A.
No regulated activities shall commence until the municipality approves
a plan, which demonstrates compliance with the requirements of this
chapter.
B.
Plans approved by the municipality shall be on site throughout the
duration of the regulated activity.
C.
The municipality may, after consultation with 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.
D.
For all regulated activities, implementation of water quality controls
are required.
E.
For all regulated activities equal to or greater than 1,000 square
feet in area, implementation of peak rate controls and preparation
of a SWM site plan are required.
F.
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)
For projects that add impervious area to a parcel, the total impervious
area on the parcel is subject to the requirements of this chapter.
G.
Discharges onto adjacent property shall not be created, increased,
decreased, or relocated, or otherwise altered, without permission
of the adjacent property owner(s). Such discharges shall be subject
to the requirements of this chapter.
H.
All regulated activities shall include such measures as necessary
to:
(1)
Protect health, safety, and property;
(3)
Meet the water quality goals of this chapter by implementing measures
to:
(a)
Minimize disturbance to floodplains, wetlands, natural slopes
over 15%, and existing native vegetation.
(b)
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.
(c)
Establish and maintain nonerosive flow conditions in natural
flow pathways.
(d)
Minimize soil disturbance and soil compaction. Cover disturbed
areas with topsoil having a minimum depth of four inches. Use tracked
equipment for grading when feasible.
(e)
Disconnect impervious surfaces by directing runoff to pervious
areas.
(4)
Incorporate the techniques described in Appendix A, Low-Impact Development Practices,[2] whenever practical.
[2]
Editor's Note: Appendix A is included at the end of this chapter.
I.
The design of all facilities over karst shall include an evaluation
of measures to minimize adverse effects.
J.
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, U.S. 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/.
A.
Regulated activities that create less than 1,000 square feet of new
impervious area and that meet the area of influence (A) requirements
shown in Table 1A are exempt from the peak rate control and the SWM
site plan preparation requirement of this chapter.
|
TABLE 1A: SWM Exemptions From
Peak Rate Controls and SWM Site Plan Preparation
for
Area of Influence (A) Less Than Three Acres
| ||
|---|---|---|
|
Area of Influence (A)
(acres)
|
Total Impervious Area (a) Exempt From Peak Rate Controls
and from SWM site plan Preparation
(square feet)
| |
|
<0.125
|
1,000
| |
|
0.2
|
1,400
| |
|
0.3
|
1,900
| |
|
0.4
|
2,300
| |
|
0.5
|
2,700
| |
|
0.6
|
3,100
| |
|
0.7
|
3,500
| |
|
0.8
|
3,900
| |
|
0.9
|
4,200
| |
|
1.0
|
4,600
| |
|
1.1
|
4,900
| |
|
1.2
|
5,200
| |
|
1.3
|
5,500
| |
|
1.4
|
5,900
| |
|
1.5
|
6,200
| |
|
1.6
|
6,500
| |
|
1.7
|
6,800
| |
|
1.8
|
7,100
| |
|
1.9
|
7,300
| |
|
2.0
|
7,600
| |
|
2.1
|
7,900
| |
|
2.2
|
8,200
| |
|
2.3
|
8,400
| |
|
2.4
|
8,700
| |
|
2.5
|
9,000
| |
|
2.6
|
9,200
| |
|
2.7
|
9,500
| |
|
2.8
|
9,800
| |
|
2.9
|
10,000
| |
|
NOTE:
| |
|---|---|
|
The area of influence (A), in acres, and the total impervious area (a), in square feet, are calculated using the guidelines provided in Appendix D.[1]
|
[1]
Editor's Note: Appendix D is included at the end of this chapter.
B.
Regulated activities that create less than 1,000 square feet of new
impervious area and that meet the area of influence (A) requirements
shown in Table 1B are exempt from the rate control requirements of
this chapter.
|
TABLE 1B: SWM Exemptions From Peak Rate Controls Only
for
Area of Influence (A) of Three Acres or Greater
| ||
|---|---|---|
|
Area of Influence (A)
(acres)
|
Total Impervious Area (a) Exempt from Peak Rate Controls
Only
(square feet)
| |
|
3
|
10,300
| |
|
3.1
|
10,500
| |
|
3.2
|
10,800
| |
|
3.3
|
11,000
| |
|
3.4
|
11,300
| |
|
3.5
|
11,500
| |
|
3.6
|
11,700
| |
|
3.7
|
12,000
| |
|
3.8
|
12,200
| |
|
3.9
|
12,500
| |
|
4
|
12,700
| |
|
4.1
|
12,900
| |
|
4.2
|
13,200
| |
|
4.3
|
13,400
| |
|
4.4
|
13,600
| |
|
4.5
|
13,800
| |
|
4.6
|
14,100
| |
|
4.7
|
14,300
| |
|
4.8
|
14,500
| |
|
4.9
|
14,700
| |
|
5
|
15,000
| |
|
>5
|
15,000
| |
|
NOTE:
| |
|---|---|
|
The area of influence (A), in acres, and the total impervious area (a), in square feet, are calculated using the guidelines provided in Appendix D.[2]
|
[2]
Editor's Note: Appendix D is included at the end of this chapter.
C.
Use the guidelines in Appendix D[3] to determine the area of influence (A) in acres, and the
total impervious area (a), in square feet, to determine if an exemption
is applicable for regulated activities less than 1,000 square feet.
[3]
Editor's Note: Appendix D is included at the end of this chapter.
D.
After the date of the chapter adoption, if a subdivision and land
development plan is submitted that addresses peak rate control and
includes a SWM site plan, then the impervious exemption is calculated
from the date of approval of that plan, based upon the impervious
area shown on the subdivision and land development plan.
E.
Agricultural plowing and tilling are exempt from the rate control
and SWM site plan preparation requirements of this chapter, provided
that the activities are performed according to the requirements of
25 Pa. Code Chapter 102.
A.
Low-impact development practices (Appendix A)[1] are encouraged for all regulated activities.
[1]
Editor's Note: Appendix A is included at the end of this chapter.
B.
(1)
The Simplified Method is independent of site conditions.
(a)
Retention and detention facilities shall be sized to capture
the first two inches of runoff from all impervious surfaces.
(b)
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.
(c)
For projects that meet the exemption criteria in Table 1A of § 177-9, the subsequent one inch of runoff shall be detained. This is the extended detention volume (EDV).
(d)
For projects that do not meet the exemption criteria in Table 1A of § 177-9, the one-year, twenty-four-hour runoff volume shall be detained.
(e)
Infiltration of the first 1/2 inch of the PRV is encouraged.
This portion of the PRV is the groundwater recharge volume (GRV).
(f)
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.
(g)
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.
(h)
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.
(2)
The Design Storm Method requires detailed modeling based on site
conditions.
(a)
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.
(b)
Do not increase peak rate of runoff for one-, two-, ten-, twenty-five-,
one-hundred-year storms (at minimum), pre-development to post-development;
as necessary, provide additional peak rate control as required by
Act 167 planning.
(c)
Existing (pre-development) nonforested pervious areas must be
considered meadow or its equivalent.
(d)
Twenty percent of existing impervious area, when present, shall
be considered meadow in the model for existing conditions.
(3)
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 hours and not more than 96 hours from the start of
the design storm.
A.
Areas not covered by a Release Rate Map from an approved Act 167
stormwater management plan. Post-development discharge rates shall
not exceed the pre-development 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 pre-development 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.
B.
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 pre-development discharge rates.
