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)
| ||
Predevelopment Design Storm
| ||
Post-Construction Design Storm Frequency (24-Hour Duration)
|
New Development Regulated Activities
|
Redevelopment Regulated Activities
|
2-year
|
1-year
|
2-year
|
5-year
|
2-year
|
5-year
|
10-year
|
2-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
|
U.S. 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
|
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]
|
Watertight joints in piping
|
No
|
Yes
|
Yes
| ||
(e)
|
Spillway requirements
| |||||
[1]
|
Spillway freeboard (minimum)
|
Not required
|
3 inches
|
6 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
|
Notes:
|
---|
*Pretreatment required for infiltration BMPs unless shown to
be unnecessary.
|
**Spillway functions as primary control.
|
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 PA BMP Manual*
|
N/A
| |
(b)
|
Distribution system requirements
| |||
[1]
|
Pipe size (minimum)
|
4 inches
|
4 inches
| |
[2]
|
Pretreatment
|
Required
|
Required
| |
[3]
|
Loading/balancing
|
Required
|
Not required
| |
[4]
|
Observation/access ports
|
Required
|
Required
|
Notes:
| |
---|---|
*
|
Unless otherwise determined by professional geologic evaluation.
|
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
|
Notes;
|
---|
N/A = Not applicable or no criteria specified.
|
SLHDPE = Smooth lined high-density polyethylene pipe.
|
PVC = Polyvinyl chloride.
|
RCP = Reinforced concrete pipe.
|