Table 308.1
| |||
---|---|---|---|
Peak Rate Control Standards
| |||
(Peak Flow Rate of the Post-Construction Design Storm
Shall be Reduced to the Peak Flow Rate of the Corresponding Predevelopment
Design Storm Shown in the Table)
| |||
Post-Construction Design Storm Frequency (24-hour duration)
|
Predevelopment Design Storm
| ||
New Development Regulated Activities
|
Redevelopment Regulated Activities
| ||
2-year
|
1-year
|
2-year
| |
5-year
|
5-year
|
5-year
| |
10-year
|
10-year
|
10-year
| |
25-year
|
25-year
|
25-year
| |
50-year
|
50-year
|
50-year
| |
100-year
|
100-year
|
100-year
|
Table 309.1
| |||
---|---|---|---|
Acceptable Computation Methodologies for SWM Site Plan
| |||
Method
|
Developed By
|
Applicability
| |
TR-20 (or commercial computer package based on TR-20)
|
USDA NRCS
|
Applicable where use of full hydrology computer model is desirable
or necessary
| |
TR-55 (or commercial computer package based on TR-55)
|
USDA NRCS
|
Applicable for land development plans where limitations described
in TR-55 are met
| |
HEC-1/HEC-HMS
|
US Army Corps of Engineers
|
Applicable where use of a full hydrologic computer model is
desirable or necessary
| |
Rational Method (or commercial computer package based on Rational
Method)
|
Emil Kuichling (1889)
|
For sites up to 5 acres, or as approved by the municipality
| |
Other methods
|
Varies
|
Other computation methodologies approved by the municipality
|
Conveyance Facility Design Criteria
| |||||
---|---|---|---|---|---|
Location
|
Within Public Street Right-of-Way
|
Outside Public Street Right-of-Way
| |||
Loading
|
All
|
Vehicular Loading
|
Nonvehicular Loading
| ||
A.
|
Pipe design
| ||||
(1)
|
Material
|
SLHDPE, RCP
|
PVC, SLHDPE, RCP
|
PVC, SLHDPE, RCP
| |
(2)
|
Slope (minimum)
|
0.5%
|
0.5%
|
0.5%
| |
(3)
|
Cover
|
1 foot to stone subgrade
|
1 foot to stone subgrade
|
1 foot to surface
| |
(4)
|
Diameter (minimum)
|
15 inches
|
15 inches
|
8 inches
| |
(5)
|
Street crossing angle
|
75° to 90°
|
N/A
|
N/A
| |
(6)
|
Access /maintenance port frequency (maximum)
|
400 feet
|
400 feet
|
600 feet
| |
B.
|
Inlet design
| ||||
(1)
|
Material
|
Concrete
|
Concrete
|
N/A
| |
(2)
|
Grate depression
|
2 inches
|
2 inches
|
1 inch minimum
| |
C.
|
Manhole design
| ||||
(1)
|
Material
|
Concrete
|
Concrete
|
Concrete
| |
D.
|
Swale design
| ||||
(1)
|
Freeboard (minimum)
|
6 inches
|
N/A
|
6 inches
| |
(2)
|
Velocity (maximum)
|
Stability check
|
N/A
|
Stability check
| |
(3)
|
Slope (minimum)
|
1%
|
N/A
|
1%
| |
(4)
|
Side slopes (residential area)
|
4:1 max
|
N/A
|
4:1 max
| |
(5)
|
Side slopes (nonresidential area)
|
4:1 max
|
N/A
|
3:1 max
| |
(6)
|
Bottom width to flow depth ratio
|
12:1
|
N/A
|
12:1
| |
E.
|
Outlet design
| ||||
(1)
|
End treatment
|
Headwall/endwall
|
N/A
|
Headwall/ endwall or flared end section
| |
(2)
|
Energy dissipater
|
Required
|
N/A
|
Required
|
KEY:
|
---|
N/A = Not applicable or no criteria specified.
|
SLHDPE = Smooth lined high-density polyethylene pipe.
|
PVC = Polyvinyl chloride.
|
RCP = Reinforced concrete pipe.
|
Aboveground Storage Facility Design Criteria
| |||||||||
---|---|---|---|---|---|---|---|---|---|
Facility Depth
| |||||||||
Less than 2 Feet
|
2 Feet to 8 Feet
|
Greater Than 8 Feet
| |||||||
A.
|
Embankment Geometry
| ||||||||
(1)
|
Top width (minimum)
|
2 feet
|
5 feet
|
8 feet
| |||||
(2)
|
Interior side slope (maximum)
|
2:1
|
3:1
|
5:1
| |||||
(3)
|
Exterior side slope (maximum)
|
2:1
|
3:1
|
3:1
| |||||
B.
|
Embankment construction
| ||||||||
(1)
|
Key trench
|
Not required
|
Required
|
Required
| |||||
(2)
|
Pipe collar
|
Not required
|
Required
|
Required
| |||||
(3)
|
Compaction density
|
Not required
|
Required
|
Required
| |||||
C.
|
Internal Construction
| ||||||||
(1)
|
Dewatering feature
|
N/A
|
Required
|
Required
| |||||
(2)
|
Pretreatment elements*
|
Not required
|
Required
|
Required
| |||||
D.
|
Outlet Structure
| ||||||||
(1)
|
Pipe size (minimum)
|
6 inches
|
12 inches
|
15 inches
| |||||
(2)
|
Pipe material
|
SLHDPE, PVC, RCP
|
SLHDPE, RCP
|
RCP
| |||||
(3)
|
Anticlogging devices
|
Required
|
Required
|
Required
| |||||
(4)
|
Antivortex design
|
Not required
|
Required
|
Required
| |||||
(5)
|
Water-tight joints in piping?
|
No
|
Yes
|
Yes
| |||||
E.
|
Spillway Requirements
| ||||||||
(1)
|
Spillway freeboard (minimum)
|
Not required
|
6 inches
|
12 inches
| |||||
(2)
|
Width (minimum)
|
Not required
|
10 feet
|
20 feet
| |||||
(3)
|
Width (maximum)
|
Not required
|
50 feet
|
50 feet
| |||||
(4)
|
Spillway channel design
|
Not required
|
Required
|
Required
| |||||
(5)
|
Routing of 100-year storm
|
Permitted
|
Permitted
|
Permitted
|
KEY:
| ||
---|---|---|
*
|
Pretreatment required for infiltration BMPs unless shown to
be unnecessary.
| |
N/A = Not applicable.
| ||
SLHDPE = Smooth lined high-density polyethylene pipe.
| ||
PVC = Polyvinyl chloride.
| ||
RCP = Reinforced concrete pipe.
|
Subsurface Storage Facility Design Criteria
| |||||
---|---|---|---|---|---|
Facility Type
| |||||
Infiltration and Storage
|
Storage without Infiltration
| ||||
A
|
Facility Geometry
| ||||
(1)
|
Depth from surface (maximum)
|
2 feet less than limiting zone
|
N/A
| ||
(2)
|
Loading ratio (maximum)
|
Per BMP Manual*
|
N/A
| ||
B.
|
Distribution System Requirements
| ||||
(1)
|
Pipe size (minimum)
|
4 inches
|
4 inches
| ||
(2)
|
Loading/balancing
|
Required
|
Not required
| ||
(3)
|
Observation/access ports
|
Required
|
Required
|
NOTES:
| ||
---|---|---|
*
|
Unless otherwise determined by professional geologic evaluation.
|