WQv
|
=
|
(1.2) (Rv)(A)
| ||
---|---|---|---|---|
|
P = 1.53 inches of rainfall
| |||
12
|
Where:
| ||
---|---|---|
WQv = water quality volume
(in ac-ft)
| ||
Rv = 0.05 + 0.009(I)
where I is percent impervious cover
| ||
A = area in acres*
|
*Treatment of the WQv for off-site areas and areas not disturbed is not required.
|
Table 302-1: Stormwater Hotspots
| |
---|---|
Vehicle salvage yards and recycling facilities*
| |
Vehicle service and maintenance facilities
| |
Vehicle and equipment cleaning facilities*
| |
Fleet storage areas (bus, truck, etc.)*
| |
Industrial sites
| |
Marinas (service and maintenance)*
| |
Outdoor liquid container storage
| |
Outdoor loading/unloading facilities
| |
Public works storage areas
| |
Facilities that generate or store hazardous
materials*
| |
Commercial container nursery
| |
Golf courses
| |
Other land uses and activities as designated
|
NOTES:
| |
---|---|
*Stormwater Pollution Plan implementation may
be required for these land uses or activities under the U.S. EPA NPDES
stormwater program.
|
Rev = [(S)(Rv)(A)]/12
|
Where:
| ||
---|---|---|
Rv = 0.05 + 0.009(I)
where I is percent impervious cover
| ||
A = site area in acres
|
Rev = (S)(Ai)
|
Where:
| ||
---|---|---|
Ai = the measured impervious
cover
|
Hydrologic Soil Group
|
Soil Specific Recharge Factor (S)
| |
---|---|---|
A
|
0.40
| |
B
|
0.27
| |
C
|
0.14
| |
D
|
0.07
|
Two-year post-development peak flow rate
|
<=
|
One-year pre-development peak flow rate
|
Five-year post-development peak flow rate
|
<=
|
Two-year pre-development peak flow rate
|
Table 305-1: Bull Run Watershed Release
Rates
| |||
---|---|---|---|
Subareas
|
Release Rate
(%)
| ||
Bull Run Watershed
|
1
|
80
| |
2
|
50
| ||
3
|
100
| ||
4
|
100
| ||
5
|
60
| ||
6
|
60
| ||
7
|
100
| ||
8
|
70
| ||
9
|
50
| ||
10
|
60
| ||
Miller Run
|
37-40
|
100
| |
42-45
|
100
| ||
46
|
75
| ||
47
|
100
| ||
49-51
|
100
|
Table 305-2: Buffalo Creek
| ||||
---|---|---|---|---|
Subareas
|
Post-Development Design Storm
|
Pre-Development Design Storm
| ||
Runoff Control Districts
| ||||
A
|
1-4
|
2-year
|
1-year
| |
16
|
10-year
|
10-year
| ||
28-39
|
50-year
|
50-year
| ||
58-59
| ||||
B
|
5-15
| |||
17-27
|
2-year
|
1-year
| ||
40-55
|
10-year
|
5-year
| ||
60-65
|
50-year
|
25-year
| ||
70-75
| ||||
C
|
79-81
| |||
56-57
|
2-year
|
1-year
| ||
66-69
|
10-year
|
10-year
| ||
76-78
|
50-year
|
50-year
| ||
82-92
|
Table 307-1: Acceptable Stormwater Management
Computation Methodologies
| |||
---|---|---|---|
Method
|
Method Developer
|
Applicability
| |
TR-20 (or commercial package based on TR-20)
|
USDA NRCS
|
Where use of full hydrologic computer model
is desirable or necessary.
| |
TR-55 (or commercial package based on TR-55)
|
USDA NRCS
|
For plans within limitations described in TR-55.
| |
HEC-1, HEC-HMS
|
US Army Corps of Engineers
|
Where use of full hydrologic computer model
is desirable or necessary.
| |
PSRM
|
Penn State University
|
Where use of full hydrologic computer model
is desirable or necessary.
| |
Rational Method
|
Emil Kuichling (1889)
|
For sites less than 10 acres, or as approved
by the Municipal Engineer.
| |
Other Methods
|
Varies
|
Other computations approved by Municipal Engineer.
|