REGION OF PEEL PUBLIC WORKS DESIGN, SPECIFICATIONS & PROCEDURES MANUAL LINEAR INFRASTRUCTURE Storm Sewer Design Criteria REVISED July 2009
PUBLIC WORKS STORM SEWER DESIGN CRITERIA TABLE OF CONTENTS 1.0 INTRODUCTION...1 2.0 GENERAL...1 3.0 DRAINAGE...2 4.0 DESIGN FLOWS...2 5.0 PIPE SPECIFICATIONS...3 6.0 MAINTENANCE HOLES...4 7.0 CATCHMENT POINTS...5 8.0 STORM LATERALS...6
Page: 1 1.0 INTRODUCTION Designs of municipal services in the Region of Peel are to be based upon the current Public Works Design, Specification & Procedures Manual. All plans are to be reviewed and accepted by the Region prior to construction of services. Such Regional acceptance of drawings shall not relieve the designer from primary responsibility for the design to meet all Federal, Provincial, Regional and local government requirements and/or codes. 1.1 Geotechnical Investigation The designer and/or Regional staff shall determine the need for soils investigation. The purpose of an investigation would be to determine the soil composition, bearing strength and type, and to verify that no contamination is present. Pavement design will also be required where applicable. 2.0 GENERAL Region of Peel storm sewers are generally designed to convey run-off from the Right-of-Way of a Regional Road only. Where possible, flows from outside the Regional road allowance are to be directed to the local municipality s storm sewer system. In case of: (i) Rural road - ditches and corrugated steel culverts (or approved equivalents) shall be provided for conveyance of storm water flow to outlet(s). (ii) Urban road with curbs and gutters - provide storm sewers and catchment points equipped with catchbasins. No grading will be permitted within any Region of Peel Right-of-Way to support adjacent development.
Page: 2 3.0 DRAINAGE All external lands that drain to a Regional storm sewer must conform to the following rule; Post-Development flows must be equal to or less than Pre- Development levels Flows are to be designed as per section 4.0 DESIGN FLOWS. A storm water management report may be required, illustrating appropriate storm water management techniques and design flows, please refer to the Functional Servicing & Storm Water Management Report section of the Environment, Transportation and Planning Services Design Specifications & Procedures Manual for additional information. 4.0 DESIGN FLOWS Storm sewers are to be designed using the local municipality s intensity, duration and frequency rainfall curves for a 10-year storm with 15 minute inlet time for the roadway right of way only. In the event the storm water catchment area includes areas beyond the right of way, the inlet time shall be calculated using the local municipality drainage calculation sheets and appropriate rainfall intensity tables. Post-Development flows must be equal to or less than Pre- Development levels. Methods of quantity and quality control shall be based on established storm water management practices. Typical storm water storage methods include but are not limited to parking lot storage, rooftop storage, SWM ponds and oversized infrastructure. Pipe sizing shall be for full flow with a minimum velocity of 0.75 metres per second and a maximum velocity of 3.5 metres per second.
Page: 3 5.0 PIPE SPECIFICATIONS The following specifications are guidelines only; reconstruction projects may require alternate locations and design specifications. 5.1 Location Storm sewers shall be located as per local municipality s standard cross sections, generally 1.50m south or west of the centerline of the road allowance unless conflicts with other utilities require a revised location. A 2.0m horizontal separation between the sanitary sewer and storm sewer will be permitted to allow for common trench construction as long as the inverts of both sewers are relatively at the same elevation. Should the sewer inverts vary by more than 1.0 meter, a 3.0 meter separation shall be maintained. 5.2 Depth Storm sewers shall be installed at a minimum depth of 1.5m cover below centerline of the road to obvert of the pipe. Less than 1.5m cover will be considered on industrial sites. 5.3 Bedding Storm sewers shall be installed with bedding as per Region Standard Drawing 2-3-1. 5.4 Materials Pipe material shall be as per the latest Region of Peel material specifications and standard drawings. Maintenance holes, stormceptors and catchbasins shall be as per O.P.S.D. standards.
Page: 4 6.0 MAINTENANCE HOLES Storm maintenance holes shall conform to current O.P.S.D. standards. Although these standards provide details for maintenance holes up to certain maximum depths and sizes, the Consulting Engineer shall analyze, individually, each application of the standards related to soil conditions, loading and other pertinent factors to determine structural suitability. In all cases where the standards are not applicable, the maintenance hole shall be individually designed and detailed. A reference shall be made on all profile drawings to the type and size of storm maintenance holes. All storm maintenance holes shall adhere to the following criteria: a) Maximum spacing shall be 120 m between maintenance holes for sewers up to 600mm diameter. For sewers greater than 600mm diameter spacing up to 170 metres may be used. b) Drops through storm maintenance holes shall be calculated using the following formula: Velocity Head = 2 V 2g 90 o bends = ½ Velocity Head 45 o bends = ¼ Velocity Head Where: g = 9.8 m/sec 2 c) At maintenance holes where pipe sizes change, the above criteria shall be altered such that the obverts of the pipe are matched. d) Where depth from the invert to top of a maintenance hole exceeds 5.0 m, a safety platform is to be provided as per Regional Standard 2-2-1. The platform shall be located to allow 2.0 m below manhole cover and 2.6 m above benching. e) Drop maintenance holes shall be provided where the difference in invert elevation is greater than 1.2m. The drop pipe shall be one size smaller than the sewer line (minimum 250mm diameter). The economic feasibility of providing a deeper storm sewer instead of a drop maintenance hole shall be explored. The use of 45 o bends and Y s for drops is acceptable.
Page: 5 f) When a PVC sewer is installed into a maintenance hole, one of the following methods is to be used: i) Couplings providing an elastomeric gasket seal are to be grouted into the maintenance hole wall. ii) A manufactured length of PVC pipe that has been softened with solvent and covered with sand for adherence to grout in the maintenance wall. h) The maximum distance to the first joint from the maintenance hole wall when using PVC pipe shall be 0.60 m (see diagram). Special care shall be taken in compacting the over-excavated area at the maintenance hole wall. As an alternative, concrete fill may be used to 100 mm below the sewer invert. Standard bedding is then used for the remainder. i) As per Regional Standards storm sewer maintenance holes shall be benched to the obvert of the outlet pipe on a vertical projection from the springline of the sewer. STD DWG 2-1-4. 7.0 CATCHMENT POINTS a) Catch basins shall be selected, located and spaced in accordance with conditions of design; the spacing shall not exceed 75m. The design for catch basin location and type shall take into consideration the lot areas, lot grades, road widths and road grades. Double catch basins are required at sag locations where drainage is received from more than one direction.
Page: 6 b) Road grading shall be assessed for efficient drainage of storm water to provide safe passage of vehicles. b) At street intersections, catch basins shall be located immediately upstream of sidewalk or pedestrian crosswalks. c) Catch basins and connections shall provide for the expected maximum flow. d) OPSD-400.081 (latest version), Cast Iron, Curb Inlet Frame with Two Piece Raised Cover for Catch Basins shall be used. When design will not permit a side inlet catch basin, OPSD-400.100 (latest revision), Cast Iron, Square Frame, with Square Flat Grate for Catch Basins, Perforated Openings shall be used. 8.0 STORM LATERALS 8.1 Residential All residential connections shall be in accordance with the current Manufacturer s Approved Products list, Wastewater. The minimum diameter within the road allowance shall be 125 mm for a single connection and 150 mm for a double connection. If necessary, risers shall be provided for connection with the main sewer as per STD DWG. 2-4-1 to 2-4-3. These risers are to be shown on the profile portion of the drawings. Grades of 1% minimum shall be used for laterals. Connections directly into maintenance holes shall be minimized and reviewed on an individual basis. 8.2 Commercial In commercial areas, the maximum connection size shall be 250 mm in diameter, installed with a minimum grade of 1%. The maximum drop across the property line manhole shall be 0.03 m. The maximum depth is as required by design. A maintenance hole will be required if the lateral diameter is equal to or greater than half the diameter on the main line sewer, except for a 150 mm diameter pipe connecting to (connection to) a 250 mm diameter mainline or a 200mm diameter pipe connecting to (connection to) a 375 mm diameter (see matrix below). If necessary, risers shall be provided at the main sewer and shown on the profile drawings as per STD
Page: 7 DWG. 2-4-1 to 2-4-3. Connection numbers are to be established prior to construction of the lateral. Pipe materials shall be in accordance with the current Manufacturer s Approved Products List, Wastewater. 8.3 Industrial The maximum connection size shall be 250 mm diameter, installed on a minimum grade of 1%. The maximum drop across the property line manhole shall be 0.03 m. A maintenance hole will be required if the lateral diameter is equal to or greater than half the diameter on the main line sewer, except for a 150mm diameter pipe connecting to a 250mm diameter mainline or a 200mm diameter pipe connecting to a 375mm diameter mainline (see matrix below). If necessary, risers shall be provided at the main sewer and shown on the profile drawings as per STD DWG. 2-4-1 to 2-4-3. Connection numbers are to be established prior to construction of the lateral. Pipe materials shall be in accordance with the current Manufacturers Approved Products List, Wastewater. Maintenance Hole Requirements Matrix MH required = Y MH not required = N Lateral 150 mm ø 200 mm ø 250 mm ø Mainline Sewer 250 mm ø N Y Y 300 mm ø N Y Y 375 mm ø N N Y 450 mm ø N N Y 9.0 CROSSINGS Storm crossings under a Regional Road shall meet the following criteria: Storm sewers and culverts that cross the roadway are to be designed for a 25 year storm with a 10 minute inlet time.
Page: 8 Driveway Minimum 375mm diameter (inside diameter) Roadway Minimum 600mm diameter Major crossings are to be designed for a regional storm event and a HECII analysis may be required. Prior to storm sewer design, advise the affected area municipality of the proposed design and obtain confirmation of acceptability of the design criteria. In an event area municipality design criteria is higher, design storm sewers to meet their requirements.