to provide guidance on the selection of LID technologies required to meet specific drainage or environmental objectives. 1.2 Application of Low Impact Development Facilities on Private Lands The City is not in the practice of prescribing specific solutions on private property, and does not intend to monitor, inspect, maintain or otherwise enforce implementation or operation of LID facilities on private property, except where may be required to ensure compliance with City by-laws, including but not limited to the Sewer Use By-Law and/or Site Alteration By-Law. However, the implementation of lot level control within private property, both residential and ICI, has been generally recommended as per the City's Comprehensive Stormwater Management Master Plan (November 2016). Designers should be critical of their selection of LID facilities used for lot level control, ensuring that they; Are difficult to remove or otherwise compromise Provide pre-treatment to the greatest extent possible Are designed to provide a maximum asset lifespan Require minimal maintenance that does not require effort or resources outside of the scope of the anticipated owner Provide for monitoring devices as required Mitigate potential impacts/ nuisance issues (basement moisture / flooding etc.) 2

3 Low Impact Development Interim Guidance City of Barrie 1.3 Source Water Protection Source water protection focuses on actions taken to protect current and future municipal drinking water sources from overuse and contamination as a requirement of the Clean Water Act. The City screens proposed Works to identify those that are located in proximity to, or whose activities may impact, municipal drinking water sources. When necessary the City will contact the Developer to discuss any requirements that pertain to the proposed Works. The City has prepared a screening document that outlines a decision making framework for determining the suitability of an infiltration LID feature in relation to Drinking Water Source Protection considerations. This document is available on the City s webpage. 3

4 Semi-Linear / Centralized Location Opportunities Parks NHS Buffer Adjacent to ROW Implementation Guidance implementation of LID infrastructure in parks will only be considered where the proponent can demonstrate implementation will reduce the need for linear LID infrastructure within the ROW for new development, maximizing upstream catchment size should be considered in selecting park locations target the first 15m of NHS buffer abutting development open space area that is not significantly treed (agriculture lands in current conditions) adjacent to standard road ROWs in linear storm block locations with sufficient setback (industrial, commercial, institutional) and roads through park areas or natural areas not acceptable in residential areas Recommend LID Practice underground underground alternative proposals will be reviewed provided they are low maintenance and non-ornate Potential location for End-of-pipe LID treatments underground infiltration trench City of Barrie - Draft LID Assessment Table Pre-Treatment Flushing Provisions Access Requirements Special Considerations OGS device 3 first flush capture operations Other pre-treatment facilities may be considered within park spaces if facility can meet the performance level provided by OGS OGS device 3 first flush capture operations 1,2 catchment area > 0.5 ha, provide OGS device 3 catchment area < 0.5 ha, utilize devices and pretreatment baffles (locate immediately upstream of flushing access MH) first flush capture operations 1,2 NOTE: 1 - if feasible, 2 - applies only to, 3-50% TSS removal per ETV testing provide dedicated MH for flushing access 2 provide inspection ports for every chamber row at start, end and every 25m in length with cast iron surface lids provide dedicated MH for flushing access 2 provide dedicated MH for flushing access 2 provide inspection ports at start of every chamber row, end and every 25m in length with cast iron surface lids 2 infiltration trench - provide upstream and downstream flushing access via MH provide an access road per City standard or alternatively, locate maintenance access points within parking areas if applicable provide an access road per City standard or alternatively, locate maintenance access points within parking areas if applicable provide a curb cut and asphalt driveway to primary maintenance access point adequate depth of cover is required for surface irrigation park use cannot be impacted by LID infrastructure LID may be placed under passive areas within park lands locations under active playing areas may be considered if no other suitable location is feasible surface structures shall be located outside of playground areas and play out limits as per City BSDs LID infrastructure proposed within the NHS buffer shall be coordinated with LSRCA/NVCA at early conceptual design stage to ensure location is suitable LID infrastructure must be accessible for operations and maintenance, as part of the design, ensure equipment required for maintenance can access all required areas zoning requirements encouraging reduced or zero setback may limit implementation opportunities not suitable when conflicts with overhead hydro installations are identified September 2017 i

5 City of Barrie - Draft LID Assessment Table Semi-Linear / Centralized Linear Location Opportunities Window Streets End-of-Pipe LID Enhancement s for Traditional SWM Roads - Infiltration System Under Boulevard Implementation Guidance location between local roads and collector roads; typically straddling property line enhancements to traditional flood control / centralized SWM facilities implementation of LID infrastructure within the ROW is only when opportunities private and semilinear/centralized have been exhausted Recommend LID Practice underground infiltration trench turf bioretention if infiltration practices are not feasible Examples include: dry pond to wet land dry pond to infiltration cell wet pond to infiltration cell dry pond to infiltration cell under dry pond linear underground chamber (preferred) or alternative that do not require confined space entry for maintenance activities Pre-Treatment catchment area > 0.5 ha, provide OGS device 3 catchment area < 0.5 ha, sediment capture devices and pre-treatment baffles (locate immediately upstream of flushing access MH) first flush capture operations 1,2 OGS device 3 wet ponds to wetland hybrid to include a standard forebay All CBs to include deeper sumps with devices and pretreatment baffles in MHs (pre-treatment baffle). MHs shall include sumps designed as required per the product employed 1 - if feasible, 2 - applies only to, 3-50% TSS removal per ETV testing Flushing Provisions provide dedicated MH 2 for flushing access provide inspection ports at start of every chamber row, end and every 25m in length with cast iron surface lids 2 infiltration trench - provide upstream and downstream flushing access MH dependent on practice flushing shall be accomplished without the need for confined space entry maximum MH spacing per City of Barrie SWM standards geotextile provided for chamber to be suitable for yearly flushing for the asset life Access Requirements provide an asphalt/limestone screenings access road per City standard or alternatively, locate maintenance access points within park parking areas if applicable as per City standards for SWM facility maintenance locate access MHs to allow vacuum truck to park in the curb lane Special Considerations maintenance access should be from the local road for bioretention utilize curb cut with concrete splash pad wetland element must be designed for long service life without significant intervention to maintain plantings sediment must be captured in OGS device; forebay within wet pond cell considered as failsafe to protect wetland from sediment deposition infiltration gallery must be protected from sediment; asset life shall mimic the design life of the roadway inspection ports suitable for the installation surface (road or boulevard) are required minor system conveyance capacity must be maintained should be designed to avoid receiving runoff from intersections due to spills associated with vehicular collisions September 2017 ii

6 City of Barrie - Draft LID Assessment Table Location Opportunitie s Implementation Guidance Recommend LID Practice Pre-Treatment Flushing Provisions Access Requirements Special Considerations Linear Roads - Infiltration System Under Asphalt Filtration implementation of LID infrastructure within the ROW is only when opportunities private and semi-linear/centralized have been exhausted filtration based practices are ideally suited for ICI or condominium development parking lots (bioretention cells in parking islands / site landscaping), as part of end-of-pipe SWM Facility Enhancements or as part of source control LIDs only considered if opportunities private, semi-linear/centralized and roadway infiltration facilities have been exhausted restricted to local roads only that generate clean runoff and receive minimal winter maintenance (minimum 100m from intersections and horizontal/vertical curves, flat grading only linear underground chamber system enhanced grass swales or turf bioswales only (municipal ROW) All CBs to include deeper sumps with devices and pretreatment baffles in MHs. MHs shall include sumps designed as required per the pre-treatment baffle product employed no ability to pretreat surface drainage to surface LID flushing shall be accomplished without the need for confined space entry maximum MH spacing per City of Barrie SWM standards geotextile provided for chamber to be suitable for yearly flushing for the asset life filtration practices generally cannot be flushed locate access MHs to allow vacuum truck to park in the curb lane typically located in boulevards asset life shall mimic the life cycle of the roadway minor system conveyance capacity must be maintained City will not accept which require confined space entry for maintenance inspection ports suitable for the installation surface (road or boulevard) are required vehicle loading shall be taken into consideration when selecting the product and infrastructure alignment location (may not be suitable for arterial/collector roads) Filtration based LID would be acceptable for installation within the ROW, provided the following issues are considered and/or mitigated: Sufficient ROW width (local, collector and arterial) is available Maximum asset life is achievable with minimal maintenance and appropriate pretreatment/removal of annual winter sand accumulation Sufficient clearance from adjacent utilities maintained to limit increased probability of damaging/destroying adjacent infrastructure Limit the amount of contaminated material requiring disposal impervious to practice area ratio for collector and arterial roads managed, preventing system overload / flow cutting 1 - if feasible, 2 - applies only to, 3-50% TSS removal per ETV testing September 2017 iii