Table 1
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---|---|
TSS Reduction Standards
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Development Type
|
TSS Reduction
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New Development
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80%
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In-Fill Development
|
80%
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Redevelopment
|
40% of load from parking areas and roads
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Table 2
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---|---|---|---|---|
Maximum Pre-Development Runoff Curve Numbers
| ||||
Runoff Curve Number
|
Hydrologic Soil Group
| |||
A
|
B
|
C
|
D
| |
Woodland
|
30
|
55
|
70
|
77
|
Grassland
|
39
|
61
|
71
|
78
|
Cropland
|
55
|
69
|
78
|
83
|
Note to Users: The intent of the peak discharge
standard is to minimize stream bank erosion, under bank-full conditions.
For water quantity concerns, the post-development peak flow rate for
the ten-, twenty-five-, fifty- and 100-year twenty-four hour storm
events should also be controlled either at or below pre-development
discharge rates. This has not been addressed in this model ordinance
but may need to be included in the local ordinance to address local
flood control issues.
|
Note to Users: Runoff from the employee
and guest parking and rooftop areas of a tier 2 facility may be infiltrated
but runoff from the parking area may require pretreatment.
|
Table 3
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---|---|---|
Separation Distances and Soil Characteristics
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Source Area
|
Separation Distance
|
Soil Characteristics
|
Industrial, Commercial, Institutional Parking Lots and Roads
|
5 feet or more
|
Filtering Layer
|
Residential Arterial Roads
|
5 feet or more
|
Filtering Layer
|
Roofs Draining to Subsurface Infiltration Practices
|
1 foot or more
|
Native or Engineered Soil with Particles Finer than Coarse Sand
|
Roofs Draining to Surface Infiltration Practices
|
Not Applicable
|
Not Applicable
|
All Other Impervious Source Areas
|
3 feet or more
|
Filtering Layer
|
Note to Users: It is recommended that seeding
of non-invasive vegetative cover be used in the protective areas.
Some invasive plants that should not be used are listed in ch. NR
40, Wis. Adm. Code. Flood and drought-tolerant vegetation that can
provide long-term bank stability because of an extensive root system
is preferable. Vegetative cover may be measured using the line transect
method described in the University of Wisconsin extension publication
number A3533, titled "Estimating Residue Using the Line Transect Method".
|
Note to Users: A vegetated protective area
to filter runoff pollutants from post-construction sites described
in par. (v) is not necessary since the runoff at that location is
treated prior to entering the surface water. Other practices necessary
to meet the requirements of this section, such as a swale or pond,
will need to be designed and implemented to reduce runoff pollutants
prior to runoff entering a surface water of the state.
|
Note to Users: A combination of the following
BMPs may be used: oil and grease separators, canopies, petroleum spill
cleanup materials, or any other structural or nonstructural method
of preventing or treating petroleum in runoff.
|
Note to Users: It is preferred that tall
and dense vegetation be maintained within the swale due to its greater
effectiveness at enhancing runoff pollutant removal.
|