B.
For all regulated activities, unless preparation of an SWM site plan is specifically exempted in § 155-12:
C.
SWM site plans approved by the Municipality, in accordance with § 155-20, shall be on site throughout the duration of the regulated activity.
D.
The Municipality may, after consultation with the DEP, 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.
E.
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 this chapter and to meet
all requirements under Title 25 of the Pennsylvania Code and the Clean
Streams Law. Various BMPs and their design standards are listed in
the Erosion and Sediment Pollution Control Program Manual (E&S
Manual)2, No. 363-2134-008 (March 2012),
as amended and updated.
G.
Impervious areas.
(1)
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.
(2)
For development taking place in stages, the entire development plan
must be used in determining conformance with this chapter.
(3)
Stormwater calculations. For redevelopment projects in which the
existing site is already controlled by a stormwater management facility,
the requirement to consider 20% of existing impervious area as meadow
is waived, provided the existing facility meets the water quality,
volume, and peak rate standards and criteria of this chapter.
H.
Stormwater flows onto adjacent property shall not be created, increased,
decreased, relocated, or otherwise altered without written notification
of the adjacent property owner(s). Such stormwater flows shall be
subject to the requirements of this chapter.
I.
All regulated activities shall include measures to:
(1)
Protect health, safety, and property;
(2)
Meet the water quality goals of this chapter by implementing measures
outlined in the Pennsylvania Stormwater Best Management Practices
Manual (BMP Manual)1 to:
(a)
Minimize disturbance to floodplains, wetlands, and wooded areas.
(b)
Maintain or extend riparian buffers.
(c)
Avoid erosive flow conditions in natural flow pathways.
(d)
Minimize thermal impacts to waters of this commonwealth.
(e)
Disconnect impervious surfaces by directing runoff to pervious
areas, wherever possible.
(3)
To the maximum extent practicable, incorporate the techniques for
low-impact development practices described in the BMP Manual1.
J.
The design of all facilities over karst and mined areas shall include
an evaluation of measures to minimize adverse effects.
K.
Infiltration BMPs should be spread out, made as shallow as practicable,
and located to maximize use of natural on-site infiltration features
while still meeting the other requirements of this chapter.
L.
Storage facilities, to the greatest extent possible and at the discretion
of the Municipal Engineer, shall completely drain both the volume
control and rate control capacities over a period of time not less
than 24 hours and not more than 72 hours from the end of the design
storm.
M.
Storage facilities shall incorporate features to maximize the length
of the flow path and increase the travel time through the facility.
N.
The design storm volumes 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, Version 3.0, United States
Department of Commerce, National Oceanic and Atmospheric Administration
(NOAA), National Weather Service, Hydrometeorological Design Studies
Center, Silver Spring, Maryland. NOAA's Atlas 14 can be accessed
at: http://hdsc.nws.noaa.gov/hdsc/pfds/.5
O.
For all regulated activities, SWM BMPs shall be designed, implemented,
operated, and maintained to meet the purposes and requirements of
this chapter and to meet all requirements under Title 25 of the Pennsylvania
Code, the Clean Streams Law, and the Storm Water Management Act.
P.
Various BMPs and their design standards are listed in the BMP Manual1.
A.
Regulated activities that create impervious areas or earth disturbance
shall adhere to Table III.1 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.1).
|
Table III.1
| |||||
|---|---|---|---|---|---|
|
Stormwater Management Requirements and Exemptions
| |||||
|
Proposed Impervious Area
(square feet)
|
Proposed Total Earth Disturbance
(square feet)
|
Chapter Exemptions
|
Stormwater Management Requirements
|
What is Required to Submit to Municipality?*
| |
|
< 1,000
|
< 5,000
|
Ensure § 155-11, General requirements, is met
|
N/A
| ||
|
1,000 to 5,000
|
5,000 to 10,000
|
Disconnected impervious area (DIA) as in Appendix C.12
|
Appendix C.1 worksheet and sketch (or equivalent)2
| ||
|
OR
|
OR
| ||||
|
Capture and control first 1 inch of runoff over proposed impervious
areas as in Appendix E2
|
Appendix E worksheet and sketch (or equivalent)2
| ||||
|
5,000 to 10,000
|
10,000 to 20,000
|
Capture and permanently remove the first 2 inches of runoff over proposed impervious areas as in § 155-13B of this chapter
|
Appendix D worksheet and sketch (or equivalent)2
| ||
|
>10,000
|
>20,000
|
None
|
All requirements of this chapter
|
SWM site plan
| |
|
NOTES:
| ||
|---|---|---|
|
*
|
In addition to the stormwater management permit application
provided in Appendix B.2
| |
B.
Agricultural activity is 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.
C.
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.
The low-impact development practices provided in the BMP Manual1 shall be utilized for all regulated activities to
the maximum extent practicable. 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 that require submission
of a formal SWM site plan, both the Design Storm Method and the Simplified
Method shall be calculated; the larger control volume based on the
two calculations shall be controlled. Subsection C below provides
requirements for mined, karst, or other geologically limiting areas
where infiltration shall not occur.
A.
The Design Storm Method (CG-1 in the BMP Manual1) 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.
B.
When Design Storm Method CG-1 guidelines are not used, the Simplified
Method (CG-2 in the BMP Manual1) has been
modified to accommodate two inches of permanently removed runoff volume.
This method (provided below) is independent of site conditions and
should be used if the Design Storm Method is not followed. For new
impervious surfaces:
(1)
The first two inches 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.
(2)
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.
(3)
Facilities, to the greatest extent possible and subject to the Municipal
Engineer's discretion, shall be designed to drain the permanently
removed runoff volume in a period no less than 24 hours and no greater
than 72 hours.
(4)
Runoff volume in excess of two inches shall be safely conveyed to
existing stormwater collection systems or streams, in the direction
of the existing drainagecourse.
C.
Before infiltration is proposed on a site, site conditions shall
be evaluated by a qualified design professional through subsurface
investigation and testing to determine if site conditions are suitable
to support proposed infiltration facilities to manage runoff. If it
is determined that infiltration is not feasible due to physical constraints
of the site, or will adversely impact the environment as demonstrated
by the presence of acid mine drainage, sinkhole formation, or other
serious environmental issues, then the above volume controls must
be achieved through surface BMP mitigation. Reference the BMP Manual1 for alternative mitigation measures that do not require
infiltration.
A.
Areas not covered by a Stormwater Management District Map contained
in Appendix F.1.[1] Post-development discharge rates shall not exceed the
predevelopment discharge rates for the one-year through one-hundred-year,
twenty-four-hour 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-year through 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.
[1]
Editor's Note: The appendixes are on file in the municipal
offices.
B.
Areas covered by a Stormwater Management District Map contained in
Appendix F.1.[2] For the one-year through one-hundred-year storms, the
post-development peak discharge rates will follow the applicable approved
Stormwater Management District Maps. For any areas not shown on the
Stormwater Management District Maps, the post-development discharge
rates shall not exceed the predevelopment discharge rates.
[2]
Editor's Note: The appendixes are on file in the municipal
offices.
