Township of Upper Burrell, PA
Westmoreland County
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Table of Contents
Table of Contents
A. 
All land development within the Township shall be designed, implemented, operated and maintained to meet the purposes of this chapter, through these two elements:
(1) 
Erosion and sediment control prevention during land development (e.g., earth disturbance during construction); and
(2) 
Water quality protection measures after completion of land development (e.g., postconstruction).
B. 
No approval of any subdivision or land development plans that contain regulated activities, or issuance of any building or occupancy permit, or the commencement of any earth disturbance 5,000 square feet or greater at a project site within the Township, shall proceed until the requirements of this chapter are met, including approval of an individual stormwater management project plan under § 280-10 and a permit under PADEP regulations, where applicable.
(1) 
Exemptions for small developments.
(a) 
At the time of application, the Township shall determine if the subdivision/land development qualifies as a small development and, therefore, is eligible for a simplified stormwater management project plan submission.
(b) 
For the purpose of this chapter, a "small development" is any subdivision or land development which results (or will result when fully developed) in the creation of 5,000 square feet or less of impervious area and one acre or less of any land cover changes.
(c) 
Small development project plans shall be designed in accordance with the requirements set forth in § 280-15 of this chapter.
C. 
All best management practices (BMPs) used to meet the requirements of this chapter shall conform to the design criteria contained in § 280-12 and shall use the calculation methods as described in § 280-13.
A. 
All regulated earth disturbance activities shall be subject to standards and possible permit requirements by PADEP under regulations at 25 Pa. Code Chapter 102. All projects that disturb greater than one acre of area with a point source discharge to surface waters of the commonwealth will need to obtain a National Pollution Discharge Elimination System (NPDES) permit for stormwater discharges associated with construction activities from the Westmoreland County Conservation District prior to the issuance of a building permit.
B. 
Work within natural drainageways shall be subject to permit by PADEP under 25 Pa. Code Chapter 105.
C. 
Any stormwater management facility that would be located in or adjacent to surface waters of the commonwealth, including wetlands, shall be subject to permit by PADEP under 25 Pa. Code Chapter 105.
D. 
Any stormwater management facility that would be located within, or discharge onto, a state highway right-of-way, shall be subject to approval by the Pennsylvania Department of Transportation (PennDOT).
E. 
Culverts, bridges, storm sewers or any other facilities which must pass or convey flows from the tributary area and any facility which may constitute a dam, shall be subject to permit by PADEP under 25 Pa. Code Chapter 105.
A. 
Any person conducting any land development activities in the Township involving earth disturbance of 5,000 square feet or greater shall submit and obtain approval from the Township of a project plan, in accordance with § 280-14 or 280-15, as applicable, that meets the requirements of this chapter, prior to commencing any construction activity, except as exempted herein, under § 280-8B.
B. 
The project plan shall describe the BMPs for erosion and sediment control, and the postconstruction BMPs for water quality protection.
C. 
The project plan shall follow the design criteria and calculation methodology contained in §§ 280-12 and 280-13, respectively.
D. 
The requirements in this section apply to the total land development project, even if it is to take place in stages.
A. 
The project plan shall describe how these water quality protection requirements will be met. Infiltration BMPs shall be evaluated and utilized to the maximum extent possible to manage the net change in stormwater runoff generated so that postconstruction discharges do not degrade the physical, chemical or biological characteristics of the receiving waters.
B. 
Postconstruction stormwater infiltration of runoff shall replicate preconstruction infiltration of runoff to the maximum extent possible.
C. 
In calculating the volume of runoff that can be infiltrated at a site, the following methodology shall be used:
(1) 
Methodology:
Rev = [(S)(Rv)(A)]/12
Where:
Rev
=
Recharge volume (acre-feet)
S
=
Soil-specific recharge factor (inches); see table below
Rv
=
Volumetric runoff coefficient [0.05 + 0.009(I)], where I is the impervious surface percentage (impervious area divided by total project area) x 100%
A
=
Site area contributing to the recharge facility (acres)
Hydrologic Soil Group (HSG)
Soil Specific Recharge Factor(s)
(inches)
A
0.38
B
0.25
C
0.13
D
0.06
If more than one hydrologic soil group is present at a site, a composite recharge volume shall be computed based upon the proportion of total site area within each hydrologic soil group.
(2) 
In selecting the appropriate infiltration BMPs, the applicant shall consider the following:
(a) 
Permeability and infiltration rate of the site soils.
(b) 
Slope and depth to bedrock.
(c) 
Seasonal high water table.
(d) 
Proximity to building foundations and wellheads.
(e) 
Erodibility of soils.
(f) 
Land availability and topography.
(3) 
A detailed soils evaluation of the project site shall be performed to determine the suitability of infiltration BMPs. The evaluation shall be performed by a qualified professional, and at a minimum, address soil permeability, depth to bedrock, susceptibility to sinkhole formation, and subgrade stability. The general process for designing the infiltration BMP shall be:
(a) 
Analyze hydrologic soil groups (HSG) as well as natural and man-made features within the watershed to determine general areas of suitability for infiltration BMPs.
(b) 
Provide field testing data to determine appropriate percolation rate and/or hydraulic connectivity.
(c) 
Design infiltration BMPs for required stormwater volume based on field-determined capacity at the level of the proposed infiltration surface.
(4) 
Soil characteristics, as subject to the specific considerations in Subsection C(7) below:
(a) 
Infiltration BMPs are particularly appropriate in hydrologic soil groups A and B, as described in the Natural Resources Conservation Service Manual TR-55.
(b) 
Low-erodibility factors ("K" factors) are preferred for the construction of basins.
(c) 
There must be a minimum depth of 48 inches between the bottom of any facility and the seasonal high water table and/or bedrock (limiting zones), except for infiltration BMPs receiving only roof runoff which shall be placed in soils having a minimum depth of 24 inches between the bottom of the facility and the limiting zone.
(d) 
There must be an infiltration and/or percolation rate sufficient to accept the additional stormwater load, and to drain completely as determined by field tests.
(e) 
Infiltration BMPs shall be located a minimum of 10 feet away from the foundation wall of any building, on the downgradient side.
(f) 
The infiltration system shall have positive overflow controls to prevent storage within one foot of the finished surface or grade.
(g) 
Infiltration rates shall not be used in computing the storage volume of the infiltration system.
(h) 
Surface inflows shall be designed to prevent direct discharge of sediment into the infiltration system.
(5) 
The recharge volume provided at the site shall be directed to the most permeable hydrologic soil group (HSG) available, except where other considerations apply, such as in limestone geology.
(6) 
Any infiltration BMP shall be capable of completely infiltrating the impounded water within 48 hours.
(7) 
Extreme caution shall be exercised where infiltration is proposed in geologically susceptible areas such as:
(a) 
Strip mines;
(b) 
Where salt or chloride may be applied in deicing and other winter applications, causing groundwater pollution since soils do little to filter this pollutant; and
(c) 
Landslide-susceptible soils, i.e., those found in Table III-2.
(8) 
During the period of land disturbance, runoff shall be controlled prior to entering any proposed infiltration area, and areas proposed for infiltration BMPs shall be protected from sedimentation and compaction during the construction phase, so as to maintain their maximum infiltration capacity.
(9) 
Infiltration BMPs shall not be constructed nor receive runoff until the entire contributory drainage area to the infiltration BMP has received final stabilization.
A. 
Applicants may select a combination of runoff control techniques which are most suitable to control stormwater runoff from the site. All controls shall be subject to approval of the Westmoreland County Conservation District. The Conservation District may request specific information on design and/or operating features of the proposed stormwater controls in order to determine their suitability and adequacy in terms of the standards of this section.
B. 
General standards. The following general standards shall be applied to all development within Upper Burrell Township to promote flow attenuation, erosion and sediment control and flood control.
(1) 
Roof drains are not encouraged to be connected to streets or storm sewers.
(2) 
Runoff shall not be discharged directly onto adjacent property without the written consent of the adjacent landowner in the form of a recorded drainage easement.
(3) 
Postconstruction rates of runoff from any regulated activity shall not exceed the peak rates of preconstruction runoff for the following four different storm frequencies: two-, ten-, twenty-five-, and one-hundred-year.
C. 
The applicant shall consider the effect of the proposed stormwater management techniques on any special soil conditions or geological hazards which may exist on the development site. In the event that such conditions are identified on the site, the Westmoreland County Conservation District may require in-depth studies by a competent geotechnical engineer.
D. 
The stormwater management BMPs shall be selected according to the following order of preference:
(1) 
Site planning for locating proposed buildings, impervious areas and grading which minimizes disruption of the natural site characteristics.
(2) 
Minimization of impervious areas and earthwork.
(3) 
Implementation of nonstructural measures.
(4) 
Infiltration of runoff on-site.
(5) 
Flow attenuation by use of open vegetated swales and natural depressions.
(6) 
Stormwater detention/retention structures.
E. 
All BMPs shall be designed in accordance with the requirements in the Pennsylvania Stormwater Best Management Practices Manual, Document Number: 363-0300-002, effective date: December 30, 2006, or latest revision. A copy is available at the Township or from PADEP.
F. 
Any BMP which is a dam, culvert, stream enclosure or outfall as defined in 25 Pa. Code Chapter 105 shall be designed according to the requirements in those regulations.
G. 
Any stormwater BMP which does not constitute a dam under 25 Pa. Code Chapter 105, and is designed to store runoff and requiring a berm or earthen embankment (i.e., detention basin), shall be designed to satisfy the following:
(1) 
All basins shall be designed to provide for a twenty-four-hour extended detention of the difference between the postconstruction storm and the preconstruction storm (i.e., the postconstruction stormwater runoff will be released over a minimum 24 hours at the ten-year preconstruction rate). Also the basin shall be designed to assure that all other postconstruction peak discharge rates do not exceed the preconstruction discharge rates for the associated required design storms, as specified in § 280-12 of this chapter.
(2) 
Berms and earthen embankments shall be designed to provide an emergency spillway to handle flow up to and including the one-hundred-year post-development conditions.
(3) 
Berms and earthen embankments shall be designed to provide a minimum 1.0 foot of freeboard above the maximum pool elevation computed when the facility functions for the one-hundred-year postconstruction inflow.
(4) 
The slope of all basins shall not exceed three feet horizontal to one foot vertical, and may be further reduced if the soil has unstable characteristics, upon recommendation of the Westmoreland County Conservation District.
(5) 
The minimum top of berm width shall be eight feet.
(6) 
Outlet pipes shall have a minimum diameter of 15 inches.
(7) 
Properly spaced antiseep collars shall be installed on all basin outlet pipes. Design calculations shall be provided in the project plan.
(8) 
The bottom of all basins shall slope, at 1% minimum, towards an outlet control structure, and/or an underdrain system shall be installed to ensure that the basin totally dewaters within 48 hours of the cessation of the storm.
(9) 
A fence, with a minimum height of six feet, must be installed around all basins. A ten-foot-wide gate with lock and keys must be provided to allow access for future maintenance.
H. 
All stormwater conveyance facilities shall be designed to satisfy the following:
(1) 
Water obstructions shall convey runoff from the twenty-five-year postconstruction design storm, at a minimum, and shall have a minimum of 1.0 foot of freeboard measured below the lowest point along the top of the roadway, without damage to the drainage structure or the roadway.
(2) 
Roadway crossings located within designated floodplain areas must be able to convey runoff from the one-hundred-year postconstruction design storm with a minimum of 1.0 foot of freeboard measured below the lowest point along the top of the roadway, without damage to the drainage structure or the roadway.
(3) 
Drainage conveyances must be able to convey, without damage to the drainage structure or roadway, runoff from the twenty-five-year postconstruction design storm without surcharging inlets, where appropriate.
(4) 
Adequate erosion and sediment control protection shall be provided along all open channels, and at all points of discharge.
I. 
The design of all stormwater management facilities and BMPs shall incorporate sound engineering principals and practices. The Township shall reserve the right to disapprove any design that would result in the occurrence or continuation of an adverse hydrologic or hydraulic condition within the watershed.
A. 
Runoff calculations for the preconstruction and postconstruction comparison shall consider the following four different storm frequencies: two-, ten-, twenty-five-, and one-hundred-year.
B. 
Stormwater runoff from all preconstruction and postconstruction sites shall be calculated using either the Rational Method or a Soil Cover Complex methodology.
C. 
Any stormwater runoff calculations involving areas greater than 200 acres, including on- and off-site areas, shall use a generally accepted calculation technique that is based on the NRCS Soil Cover Complex method. Table III-1 (below) summarizes acceptable computation methods. All methods will be selected by the design professional based on the individual limitations and suitability of each method for a particular site, and approved by the Westmoreland County Conservation District. These assumptions shall be used in runoff calculations:
(1) 
Average antecedent moisture conditions.
(2) 
Type II distribution storm.
(3) 
Meadow in good condition shall be used in predevelopment runoff calculations for all areas of existing cultivation.
(4) 
All undeveloped areas other than cultivation shall use the land cover condition which existed during the past 10 consecutive years.
(5) 
All areas to be disturbed during construction and subsequently returned to open space will be assumed to be reduced one hydrologic group category level for postdevelopment.
(6) 
If the initial condition of the site is undeveloped land, the land use shall be considered as "meadow" unless the natural land cover is proven to generate lower runoff curve numbers or Rational "C" value, such as forested lands.
(7) 
Twenty percent of existing impervious area, when present, shall be considered meadow in good condition in predevelopment runoff calculations for redevelopment.
D. 
All calculations consistent with this chapter using the Soil Cover Complex method shall be based on the following twenty-four-hour storm events:
Storm Event
Rainfall
(inches)
(source: NOAA)
2-year
2.45
10-year
3.40
25-year
4.00
100-year
5.05
E. 
All calculations using the Rational Method shall use rainfall intensities in inches per hour consistent with appropriate times of concentration for overland flow and return periods from the Design Storm Curves from the PennDOT Region 2, Pennsylvania Rainfall Intensity-Duration-Frequency Chart shown in the Pennsylvania Department of Transportation Design Manual, Part 2, January 1990, or latest revision thereof. These charts are attached hereto as an appendix and are made a part hereof.
F. 
If a hydrologic computer model such as TR-20, PSRM or HEC-HMS is used for stormwater runoff calculations, then the duration of rainfall shall be 24 hours.
G. 
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.
H. 
Runoff Curve Numbers (CN) for both existing and proposed conditions to be used in the Soil Cover Complex method shall be obtained from Chapter 2 of Urban Hydrology for Small Watersheds, NRCS, TR-55 (as amended or replaced from time to time by NRCS).
I. 
Runoff coefficient (C) for both existing and proposed conditions for use in the Rational Method shall be obtained from any generally accepted hydrologic reference, as approved by the Westmoreland County Conservation District.
J. 
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 obtained from any generally accepted hydrologic/hydraulic reference, as approved by the Westmoreland County Conservation District.
K. 
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, as approved by the Westmoreland County Conservation District.
L. 
The design of any stormwater detention facilities intended to meet the performance standards of this chapter shall be verified by routing the design storm hydrographs through these facilities using the Storage-Indication Method. For drainage areas greater than 20 acres in size, the design storm hydrographs shall be computed using a calculation method that produces a full hydrograph. The Township may approve the use of any generally accepted full hydrograph approximation technique, which shall use a total runoff volume that is consistent with the volume from a method that produces a full hydrograph.
M. 
The Township may require that computed existing runoff rates be reconciled with field observations and conditions. If the design professional can substantiate through actual physical calibration that more appropriate runoff and time-of-concentration values should be utilized at a particular site, then appropriate variations may be made upon review and recommendations of the Westmoreland County Conservation District. Calibration shall require detailed gauge and rainfall data for the particular site in question.
Table III-1
Acceptable Computation Methodologies for Stormwater Management Plans
Method
Method Developed By
Applicability
TR-20 or commercial package based on TR-20
USDA-NRCS
When use of full model is desirable or necessary
TR-55 or commercial package based on TR-55
USDA-NRCS
Applicable for plans within the models limitations
HEC-1
U.S. Army Corps of Engineers
When full model is desirable or necessary
PSRM
Penn State University
When full model is desirable or necessary
Rational Method or commercial package based on rational method
Emil Kuiching (1889)
For sites less than 200 acres
Other methods
Various
As approved by the Westmoreland County Conservation District
Table III-2
Soils Found in Landslide Susceptible Areas
Abbreviation
Soil Name
ErC
Ernest silt loam, 8-15% slopes
FaD
Fairpoint very channery silt loam, 3-8% slopes
GcB
Gilpin channery silt loam, 3-8% slopes
GcC
Gilpin channery silt loam, 8-15% slopes
GcD
Gilpin channery silt loam, 15-25% slopes
GcF
Gilpin channery silt loam, 25-75% slopes
GuB
Gilpin Upshur complex, 3-8% slopes
GuC
Gilpin Upshur complex, 8-15% slopes
GuD
Gilpin Upshur complex, 15-25% slopes
GuF
Gilpin Upshur complex, 25-75% slopes
GwF
Gilpin-Weikert channery loam, 25-75% slopes
Ho
Holly silt loam
MeD
Matewan channery loam, 15-25% slopes
ShF
Shelocta-Gilpin channery silt loam, 25-75% slopes
UwD
Urban land-Wharton complex, 8-25% slopes
VaB
Vandergrift silt loam, 3-8% slopes
VaC
Vandergrift silt loam, 8-15% slopes
VaD
Vandergrift silt loam, 15-25% slopes