Conveyance Facility Design Criteria
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---|---|---|---|---|
Location
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Within Public Street Right-of-Way
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Outside Public Street Right-of-Way
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Loading
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All
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Vehicular Loading
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Non-Vehicular-Loading
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(a)
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Pipe design
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[1]
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Material
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SLHDPE, RCP
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SLHDPE, RCP
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SLHDPE, RCP
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[2]
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Slope (minimum)
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0.5%
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0.5%
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0.5%
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[3]
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Cover
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1 foot to stone subgrade
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1 foot to stone subgrade
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1 foot to surface
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[4]
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Diameter (minimum)
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18 inches
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18 inches
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18 inches
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[5]
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Street crossing angle
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90°
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90°
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N/A
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[6]
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Access/maintenance port frequency (maximum)
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400 feet
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400 feet
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400 feet
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(b)
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Inlet design
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[1]
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Material
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Concrete
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Concrete
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N/A
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[2]
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Grate depression
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N/A
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N/A
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6 inches with 20:1 approach slope
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(c)
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Manhole design
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[1]
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Material
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Concrete
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Concrete
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Concrete
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(d)
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Swale design
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[1]
|
Freeboard (minimum)
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6 inches
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N/A
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6 inches
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[2]
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Velocity (maximum)
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Stability check
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N/A
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Stability check
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[3]
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Slope (minimum)
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2%
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2%
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2%
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[4]
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Side slopes (residential area)
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4:1 max
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N/A
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4:1 max
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[5]
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Side slopes (nonresidential area)
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4:1 max
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N/A
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3:1 max
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[6]
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Bottom width to flow depth ratio
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12:1
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N/A
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12:1
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(e)
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Pipe Inlet/Outlet design
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[1]
|
End treatment
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Concrete headwall/endwall
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Headwall/endwall or flared end section
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Headwall/endwall or flared end section
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[2]
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Energy dissipater
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Required
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N/A
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Required
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Aboveground Storage Facility Design Criteria
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---|---|---|---|---|
Facility Depth
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Less than 2 feet
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2 feet to 6 feet
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Greater than 6 feet
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(a)
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Embankment Geometry
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[1]
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Top width (minimum)
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2 feet
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5 feet
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8 feet
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[2]
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Interior side slope (maximum)
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3:1
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5:1
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5:1
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[3]
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Exterior side slope (maximum)
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3:1
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3:1
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3:1
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(b)
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Embankment Construction
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[1]
|
Clay/impervious core
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Not required
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Required
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Required
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[2]
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Pipe collar
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Not required
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Required
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Required
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[3]
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Compaction density
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Not required
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Required
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Required
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(c)
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Internal Construction
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[1]
|
Dewatering feature
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N/A
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Required
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Required
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[2]
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Pretreatment elements
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Not required*
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Required
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Required
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(d)
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Outlet Structure
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[1]
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Pipe size (minimum)
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12 inches
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18 inches
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18 inches
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[2]
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Pipe material
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SLHDPE, PVC, RCP
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SLHDPE, RCP
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SLHDPE, RCP
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[3]
|
Anticlogging devices
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Required
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Required
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Required
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[4]
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Antivortex design
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Not required
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Required
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Required
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[5]
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Watertight joints in piping?
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Yes
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Yes
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Yes
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(e)
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Spillway Requirements
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[1]
|
Spillway freeboard (minimum)
|
3 inches
|
6 inches
|
12 inches
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[2]
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Width (minimum)
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5 feet
|
10 feet
|
20 feet
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[3]
|
Width (maximum)
|
20 feet
|
50 feet
|
50 feet
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[4]
|
Spillway channel design
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Required
|
Required
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Required
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[5]
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Routing of 100-year storm
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Permitted
|
Permitted
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Permitted
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NOTES:
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---|
* Pretreatment is required for infiltration BMPs unless shown
to be unnecessary.
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N/A = Not applicable.
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SLHDPE = Smooth lined high density polyethylene pipe.
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PVC = Polyvinyl chloride.
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RCP = Reinforced concrete pipe.
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Subsurface Storage Facility Design Criteria
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---|---|---|---|
Facility Type
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Infiltration and Storage
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Storage Without Infiltration
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(a)
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Facility Geometry
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[1]
|
Depth from surface (maximum)
|
2 feet less than limiting zone
|
N/A
|
[2]
|
Loading ratio (maximum)
|
Per BMP Manual*
|
N/A
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(b)
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Distribution System Requirements
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[1]
|
Pipe size (minimum)
|
4 inches
|
4 inches
|
[2]
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Loading/balancing
|
Required
|
Required
|
[3]
|
Observation/access ports
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Required
|
Required
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NOTES:
| |
---|---|
*
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Unless otherwise determined by professional geologic evaluation.
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