At least the first one-inch of runoff from new or replacement
impervious surfaces shall be infiltrated.
| |
Rev = one (inch)* impervious area (square
feet) + 12 (inches) = cubic feet (cf)
| |
[An asterisk (*) in equations denotes multiplication.]
|
Rev = I * impervious area (square feet)
+ 12 (inches) = cubic feet (cf)
| ||||
An asterisk (*) in equations denotes multiplication.
| ||||
Where:
| ||||
I
|
=
|
The maximum equivalent infiltration amount (inches) that the
site can physically accept or 0.50 inch, whichever is greater.
|
Table 257-17.1
Peak Rate Control Standards in the Crum Creek Watershed
| |||
---|---|---|---|
District
|
Proposed Condition Design Storm
(reduce to)
|
Existing Condition Design Storm
| |
A
|
2-year
|
1-year
| |
5-year
|
5-year
| ||
10-year
|
10-year
| ||
25-year
|
25-year
| ||
50-year
|
50-year
| ||
100-year
|
100-year
| ||
B
|
2-year
|
1-year
| |
5-year
|
2-year
| ||
10-year
|
5-year
| ||
25-year
|
10-year
| ||
50-year
|
25-year
| ||
100-year
|
100-year
|
Table 257-17.2
Peak Rate Control Standards by Stormwater Management District
in the Darby-Cobbs Creek Watershed
| |||
---|---|---|---|
District
|
Proposed Condition Design Storm
|
Existing Condition Design Storm
| |
A
|
2-year
|
1-year
| |
5-year
|
5-year
| ||
10-year
|
10-year
| ||
25-year
|
25-year
| ||
100-year
|
100-year
| ||
B-1
|
2-year
|
1-year
| |
10-year
|
5-year
| ||
25-year
|
10-year
| ||
50-year
|
25-year
| ||
100-year
|
100-year
| ||
B-2
|
2-year
|
1-year
| |
5-year
|
2-year
| ||
25-year
|
5-year
| ||
50-year
|
10-year
| ||
100-year
|
100-year
| ||
C
|
Conditional Direct Discharge District
|
Table 257-20.1
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.
| |
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
and/or Municipal Engineer.
| |
Other methods
|
Varies
|
Other computation methodologies approved by the municipality
and/or Municipal Engineer.
|