A.
For all regulated activities, unless preparation of an SWM site plan is specifically exempted in § 210-13:
B.
SWM site plans approved by Richland Township, in accordance with § 210-21, shall be on site throughout the duration of the regulated activity.
C.
The municipality may, after consultation with 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.[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 this chapter and to meet
all requirements under the Pennsylvania Code Title 25 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] Commonwealth of Pennsylvania, Department of Environmental
Protection, No. 363-2134-008, as amended and updated.
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.
Stormwater flows onto adjacent property shall not be created, increased,
decreased, relocated, or otherwise altered without written permission
of the adjacent property owner(s). Such stormwater flows 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 8%, 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 non-erosive flow conditions in natural
flow pathways.
(d)
Minimize soil disturbance and soil compaction. Over disturbed
areas, replace topsoil to a minimum depth equal to the original depth
or four inches, whichever is greater. Use tracked equipment for grading
when feasible.
(e)
Minimize thermal impacts to water of this commonwealth.
(f)
Disconnect impervious surfaces by directing runoff to pervious
areas, wherever possible.
I.
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.
J.
Normally dry, open top, storage facilities should completely drain
both the volume control and rate control capacities over a period
of time not less than 24 and not more than 72 hours from the end of
the design storm.
K.
L.
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 (NOAA), National Weather
Service, Hydrometeorological Design Studies Center, Silver Spring,
Maryland, 20910. NOAA's Atlas 14[6] can be accessed at internet address: http://hdsc.nws.noaa.gov/hdsc/pfds/.
N.
The applicant may meet the rate controls criteria in § 210-15 through off-site stormwater management measures as long as the proposed measures are in the same subwatershed. Off-site stormwater control measures may only be sought if it is shown that on-site stormwater control measures cannot be physically accomplished. This does not relieve the applicant from meeting the volume controls criteria in § 210-14 on-site.
O.
Where a development is traversed by watercourses, drainage easements
shall be provided conforming to the line of such watercourses. The
terms of the easement shall conform to the stream buffer requirements.
If a perennial or intermittent stream passes through the site, the
applicant shall create a stream buffer extending a minimum of 50 feet
to either side of the top-of-bank of the channel. The buffer area
shall be maintained with and encouraged to use appropriate native
vegetation (Reference to Appendix H of Pennsylvania Handbook of Best
Management Practices for Developing Area for plant lists). If the
applicable rear or side yard setback is less than 50 feet, the buffer
width may be reduced to 25% of the setback to a minimum of 10 feet.
If an existing buffer is legally prescribed (i.e., deed, covenant,
easement, etc.) and it exceeds the requirements of this chapter, the
existing buffer shall be maintained. This does not include lakes or
wetlands.
P.
Roof drains should not be connected to streets, sanitary or storm
sewers or roadside ditches to promote overland flow and infiltration/percolation
of stormwater where it is advantageous to do so. When it is more advantageous
to connect directly to streets or storm sewers, then it shall be permitted
on a case by case basis by Richland Township.
Q.
No regulated earth disturbance activities within Richland Township
shall commence until the requirements of the Ordinance are met.
R.
Evidence of any necessary permit(s) for regulated activities or regulated
earth disturbance from DEP, Cambria County Conservation District and
PA DOT must be provided.
S.
Water shall not be stored on a roof. Water stored on parking areas
and drive areas shall not exceed five inches in depth as measured
from the basin bottom to the emergency spillway crest.
T.
Storage must be open and accessible for visual inspection. Where
underground detention is provide, manhole/inlet access must be provided
to allow visual inspection.
U.
Provide a four-foot-height fence around surface detention basins
where two feet or more of water depth is stored measured from the
pond bottom to the crest of the emergency spillway.
V.
Where a detention basin is to be turned over to Richland Township
the following apply:
(1)
Property shall be granted to Richland Township in fee simple;
(2)
Access shall be granted to Richland Township in fee simple;
(3)
Access shall be a twelve-foot-wide gravel all weather roadway that
is seeded with lawn vegetation on a twenty-foot-wide access area;
(4)
Provide a six-foot-height vinyl clad chain link fence with twelve-foot-wide
access gate aligned with gravel access roadway;
(5)
Basin slopes shall have gradual slopes that are machine mowable;
(6)
Basin shall have access ramp for mobile equipment that aligns with
twelve-foot-wide access gate;
(7)
Developer shall provide a maintenance fee as established by Richland
Township by resolution to assist with future maintenance costs.
A.
Regulated activities that create disconnected impervious areas smaller
than 650 square feet are exempt from all requirements in this chapter.
B.
Regulated activities that create disconnected impervious areas equal
to or greater than 650 square feet and less than 5,000 square feet
are exempt from the peak rate control and the SWM site plan preparation
requirements of this chapter, but should comply with the small project
requirements found in Appendix F of the ordinance.[1]
[1]
Editor's Note: Said appendix is included as an attachment to this chapter.
C.
Regulated activities that create disconnected impervious areas equal
to or greater than 5,000 square feet and less than 10,000 square feet
are exempt only from the peak rate control requirement of this chapter.
D.
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.
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.
F.
Additional exemption criteria:
(1)
Exemption responsibilities. An exemption shall not relieve the applicant
from implementing such measures as are necessary to protect public
health, safety, and property.
(2)
HQ and EV streams. An exemption shall not relieve the applicant from
meeting the special requirements for watersheds draining to identified
high quality (HQ) or exceptional value (EV) waters and source water
protection areas (SWPA) and requirements for non-structural project
design sequencing.
(3)
Drainage problems. If a drainage problem is documented or known to
exist downstream of or is expected from the proposed activity, then
the municipality may require the applicant to comply with the chapter.
(4)
Even though the developer is exempt, he is not relieved from complying
with other regulations.
H.
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.
B.
Water volume controls shall be implemented using the design storm method in Subsection B(1) or the simplified method in Subsection B(2) below. For regulated activities that create 10,000 square feet or less of impervious cover 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.
(1)
The design storm method (CG-1 in the SWM Manual[2]) is applicable to any size of regulated activity. This
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
precipitation.
(2)
The simplified method (CG-2 in the BMP Manual[3]) 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 10,000 square
feet or for projects that require design of stormwater storage facilities.
For new impervious surfaces:
(a)
Stormwater facilities shall capture at least the first two inches
of runoff from all new impervious surfaces.
(b)
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.
(c)
Wherever possible, 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.
The post-development peak discharge rates will follow the applicable
approved management district or release rate map for the one-, two-,
five-, ten-, twenty-five-, fifty-, and 100-year, twenty-four-hour
storm events. The approved stormwater management release district
maps for the Little Connemaugh River and the Stonycreek River watersheds
are found in Appendix D.[1] The stormwater management subarea for the Little Conemaugh
River watershed is found in Table 1. The stormwater management district
criteria for the Stonycreek River watershed is found in Table 2. For
any areas not shown on the release rate maps or management district
maps, the post-development discharge rates shall not exceed the predevelopment
discharge rates.
|
Table 1
Stormwater Management Districts in the Little Conemaugh River
Watershed
| |
|---|---|
|
Subarea
|
Subarea Release Rate Factor
|
|
B-32
|
1
|
|
B-33
|
0.7
|
|
B-34
|
0.7
|
|
C-6
|
1
|
|
C-9
|
1
|
|
C-10
|
1
|
|
Table 2
Stormwater Management Districts in the Stonycreek River Watershed
| |||
|---|---|---|---|
|
District
|
Proposed Condition Design Storm
|
(reduce to)
|
Existing Condition Design Storm
|
|
A
|
2-year
|
1-year
| |
|
5-year
|
5-year
| ||
|
10-year
|
10-year
| ||
|
25-year
|
25-year
| ||
|
50-year
|
50-year
| ||
|
100-year
|
100-year
| ||
|
B-1
|
5-year
|
2-year
| |
|
10-year
|
5-year
| ||
|
25-year
|
10-year
| ||
|
50-year
|
25-year
| ||
|
100-year
|
100-year
| ||
|
B-2
|
2-year
|
2-year
| |
|
25-year
|
10-year
| ||
|
50-year
|
25-year
| ||
|
100-year
|
100-year
| ||
A.
Off-site areas that drain through a proposed development site are
not subject to release rate criteria when determining allowable peak
runoff rates. However, on-site drainage facilities shall be designed
to safely convey off-site flows through the development site.
B.
Any stormwater management facility designed to store runoff and requiring a berm or earthen embankment shall be designed to provide a concrete lined emergency spillway to safely pass the 100-year post-development flow plus be provided with one foot of freeboard. Should any stormwater management facility require a dam safety permit under PADEP Chapter 105, design shall comply with the Chapter 105 requirements.
C.
Any facilities that constitute water obstructions (e.g., culverts, bridges, stream enclosures, outfalls), and any work involving wetlands shall conform to PADEP Chapter 105. Design shall provide one-foot freeboard measured below the lowest point along the top of the roadway.
D.
Drainage conveyance facilities (storm sewers and channels) not falling under PADEP Chapter 105 must be able to convey post-development runoff from a twenty-five-year design storm without surcharging the facilities.
E.
Adequate erosion protection shall be provided along all open channels,
and at all points of discharge.
F.
Calculation methodology. Stormwater runoff from all development sites
shall be calculated using either the rational method or a soil-cover-complex
methodology.
(1)
Any stormwater runoff calculations shall use generally accepted calculation
technique that is based on the NRCS soil cover complex method. Table
311-1 summarizes acceptable computation methods. It is assumed that
all methods will be selected by the design professional based on the
individual limitations and suitability of each method for a particular
site. Richland Township may allow the use of the rational method to
estimate peak discharges from drainage areas that contain less than
five acres. The soil complex method is required for drainage areas
greater than five acres.
|
Table 311-1
Acceptable Computation Methodologies For Stormwater Management
Plans
| ||
|---|---|---|
|
Method
|
Method Developed By
|
Applicability
|
|
TR-20 (or commercial computer package based on TR-20)
|
USDA NRCS
|
Applicable where use of full hydrology computer model is desirable
or necessary
|
|
TR-55 (or commercial computer package based on TR-55)
|
USDA NRCS
|
Applicable for land development plans within limitations described
in TR-55
|
|
HEC-1/HEC-HMS
|
US Army Corps of
|
Applicable where use of full hydrologic computer model is
|
|
PSRM
|
Penn State University
|
Applicable where use of a hydrologic computer model is
|
|
Rational method (or commercial computer package based on rational
method)
|
Emil Kuichling (1889)
|
For sites less than 200 acres, or as approved by the municipality
|
|
Other methods
|
Varies
|
Other computation methodologies approved by the municipality
|
(2)
All calculations consistent with this chapter using the soil cover
complex method shall use the appropriate design rainfall depths for
the various return period storms according to the region for which
they are located as presented in Table C-1 in Appendix C of this chapter.[2] If a hydrologic computer model such as PSRM or HEC-1 is
used for stormwater runoff calculations, then the duration of rainfall
shall be 24 hours. The alternating block method, shown in Figure C-1,
Appendix C of this chapter shall be used for the rainfall distribution.
[2]
Editor's Note: Said appendix is included as an attachment to this chapter.
(3)
For the purposes of existing conditions flow rate determination,
undeveloped land shall be considered as "meadow" in good condition,
unless the natural ground cover generates a lower curve number or
Rational 'C' value (i.e., forest), as listed in Table C-2
or C-3 in Appendix C of this chapter.
(4)
All calculations using the rational method shall use rainfall intensities
consistent with appropriate times-of-concentration for overland flow
and return periods from the design storm curves from PA Department
of Transportation Design Rainfall Curves (1986) (Figures C-2 to C-4).
Times-of-concentration for overland flow shall be calculated using
the methodology presented in Chapter 3 of Urban Hydrology for Small
Watersheds, NRCS, TR-55 (as amended or replaced from time to time
by NRCS). Times-of-concentration for channel and pipe flow shall be
computed using Manning's equation.
(5)
Runoff curve numbers (CN) for both existing and proposed conditions
to be used in the soil cover complex method shall be obtained from
Table C-2 in Appendix C of this chapter.
(6)
Runoff coefficients (c) for both existing and proposed conditions
for use in the rational method shall be obtained from Table C-3 in
Appendix C of this chapter.
(7)
Where uniform flow is anticipated, the Manning equation shall be
used for hydraulic computations, and to determine the capacity of
open channels, pipes, and storm sewers. Values for Manning's
roughness coefficient (n) shall be consistent with Table C-4 in Appendix
C of the chapter.
(8)
Outlet structures for stormwater management facilities shall be designed
to meet the performance standards of this chapter using any generally
accepted hydraulic analysis technique or method.
(9)
The design of any stormwater detention facilities intended to meet
the performance standards of this chapter shall be verified by routing
the design storm hydrograph through these facilities using the storage-indication
method. For drainage areas greater than 200 acres in size, the design
storm hydrograph shall be computed using a calculation method that
produces a full hydrograph. Richland Township may approve the use
of any generally accepted full hydrograph approximation technique
that shall use a total runoff volume that is consistent with the volume
from a method that produces a full hydrograph.
[1]
Editor's Note: Said appendix is included as an attachment to this chapter.
