A.
For all regulated activities, unless preparation of a SWM site plan is specifically exempted in § 249-11:
B.
SWM site plans approved by the Township, in accordance with § 249-20, shall be on site throughout the duration of the regulated activity.
C.
The Township, after consultation with DEP, may approve measures for
meeting the state water quality requirements other than those in this
chapter, provided that they meet the minimum requirements of, and
do not conflict with, state law including but not limited to the Clean
Streams Law.[1]
[1]
Editor's Note: See 35 P.S. § 691.1 et seq.
D.
For all regulated earth disturbance activities, erosion and sediment
control BMPs shall be designed, implemented, operated, and maintained
during the regulated earth disturbance activities (e.g., during construction)
to meet the purposes and requirements of an erosion and sedimentation
control plan that has been deemed adequate by the Cumberland County
Conservation District and/or Pennsylvania Department of Environmental
Protection.
F.
For all new development projects, the measurement of impervious areas
shall include all of the impervious areas in the total proposed development
even if development is to take place in stages. Similarly, for new
development projects taking place in stages, the entire proposed new
development plan must be used in determining conformance with this
chapter.
G.
Stormwater flows and/or direct discharges shall not be created, increased,
decreased, relocated, or otherwise altered in a manner which would
affect any adjacent, contiguous or nearby properties without demonstrating
that the owners of the such affected properties have been made aware
of the flow/direct discharge which is intended to enter upon their
property.
H.
The design of all facilities over Karst topography shall include
an evaluation of measures to minimize adverse effects in accordance
with the procedures outlined in Section 7.4 (Special Management Areas
- Karst Areas) of the most current version of the SWM Manual.[2]
I.
Storage facilities should completely drain both the volume control
and rate control capacities within 72 hours from the end of the design
storm subject to site conditions.
J.
The design storm precipitation depth estimates to be used in the
analysis of peak rates of discharge should be obtained from the Precipitation-Frequency
Atlas of the United States, Atlas 14, Volume 2, U.S. Department of
Commerce, National Oceanic and Atmospheric Administration (NOAA),
National Weather Service, Hydrometeorological Design Studies Center,
Silver Spring, Maryland, 20910. NOAA's Atlas 14[3] can be accessed at Internet address: http://hdsc.nws.noaa.gov/hdsc/pfds/.
K.
For all regulated activities, SWM BMPs shall be designed, implemented,
operated, and maintained to meet the purposes and requirements of
this chapter. In addition, the BMPs shall meet all requirements under
Title 25 of the Pennsylvania Code, the Clean Streams Law,[4] and the Storm Water Management Act,[5] as required and enforced by the governing agencies.
A.
Regulated activities resulting in less than or equal to 1,000 square feet of new impervious surface are exempt from Article IV, SWM Site Plan Preparation Requirements, including §§ 249-12 and 249-13 of this chapter. Regulated activities greater than 1,000 square feet and less than or equal to 5,000 square feet of new impervious area may be exempt from the SWM site plan preparation requirements, including §§ 249-12 and 249-13, of this chapter when justification is provided with the application that stormwater impact is minimal. [Note: The Township has, at its discretion, the ability to deny exemption from any requirements of this chapter. Exemption from any requirements of this chapter does not convey exemption from any requirements of any other applicable local codes or ordinances (i.e., local building permit requirements).]
B.
Regulated activities that create new disconnected impervious areas
greater than 1,000 square feet and less than or equal to 5,000 square
feet that are proven to meet the seventy-five-foot minimum pervious
flow path requirement outlined in Appendix A[1] are exempt from the SWM site plan preparation requirements including §§ 249-12 and 249-13 of this chapter. [Note: The Township has, at its discretion, the ability to deny exemption from any requirements of this chapter. Exemption from any requirements of this chapter does not convey exemption from any requirements of any other applicable local codes or ordinances (i.e., local building permit requirements).]
[1]
Editor's Note: Appendix A is included as an attachment to this chapter.
C.
Regulated activities meeting the following parcel size and square
footage requirements are exempt from the peak rate control requirements,
but not the volume control or SWM site plan preparation requirements
of this chapter. These criteria shall apply to the total proposed
development even if development is to take place in phases. The date
of the municipal ordinance adoption shall be the starting point from
which to consider tracts as "parent tracts" in which future subdivisions
and respective impervious area computations shall be cumulatively
considered. [Note: The Township has, at its discretion, the ability
to deny exemption from any requirements of this chapter. Exemption
from any requirements of this chapter does not convey exemption from
any requirements of any other applicable local codes or ordinances
(i.e., local building permit requirements).]
|
New Impervious Area Exemption Criteria for Peak Rate Control
| |||
|---|---|---|---|
|
Total Parcel Size
(acres)
|
Total Parcel Size
(square feet)
|
New Impervious Area Exemption
(square feet)
| |
|
<0.25
|
<10,890
|
1,500
| |
|
0.25 to 0.5
|
10,890 to 21,780
|
2,500
| |
|
>0.5
|
>21,780
|
5,000
| |
E.
Forest management and timber operations are exempt from the rate
control and SWM site plan preparation requirements of this chapter,
provided the activities are performed according to the requirements
of 25 Pa. Code Chapter 102.
Water volume controls shall be implemented using the Design Storm Method in Subsection A or the Simplified Method in Subsection B below for all regulated activities not otherwise exempted by § 249-11. For regulated activity areas equal 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 (see Section 8.7 of the most current version
of the SWM Manual[1]) 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 or its equivalent.
(b)
Twenty percent of existing impervious area, when present, shall
be considered meadow in the model for existing conditions.
[or]
(c)
Calculate existing (predevelopment) stormwater runoff and infiltration
volumes based on existing site conditions, as verified through design
phase soil infiltration testing.
B.
The Simplified Method (see Section 8.7 of the most current version
of the SWM Manual)[2] 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 detention or rate control
facilities. For new impervious surfaces:
(1)
Stormwater facilities shall be sized to 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)
Infiltration facilities should be designed to accommodate infiltration
of the entire permanently removed runoff; however, in all cases, at
least the first 1/2 inch of the permanently removed runoff should
be infiltrated.
(4)
The second one inch of runoff from new impervious surfaces should
be detained using structural and nonstructural BMPs (as outlined in
the most current version of the SWM Manual) and released at a controlled
rate.
A.
Areas not covered by a Release Rate Map from an approved Act 167
Stormwater Management Plan:
(1)
Post-development discharge rates shall not exceed the predevelopment
discharge rates for the one-, two-, five-, ten-, twenty-five-, fifty-,
and one-hundred-year storms. If it is shown that the peak rates of
discharge indicated by the post-development analysis are less than
or equal to the peak rates of discharge indicated by the predevelopment
analysis for one-, two-, five-, ten-, twenty-five-, fifty-, and one-hundred-year,
twenty-four-hour storms, then the requirements of this section have
been met. Otherwise, the applicant shall provide additional controls
as necessary to satisfy the peak rate of discharge requirement.
B.
Areas covered by a Release Rate Map from an approved Act 167 Stormwater
Management Plan (see Appendix B):[2]
(1)
For the one-, two-, five-, ten-, twenty-five-, fifty-, and one-hundred-year
storms, the post-development peak discharge rates will follow the
applicable approved release rate maps (see Appendix B). For any areas
not shown on the release rate maps, the post-development discharge
rates shall not exceed the predevelopment discharge rates.
[2]
Editor's Note: Appendix B is included as an attachment to this chapter.
[1]
Note: See Section 8.3 of the most current version of the SWM
Manual
The SWM site plan shall also satisfy the stormwater management and design criteria in Chapter 260, Subdivision and Land Development, for projects meeting the definition of "land development" as defined in that chapter.
