EA204 Environmental Technology Pavement Drainage Stormwater Sewer Design

Objectives of Pavement Drainage n to collect stormwater on the surface and move it into the minor system (i.e. gutters, catchbasins, ditches) n to maintain a safe driving surface for the movement of traffic

Road Cross-Section: RURAL n rural cross-sections have ditches n normal crossfall is 2% 2.0% 2.0% Centre line (crown) Shoulder Ditch Side Slope Back Slope Lane

Road Cross-Section: URBAN n urban sections have curb, gutter, catchbasins, and storm sewers 2.0% 2.0% Centre line Curb & Gutter Boulevard Lane Sidewalk PropertyLine Storm Sewer PropertyLine

Minimum Pipe Sizes n min diameter for storm sewers mm n min diameter for service leads mm n reduces chance of objects getting stuck n enables maintenance & cleaning

Minimum Cover Depth n below depth of frost penetration n below 1.2 m to avoid crushing from large trucks n below water supply n above sanitary sewer system

Flow Velocities n Velocity in pipes is controlled by many elements: slope hydraulic radius roughness of pipe’s inside surface

Min & Max? n Minimum velocities are set to prevent sedimentation in pipes (this would reduce pipe cross-section and capacity) n Maximum velocities are set to prevent scouring and premature wear in pipes (large objects will not be carried through pipes and damage them)

Manhole Spacing Stormwater sewers run in straight lines on a constant slope from one manhole to the next: n alignment (bearing) n slope (%) n pipe size (diameter in mm) n maintenance limitations

Manhole Spacing n whenever a sewer changes direction (bearing) we need a manhole n when the slope of a sewer changes we need a manhole n alignment (plan) n slope (profile)

Manhole Spacing n a manhole is needed when we change the size of sewer n manholes are needed so we can get in and clean and repair sewers n diameter (mm) n maintenance

Catchbasin & Inlet Spacing Water must be “caught” before it becomes a hazard: n road grade and low points (sags) n crossfall and roadwidth n design storm n pedestrian crosswalks n intersections n public and private driveways

Catchbasin & Inlet Spacing n steeper grades require closer spacing to keep velocity in gutter low n double inlets are needed to handle water from both sides of sag n road grade n low points (sags)

Catchbasin & Inlet Spacing n inlets needed where water moves from crown to curb & gutter n wider roads mean more water and closer spacing n crossfall n road width

Catchbasin & Inlet Spacing n higher return times mean more water and closer spacing to intercept water n inlets must be located immediately upstream of ped crosswalks n design storm n pedestrian crosswalks

Catchbasin & Inlet Spacing n inlets must be located upstream of intersection to prevent “rivers” flowing through intersection n inlets must be located at least 1.5m away from driveways n intersections n private & public driveways

Catchbasin & Inlet Spacing Cross SectioncPlan View L Crest Min. Drive Width