[Ord. 3-2016, 10/13/2016]
1.
No regulated activities shall commence until the municipality approves
a plan which demonstrates compliance with the requirements of this
chapter.
2.
Plans approved by the municipality shall be on site throughout the
duration of the regulated activity.
3.
The municipality may, after consultation with the DEP, approve methods
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.
4.
For all regulated activities, implementations of water quality controls
are required.
5.
For all regulated activities equal to or greater than 1,000 square
feet in area, implementation of peak rate controls and preparation
of an SWM site plan are required.
6.
Impervious Areas:
A.
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.
B.
For development taking place in stages, the entire development plan
must be used in determining conformance with this chapter.
C.
For projects that add impervious area to a parcel, the total impervious
area on the parcel is subject to the requirements of this chapter.
7.
Discharges onto adjacent property shall not be created, increased,
decreased, relocated, or otherwise altered without permission of the
adjacent property owner(s). Such discharges shall be subject to the
requirements of this chapter.
8.
All regulated activities shall include such measures as necessary
to:
A.
Protect health, safety, and property;
B.
Meet state water quality requirements as defined in Part 2;
C.
Meet the water quality goals of this chapter by implementing measures
to:
(1)
Minimize disturbance to floodplains, wetlands, natural slopes
over 15%, and existing native vegetation.
(2)
Preserve and maintain trees and woodlands. Maintain or extend
riparian buffers and protect existing forested buffer. Provide trees
and woodlands adjacent to impervious areas whenever feasible.
(3)
Establish and maintain nonerosive flow conditions in natural
flow pathways.
(4)
Minimize soil disturbance and soil compaction. Cover disturbed
areas with topsoil having a minimum dept of four inches. Use tracked
equipment for grading when feasible.
(5)
Disconnect impervious surfaces by directing runoff to pervious
areas.
9.
The design of all facilities over karst shall include an evaluation
of measures to minimize adverse effects.
10.
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, United States Department
of Commerce, National Oceanic and Atmospheric Administration, National
Weather Service, Hydrometeorological Design Studies Center, Silver
Spring, Maryland, 20910. NOAA's Atlas 14 can be accessed at Internet
address: http://hdsc.nws.noaa.gov/hdsc/pfds/.
[Ord. 3-2016, 10/13/2016]
2.
A.
The Simplified Method is independent of site conditions.
(1)
Retention and detention facilities shall be sized to capture
the first two inches of runoff from all impervious surfaces.
(2)
The first one inch of runoff shall be permanently removed and
shall not be released into the surface waters of this commonwealth.
This is the permanently removed volume (PRV). Removal options include
reuse, evaporation, transpiration, and infiltration.
(3)
For projects that meet the exemption criteria in § 17-402, the subsequent one inch of runoff shall be detained. This is the extended detention volume (EDV).
(4)
For projects that do not meet the exemption criteria in § 17-402, the one-year, twenty-four-hour runoff volume shall be detained.
(5)
Infiltration of the first 1/2 inch of the PRV is encouraged.
This portion of the PRV is the groundwater recharge volume (GRV).
(6)
The permanently removed volume (PRV) requirement for land areas
with existing cover consisting of meadow, brush, wood-grass combination,
or woods proposed for conversion to any other nonequivalent type of
pervious cover shall be 1/4 inch of runoff.
(7)
Retention and detention facilities should be designed to drain
both the PRV and EDV completely within 48 hours to 96 hours from the
start of the storm.
(8)
Retention facilities should be designed to accommodate infiltration
of the PRV. Infiltration areas should be spread out and located in
the sections of the site that are most suitable for infiltration.
B.
The Design Storm 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
rainfall.
(2)
Do not increase peak rate of runoff for one-, two-, ten-, twenty-five-,
and one-hundred-year storms (at minimum), predevelopment to post-development;
as necessary, provide additional peak rate control as required by
Act 167 planning.
(3)
Existing (predevelopment) nonforested pervious areas must be
considered meadow or its equivalent.
(4)
Twenty percent of existing impervious area, when present, shall
be considered meadow in the model for existing conditions.
C.
In all cases, retention and detention facilities should be designed
to completely drain water quality volumes (in the case of the Simplified
Method, this includes both the PRV and EDV) over a period of time
not less than 48 and not more than 96 hours from the start of the
design storm.
[Ord. 3-2016, 10/13/2016]
1.
Areas not covered by a release rate map from an approved Act 167
Stormwater Management Plan:
Post-development discharge rates shall not exceed the predevelopment
discharge rates for the 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 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.
2.
Areas covered by a release rate map from an approved Act 167 Stormwater
Management Plan:
For the two-, five-, ten-, twenty-five-, fifty-, and one-hundred-year
storms, the post-development discharge rates will follow the release
rate maps in this chapter. For any areas not shown on the release
rate maps, the post-development discharge rates shall not exceed the
predevelopment discharge rates.
