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EA204 Environmental EA204 Environmental TechnologyTechnology
Pavement DrainagePavement Drainage
Stormwater Sewer DesignStormwater Sewer Design
Objectives of Pavement DrainageObjectives of Pavement Drainage
to collect stormwater on the surface to collect stormwater on the surface and move it into the minor system and move it into the minor system (i.e. gutters, catchbasins, ditches)(i.e. gutters, catchbasins, ditches)
to maintain a safe driving surface for to maintain a safe driving surface for the movement of trafficthe movement of traffic
Road Cross-Section: RURALRoad Cross-Section: RURAL
rural cross-sections have ditchesrural cross-sections have ditches normal crossfall is 2%normal crossfall is 2%
2.0%2.0%2.0%2.0%
Centre line (crown)Centre line (crown)
ShoulderShoulder
DitchDitch
Side SlopeSide Slope
Back SlopeBack Slope
LaneLane
Road Cross-Section: URBANRoad Cross-Section: URBAN
urban sections have curb, gutter, urban sections have curb, gutter, catchbasins, and storm sewerscatchbasins, and storm sewers
2.0%2.0%2.0%2.0%
Centre lineCentre line
Curb &Curb &GutterGutter
BoulevardBoulevard
LaneLaneSidewalkSidewalk
PropertyPropertyLineLine
Storm SewerStorm Sewer
PropertyPropertyLineLine
Minimum Pipe SizesMinimum Pipe Sizes
min diameter for storm sewers -min diameter for storm sewers -
250 mm250 mm min diameter for service leads -min diameter for service leads -
200 mm200 mm reduces chance of objects getting reduces chance of objects getting
stuckstuck enables maintenance & cleaningenables maintenance & cleaning
Minimum Cover DepthMinimum Cover Depth
below depth of frost below depth of frost penetrationpenetration
below 1.2 m to avoid below 1.2 m to avoid crushing from large crushing from large truckstrucks
below water supplybelow water supply above sanitary above sanitary
sewer systemsewer system
Flow VelocitiesFlow Velocities
Velocity in pipes is controlled by many Velocity in pipes is controlled by many elements:elements:
slopeslope
hydraulic radiushydraulic radius
roughness of pipe’s inside surfaceroughness of pipe’s inside surface
Min & Max?Min & Max?
MinimumMinimum velocities are set to prevent velocities are set to prevent sedimentation in pipessedimentation in pipes
(this would reduce pipe cross-section and (this would reduce pipe cross-section and capacity)capacity)
MaximumMaximum velocities are set to prevent velocities are set to prevent scouring and premature wear in pipesscouring and premature wear in pipes
(large objects will not be carried through (large objects will not be carried through pipes and damage them)pipes and damage them)
Manhole SpacingManhole Spacing
Stormwater sewers run in straight lines on Stormwater sewers run in straight lines on a constant slope from one manhole to a constant slope from one manhole to the next:the next:
alignment (bearing)alignment (bearing) slope (%)slope (%)
pipe size (diameter in mm)pipe size (diameter in mm) maintenance limitationsmaintenance limitations
Manhole SpacingManhole Spacing
whenever a sewer whenever a sewer changes direction changes direction (bearing) we need a (bearing) we need a manholemanhole
when the slope of a when the slope of a sewer changes we sewer changes we need a manholeneed a manhole
alignment (plan)alignment (plan)
slope (profile)slope (profile)
Manhole SpacingManhole Spacing
a manhole is a manhole is needed when we needed when we change the size of change the size of sewersewer
manholes are manholes are needed so we can needed so we can get in and clean and get in and clean and repair sewersrepair sewers
diameter (mm)diameter (mm)
maintenancemaintenance
Catchbasin & Inlet SpacingCatchbasin & Inlet Spacing
Water must be “caught” before it becomes a Water must be “caught” before it becomes a hazard:hazard:
road grade and low points (sags)road grade and low points (sags) crossfall and roadwidthcrossfall and roadwidth
design stormdesign storm pedestrian crosswalkspedestrian crosswalks
intersectionsintersections public and private drivewayspublic and private driveways
Catchbasin & Inlet SpacingCatchbasin & Inlet Spacing
steeper grades steeper grades require closer require closer spacing to keep spacing to keep velocity in gutter lowvelocity in gutter low
double inlets are double inlets are needed to handle needed to handle water from both water from both sides of sagsides of sag
road graderoad grade
low points (sags)low points (sags)
Catchbasin & Inlet SpacingCatchbasin & Inlet Spacing
inlets needed where inlets needed where water moves from water moves from crown to curb & crown to curb & guttergutter
wider roads mean wider roads mean more water and more water and closer spacingcloser spacing
crossfallcrossfall
road widthroad width
Catchbasin & Inlet SpacingCatchbasin & Inlet Spacing
higher return times higher return times mean more water mean more water and closer spacing and closer spacing to intercept waterto intercept water
inlets must be inlets must be located immediately located immediately upstream of ped upstream of ped crosswalkscrosswalks
design stormdesign storm
pedestrian pedestrian crosswalkscrosswalks
Catchbasin & Inlet SpacingCatchbasin & Inlet Spacing
inlets must be inlets must be located upstream of located upstream of intersection to intersection to prevent “rivers” prevent “rivers” flowing through flowing through intersectionintersection
inlets must be inlets must be located at least 1.5m located at least 1.5m away from drivewaysaway from driveways
intersectionsintersections
private & public private & public drivewaysdriveways
Catchbasin & Inlet Catchbasin & Inlet SpacingSpacingCross Cross
SectionSectioncc
Plan ViewPlan View
LL
CrestCrest
Min. Drive Min. Drive WidthWidth