[Amended 2-28-2023 by Ord. No. 4-2023]
A. Regulated activities that create new impervious areas or earth disturbance
shall adhere to Table III to meet the requirements of this chapter.
The larger of the two areas determines the applicable requirements
of this chapter (i.e., if only 500 square feet of impervious area
is proposed, but 15,000 square feet of earth disturbance, the requirements
follow row 3 of Table III).
B. Agricultural activity is exempt from the stormwater management (SWM)
site plan preparation requirements of this chapter provided the activities
are performed according to the requirements of 25 Pa. Code Section
102.
C. Forest management and timber operations are exempt from the SWM site
plan preparation requirements of this chapter provided the activities
are performed according to the requirements of 25 Pa. Code Section
102.
D. Exemptions from any provisions of this chapter shall not relieve the applicant from the requirements in §
260-12D through
K and
N.
E. The municipality may deny or revoke any exemption pursuant to this
section at any time for any project that the municipality believes
may pose a threat to public health and safety or the environment.
Table III Stormwater Management Requirements and Exemptions
|
---|
Proposed Impervious Area
(square feet)
|
Proposed Total Earth Disturbance
(square feet)
|
Ordinance Exemptions
|
Stormwater Management Requirements
|
What Is Required to Submit to Municipality?
(in addition to stormwater application)
|
---|
<1,000
|
<5,000
|
|
|
N/A
|
1,000 to 5,000
|
5,000 to 10,000
|
|
Disconnected impervious area (DIA) as in Appendix C.1
|
Appendix C.1 Worksheet and Sketch (or equivalent)
|
or
|
or
|
Capture and control first 1 inch of runoff over proposed impervious
areas as in Appendix E
|
Appendix E worksheet and sketch (or equivalent)
|
5,000 to 10,000
|
10,000 to 20,000
|
|
Capture and permanently remove the two inches of runoff over proposed impervious areas as in § 260-14B of this chapter
|
Appendix D worksheet and sketch (or equivalent)
|
>10,000
|
>20,000
|
None
|
All requirements of this chapter
|
All requirements of this chapter
|
The green infrastructure and low-impact development practices
provided in the BMP Manual shall be utilized for all regulated activities
wherever possible. Water volume controls shall be implemented using
the Design Storm Method in Subsection A or the Simplified Method in
Subsection B below. For regulated activity areas equal to or less
than one acre that do not require hydrologic routing to design the
stormwater facilities, this chapter establishes no preference for
either methodology; therefore, the applicant may select either methodology
on the basis of economic considerations, the intrinsic limitations
on applicability of the analytical procedures associated with each
methodology and other factors.
A. The Design Storm Method (CG-1 in the BMP Manual) is applicable to
any size of regulated activity. This method requires detailed modeling
based on site conditions.
(1) Do not increase the post-development total runoff volume for all
storms equal to or less than the two-year twenty-four-hour duration
precipitation.
(2) For modeling purposes:
(a)
Existing (predevelopment) nonforested pervious areas must be
considered meadow in good condition.
(b)
Twenty percent of existing impervious area, when present, shall
be considered meadow in good condition in the model for existing conditions.
B. The Simplified Method (CG-2 in the BMP Manual) provided below is independent of site conditions and should
be used if the Design Storm Method is not followed. This method is
not applicable to regulated activities greater than one acre or for
projects that require design of stormwater storage facilities. For
new impervious surfaces:
(1) Stormwater facilities shall capture at least the first two inches
of runoff from all new impervious surfaces.
(2) At least the first one inch of runoff from new impervious surfaces
shall be permanently removed from the runoff flow, i.e., it shall
not be released into the surface waters of this commonwealth. Removal
options include reuse, evaporation, transpiration, and infiltration.
(3) Wherever possible, infiltration facilities should be designed to
accommodate infiltration of the entire permanently removed runoff;
however, in all cases, at least the first 0.5 inch of the permanently
removed runoff should be infiltrated.
(4) This method is exempt from the requirements of §
260-15, Rate controls.