[HISTORY: Adopted by the Borough Council of the Borough of
Slippery Rock 8-2-2011 by Ord. No. 656. Amendments noted where
applicable.]
This chapter shall be generally known and referred to as the
"Stormwater Management Ordinance."
A.
In the Borough of Slippery Rock, all regulated activities and all
activities that may affect stormwater runoff, including land development
and earth disturbance activity, are subject to regulation by this
chapter.
B.
Earth disturbance activities and associated stormwater management
controls are also regulated under existing state law and implementing
regulations. This chapter shall operate in coordination with those
parallel requirements; the requirements of this chapter shall be no
less restrictive than state law.
C.
"Regulated activities" are any earth disturbance activities or any
activities that involve the alteration or development of land in a
manner that may affect stormwater runoff. Regulated activities include,
but are not limited to, the following listed items:
(1)
Earth disturbance activities.
(2)
Land development.
(3)
Subdivision.
(4)
Construction of new or additional impervious or semipervious surfaces.
(5)
Construction of new buildings or additions to existing buildings.
(6)
Diversion or piping of any natural or man-made stream channel.
(7)
Installation of stormwater management facilities or appurtenances
thereto.
(8)
Installation of stormwater BMPs.
Approvals issued and actions taken pursuant to this chapter
do not relieve the applicant of the responsibility to comply with
or to secure required permits or approvals for activities regulated
by any other applicable codes, laws, rules, statutes, or ordinances.
To the extent that this chapter imposes more rigorous or stringent
requirements for stormwater management, the specific requirements
contained in this chapter shall be followed.
Notwithstanding any provision(s) of this chapter, including
exemptions, any landowner or any person engaged in the alteration
or development of land which may affect stormwater runoff characteristics
shall implement such measures as are reasonably necessary to prevent
injury to health, safety, or other property. Such measures also shall
include actions as are required to manage the rate, volume, direction,
and quality of resulting stormwater runoff in a manner which otherwise
adequately protects health, property, and water quality.
A.
Neither the granting of any approval under this chapter, nor the
compliance with the provisions of this chapter, or with any condition
imposed by a municipal official hereunder, shall relieve any person
from any responsibility for damage to persons or property resulting
therefrom, or as otherwise imposed by law, nor impose any liability
upon the Borough for damages to persons or property.
B.
The granting of a permit which includes any stormwater management
facilities shall not constitute a representation, guarantee or warranty
of any kind by the Borough, or by an official or employee thereof,
of the practicability or safety of any structure, use or other plan
proposed and shall create no liability upon or cause of action against
such public body, official or employee for any damage that may result
pursuant thereto.
A.
For the purpose of this chapter, certain terms and words used herein
shall be interpreted as follows:
(1)
Words used in the present tense include the future tense; the singular
number includes the plural; and the plural number includes the singular;
words of masculine gender include feminine gender; and words of feminine
gender include masculine gender.
(2)
The word "includes" or "including" shall not limit the term to the
specific example but is intended to extend its meaning to all other
instances of like kind and character.
(3)
The word "person" includes an individual, firm, association, organization,
partnership, trust, company, corporation, or any other similar entity.
(4)
The words "shall" and "must" are mandatory; the words "may" and "should"
are permissive.
(5)
The words "used or occupied" include the words "intended, designed,
maintained, or arranged to be used, occupied or maintained."
B.
ACCELERATED EROSION
AGRICULTURAL ACTIVITIES
ALTERATION
APPLICANT
BEST MANAGEMENT PRACTICES (BMPs)
CHANNEL EROSION
CISTERN
CONSERVATION DISTRICT
CULVERT
DAM
DESIGNEE
DESIGN STORM
DETENTION BASIN
DETENTION VOLUME
DEVELOPER
DEVELOPMENT SITE (SITE)
DISTURBED AREA
DOWNSLOPE PROPERTY LINE
DRAINAGE CONVEYANCE FACILITY
DRAINAGE EASEMENT
DRAINAGEWAY
EARTH DISTURBANCE ACTIVITY
EROSION
EROSION AND SEDIMENT POLLUTION CONTROL PLAN
EXCEPTIONAL-VALUE WATERS
EXISTING CONDITIONS
FEMA
FLOOD
FLOOD-FRINGE
FLOODPLAIN
FLOODWAY
FOREST MANAGEMENT/TIMBER OPERATIONS
FREEBOARD
GRADE
GROUNDWATER RECHARGE
HEC-HMS MODEL CALIBRATED
HIGH-QUALITY WATERS
HYDROLOGIC SOIL GROUP (HSG)
IMPERVIOUS SURFACE (IMPERVIOUS AREA)
IMPOUNDMENT
INFILTRATION STRUCTURES
INLET
LAND DEVELOPMENT (DEVELOPMENT)
(1)
(2)
(3)
LOW-IMPACT DEVELOPMENT (LID)
MAIN STEM (MAIN CHANNEL)
MANNING EQUATION (MANNING FORMULA)
MUNICIPALITY
NATIONAL POLLUTANT DISCHARGE ELIMINATION SYSTEM (NPDES)
NOAA ATLAS 14
NONPOINT SOURCE POLLUTION
NRCS
OPEN CHANNEL
OUTFALL
OUTLET
PADEP
PARKING LOT STORAGE
PEAK DISCHARGE
PERSON
PERVIOUS AREA
PIPE
PLANNING COMMISSION
POINT SOURCE
PROBABLE MAXIMUM FLOOD (PMF)
PROJECT SITE
QUALIFIED PROFESSIONAL
RATIONAL FORMULA
REDEVELOPMENT
REGULATED ACTIVITIES
REGULATED EARTH DISTURBANCE ACTIVITY
RELEASE RATE
RELEASE RATE DISTRICT
RETENTION BASIN
RETENTION VOLUME/REMOVED RUNOFF
RETURN PERIOD
RIPARIAN BUFFER
RISER
ROAD MAINTENANCE
ROOFTOP DETENTION
RUNOFF
RUNOFF CAPTURE VOLUME
SEDIMENT
SEDIMENTATION
SEDIMENT BASIN
SEDIMENT POLLUTION
SEEPAGE PIT/SEEPAGE TRENCH
SEPARATE STORM SEWER SYSTEM
SHEET FLOW
SOIL COVER COMPLEX METHOD
SPILLWAY (EMERGENCY)
STATE WATER QUALITY REQUIREMENTS
STORAGE INDICATION METHOD
STORM FREQUENCY
STORM SEWER
STORMWATER
STORMWATER HOTSPOT
STORMWATER MANAGEMENT FACILITIES
STORMWATER MANAGEMENT PLAN
STORMWATER MANAGEMENT SITE PLAN (SWM SITE PLAN)
STREAM ENCLOSURE
SUBDIVISION
SUBWATERSHED AREA
SWALE
TIMBER OPERATIONS
TIME OF CONCENTRATION (Tc)
USDA
WATERCOURSE
WATERSHED
WATERS OF THE COMMONWEALTH
WETLAND
Terms defined. As used in this chapter, the following terms shall
have the meanings indicated:
The removal of the surface of the land through the combined
action of human activity and natural processes at a rate greater than
would occur because of the natural process alone.
Activities associated with agriculture such as agricultural
cultivation, agricultural operation, and animal heavy use areas. This
includes the work of producing crops, tillage, land clearing, plowing,
disking, harrowing, planting, harvesting crops, or pasturing and raising
of livestock and installation of conservation measures. Construction
of new buildings or impervious area is not considered an agricultural
activity.
As applied to land, a change in topography as a result of
the moving of soil and rock from one location or position to another;
changing of surface conditions by causing the surface to be more or
less impervious; land disturbance.
A landowner, developer, or other person who has filed an
application for approval to engage in any regulated activities at
a project site within the Borough.
Activities, facilities, designs, measures or procedures used
to manage stormwater impacts from regulated activities, to meet state
water quality requirements, to promote groundwater recharge and to
otherwise meet the purposes of this chapter. Stormwater BMPs are commonly
grouped into one of two broad categories or measures: "nonstructural"
or "structural." "Nonstructural" BMPs are measures referred to as
operational and/or behavior-related practices that attempt to minimize
the contact of pollutants with stormwater runoff, whereas "structural"
BMPs are measures that consist of a physical device or practice that
is installed to capture and treat stormwater runoff. "Structural"
BMPs include, but are not limited to, a wide variety of practices
and devices, from large-scale retention ponds and constructed wetlands,
to small-scale underground treatment systems, infiltration facilities,
filter strips, low-impact design, bioretention, wet ponds, permeable
paving, grassed swales, riparian or forested buffers, sand filters,
detention basins, and manufactured devices. "Structural" stormwater
BMPs are permanent appurtenances to the project site.
The widening, deepening, and headward cutting of small channels
and waterways, due to erosion caused by moderate to large floods.
An underground reservoir or tank used for storing rainwater.
The Butler County Conservation District. The Butler County
Conservation District has the authority under a delegation agreement
executed with the Department of Environmental Protection to administer
and enforce all or a portion of the regulations promulgated under
25 Pa. Code Chapter 102.
A structure with appurtenant works that carries a stream
and/or stormwater runoff under or through an embankment or fill.
An artificial barrier, together with its appurtenant works,
constructed for the purpose of impounding or storing water or another
fluid or semifluid, or a refuse bank, fill or structure for highway,
railroad or other purposes which does or may impound water or another
fluid or semifluid.
The agent of this Borough and/or agent of the governing body
involved with the administration, review or enforcement of any provisions
of this chapter by contract or memorandum of understanding.
The magnitude and temporal distribution of precipitation
from a storm event measured in probability of occurrence (e.g., a
twenty-five-year storm) and duration (e.g., 24 hours), used in the
design and evaluation of stormwater management systems. Also see "return
period."
An impoundment structure designed to manage stormwater runoff
by temporarily storing the runoff and releasing it at a predetermined
rate.
The volume of runoff that is captured and released into waters
of the commonwealth at a controlled rate.
A person, partnership, association, corporation, or other
entity, or any responsible person therein or agent thereof, that undertakes
any regulated activity of this chapter.
The specific tract of land for which a regulated activity
is proposed. Also see "project site."
An unstabilized land area where an earth disturbance activity
is occurring or has occurred.
That portion of the property line of the lot, tract, or parcels
of land being developed, located such that all overland or pipe flow
from the site would be directed toward it.
A stormwater management facility designed to convey stormwater
runoff and shall include streams, channels, swales, pipes, conduits,
culverts, storm sewers, etc.
A right granted by a landowner to a grantee, allowing the
use of private land for stormwater management, drainage, or conveyance
purposes.
Any natural or artificial watercourse, trench, ditch, pipe,
swale, channel, or similar depression into which surface water flows.
A construction or other human activity which disturbs the
surface of the land, including, but not limited to, clearing and grubbing,
grading, excavations, embankments, land development, agricultural
plowing or tilling, timber harvesting activities, road maintenance
activities, mineral extraction, and the moving, depositing, stockpiling,
or storing of soil, rock or earth materials.
The movement of soil particles by the action of water, wind,
ice, or other natural forces.
A plan which is designed to minimize accelerated erosion
and sedimentation.
Surface waters of high quality, which satisfies Pa. Code Title 25, Environmental Protection, Chapter 93, Water Quality Standards, § 93.4b(b) (relating to anti-degradation).
The initial condition of a project site prior to the proposed
construction. If the initial condition of the site is undeveloped
land and not forested, the land use shall be considered as meadow,
unless the natural land cover is documented to generate lower curve
numbers or rational "C" coefficient.
The Federal Emergency Management Agency.
A general, temporary condition of partial or complete inundation
of normally dry land areas from the overflow of streams, rivers, and
other waters of the commonwealth.
The remaining portions of the one-hundred-year floodplain
outside of the floodway boundary.
Any land area susceptible to inundation by water from any
natural source or delineated by applicable Department of Housing and
Urban Development, Federal Insurance Administration, Flood Hazard
Boundary Maps as being a special flood hazard area. Included are lands
adjoining a river or stream that have been or may be inundated by
a one-hundred-year flood. Also included are areas that comprise Group
13 soils, as listed in Appendix A of the Pennsylvania Department of
Environmental Protection (PADEP) Technical Manual for Sewage Enforcement
Officers (as amended or replaced from time to time by PADEP).
The channel of the watercourse and those portions of the
adjoining floodplains that are reasonably required to carry and discharge
the one-hundred-year frequency flood. Unless otherwise specified,
the boundary of the floodway is as indicated on maps and flood insurance
studies provided by FEMA. In an area where no FEMA maps or studies
have defined the boundary of the one-hundred-year frequency floodway,
it is assumed, absent evidence to the contrary, that the floodway
extends from the stream to 50 feet landward from the top of the bank
of the stream.
Planning and activities necessary for the management of forestland.
These include timber inventory and preparation of forest management
plans, silvicultural treatment, cutting budgets, logging road design
and construction, timber harvesting, site preparation and reforestation.
A vertical distance between the elevation of the design high
water and the top of a dam, levee, tank, basin, or diversion ridge.
The space is required as a safety margin in a tank, pond or basin.
A slope, usually of a road, channel or natural ground, specified
in percent and shown on plans as specified herein.
Replenishment of existing natural underground water supplies.
(Hydrologic Engineering Center Hydrologic Modeling System)
A computer-based hydrologic modeling technique adapted to the watershed(s)
in Butler County for the Act 167 plan. The model has been calibrated
by adjusting key model input parameters.
Surface water having quality which exceeds levels necessary to support propagation of fish, shellfish, and wildlife and recreation in and on the water by satisfying Pa. Code Title 25, Environmental Protection, Chapter 93, Water Quality Standards, § 93.4b(a).
Infiltration rates of soils vary widely and are affected
by subsurface permeability as well as surface intake rates. Soils
are classified into one of four HSG (A, B, C, and D) according to
their minimum infiltration rate, which is obtained for bare soil after
prolonged wetting. The Natural Resource Conservation Service (NRCS)
of the United States Department of Agriculture defines the four groups
and provides a list of most of the soils in the United States and
their group classification. The soils in the area of interest may
be identified from a soil survey report from the local NRCS office
or the County Conservation District.
A surface that prevents the infiltration of water into the
ground. "Impervious surface" (or areas) includes, but is not limited
to, roofs, additional indoor living spaces, patios, garages, storage
sheds and similar structures, parking or driveway areas, and any new
streets and sidewalks. Any surface areas proposed to initially be
gravel or crushed stone shall be assumed to be impervious surfaces.
A retention or detention basin designed to retain stormwater
runoff and release it at a controlled rate.
A structure designed to direct runoff into the ground (e.g.,
french drains, seepage pits, seepage trench, etc.).
A surface connection to a closed drain. A structure at the
diversion end of a conduit. The upstream end of any structure through
which water may flow.
The improvement of one lot or two or more contiguous lots, tracts
or parcels of land for any purpose involving a group of two or more
buildings or the division or allocation of land or space between or
among two or more existing or prospective occupants by means of, or
for the purpose of, streets, common areas, leaseholds, condominiums,
building groups, or other features;
Any subdivision of land;
Development in accordance with Section 503(1.1) of the PA Municipalities
Planning Code.[1]
An approach to land development that uses various land planning
and design practices and technologies to simultaneously conserve and
protect natural resource systems and reduce infrastructure costs.
LID still allows land to be developed, but in a cost-effective manner
that helps mitigate potential environmental impacts.
Any stream segment or other runoff conveyance facility used
as a reach in the Butler County Act 167 watershed hydrologic model(s).
A method for calculation of velocity of flow (e.g., feet
per second) and flow rate (e.g., cubic feet per second) in open channels
based upon channel shape, roughness, depth of flow and slope. "Open
channels" may include closed conduits so long as the flow is not under
pressure.
The Borough of Slippery Rock, Butler County, Pennsylvania.
The federal government's system for issuance of permits
under the Clean Water Act,[2] which is delegated to PADEP in Pennsylvania.
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 (2004). NOAA's
Atlas 14 can be accessed at internet address http://hdsc.nws.noaa.gov/hdsc/pfds/.
Pollution that enters a water body from diffuse origins in
the watershed and does not result from discernible, confined, or discrete
conveyances.
Natural Resource Conservation Service [previously Soil Conservation
Service (SCS)].
A drainage element in which stormwater flows with an open
surface. Open channels include, but shall not be limited to, natural
and man-made drainageways, swales, streams, ditches, canals, and pipes
not under pressure.
Points of water disposal from a stream, river, lake, tidewater,
or artificial drain.
The Pennsylvania Department of Environmental Protection.
Involves the use of impervious parking areas as temporary
impoundments with controlled release rates during rainstorms.
The maximum rate of stormwater runoff from a specific storm
event.
An individual, partnership, public or private association
or corporation, or a governmental unit, public utility or any other
legal entity whatsoever which is recognized by law as the subject
of rights and duties.
Any area not defined as "impervious."
A culvert, closed conduit, or similar structure (including
appurtenances) that conveys stormwater.
The Planning Commission of the Borough of Slippery Rock.
Any discernible, confined, or discrete conveyance, including,
but not limited to, any pipe, ditch, channel, tunnel, or conduit from
which stormwater is or may be discharged, as defined in state regulations
at 25 Pa. Code § 92a.2.[3]
The flood that may be expected from the most severe combination
of critical meteorological and hydrologic conditions that are reasonably
possible in any area. The PMF is derived from the probable maximum
precipitation (PMP) as determined on the basis of data obtained from
the National Oceanographic and Atmospheric Administration (NOAA).
The specific area of land where any regulated activities
in the municipality are planned, conducted, or maintained.
Any person licensed by the Pennsylvania Department of State
or otherwise qualified by law to perform the work required by this
chapter.
A rainfall-runoff relation used to estimate peak flow.
Earth disturbance activities on land which has previously
been developed.
Any earth disturbance activities or any activities that involve
the alteration or development of land in a manner that may affect
stormwater runoff.
The percentage of predevelopment peak rate of runoff from
a site or subwatershed area to which the post-development peak rate
of runoff must be reduced to protect downstream areas.
Those subwatershed areas in which post-development flows
must be reduced to a certain percentage of predevelopment flows as
required to meet the plan requirements and the goals of Act 167.
An impoundment in which stormwater is stored and not released
during the storm event. Stored water may be released from the basin
at some time after the end of the storm.
The volume of runoff that is captured and not released directly
into the surface waters of this commonwealth during or after a storm
event.
The average interval, in years, within which a storm event
of a given magnitude can be expected to recur. For example, the twenty-five-year
return period rainfall would be expected to recur on the average once
every 25 years; or, stated in another way, the probability of a twenty-five-year
storm occurring in any one given year is 0.04 (i.e., a four-percent
chance).
A vegetated area bordering perennial and intermittent streams
and wetlands that serves as a protective filter to help protect streams/wetlands
from the impacts of adjacent land uses.
A vertical pipe extending from the bottom of a pond that
is used to control the discharge rate from the pond for a specified
design storm.
Earth disturbance activities within the existing road right-of-way,
such as grading and repairing existing unpaved road surfaces, cutting
road banks, cleaning or clearing drainage ditches, and other similar
activities. Road maintenance activities that do not disturb the subbase
of a paved road (such as milling and overlays) are not considered
earth disturbance activities.
Temporary ponding and gradual release of stormwater falling
directly onto flat roof surfaces by incorporating controlled-flow
roof drains into building designs.
Any part of precipitation that flows over the land surface.
The volume of runoff that is captured (retained) and not
released into surface waters of the commonwealth during or after a
storm event.
Soils or other materials transported by surface water as
a product of erosion.
The process by which mineral or organic matter is accumulated
or deposited by the movement of water.
A barrier, dam, retention or detention basin located and
designed to retain rock, sand, gravel, silt, or other material transported
by stormwater runoff.
The placement, discharge, or any other introduction of sediment
into waters of the commonwealth occurring from the failure to properly
design, construct, implement or maintain control measures and control
facilities in accordance with the requirements of this chapter.
An area of excavated earth filled with loose stone or similar
coarse material, into which surface water is directed for infiltration
into the ground.
A conveyance or system of conveyances (including roads with
drainage systems, municipal streets, catch basins, curbs, gutters,
ditches, man-made channels, or storm drains) primarily used for collecting
and conveying stormwater runoff.
Runoff that flows over the ground surface as a thin, even
layer, not concentrated in a channel.
A method of runoff computation developed by the NRCS that
is based on relating soil type and land use/cover to a runoff parameter
called "curve number" (CN).
A depression in the embankment of a pond or basin, or other
overflow structure, that is used to pass peak discharges greater than
the maximum design storm controlled by the pond or basin.
The regulatory requirements to protect, maintain, reclaim,
and restore water quality under Title 25 of the Pennsylvania Code
and the Clean Streams Law.[6]
A reservoir routing procedure based on solution of the continuity
equation (inflow minus outflow equals the change in storage), with
outflow defined as a function of storage volume and depth.
The number of times that a given storm event occurs or is
exceeded on the average in a stated period of years. See also "return
period."
A system of pipes and/or open channels that convey intercepted
runoff and stormwater from other sources, but excludes domestic sewage
and industrial wastes.
Runoff from the surface of the land resulting from precipitation,
snow, or ice melt.
A land use or activity that generates higher concentrations
of hydrocarbons, trace metals, or toxicants than are found in typical
stormwater runoff.
Any structure, natural or man-made, that, due to its condition,
design, or construction, conveys, stores, or otherwise affects stormwater
runoff. Typical stormwater management facilities include, but are
not limited to, detention and retention basins, open channels, storm
sewers, pipes and infiltration facilities.
The Butler County Stormwater Management Plan for managing
stormwater runoff in Butler County as required by the Act of October
4, 1978, P.L. 864 (Act 167), and known as the "Storm Water Management
Act."[7]
The plan prepared by the applicant or his representative
indicating how stormwater runoff will be managed at the project site
in accordance with this chapter.
A bridge, culvert, or other structure in excess of 100 feet
in length upstream to downstream which encloses regulated waters of
the commonwealth.
The division or redivision of a lot, tract, or parcel of
land by any means into two or more lots, tracts, parcels or other
divisions of land, including changes in existing lot lines for the
purpose, whether immediate or future, of lease, transfer of ownership,
or building or lot development; provided, however, that the subdivision
by lease of land for agricultural purposes into parcels of more than
10 acres, not involving any new street or easement of access or any
residential dwellings, shall be exempt (Pennsylvania Municipalities
Planning Code, Act of July 31, 1968, P.L. 805, No. 247[8]).
The smallest drainage unit of a watershed for which stormwater
management criteria has been established in the stormwater management
plan.
A low-lying stretch of land that gathers or carries surface
water runoff.
See "forest management."
The time for surface runoff to travel from the hydraulically
most distant point of the watershed to a point of interest within
the watershed. This time is the combined total of overland flow time
and flow time in pipes or channels, if any.
The United States Department of Agriculture.
A channel or conveyance of surface water, such as a stream
or creek, having defined bed and banks, whether natural or artificial,
with perennial or intermittent flow.
Area drained by a river, watercourse, or other surface water,
whether natural or artificial.
Rivers, streams, creeks, rivulets, impoundments, ditches,
watercourses, storm sewers, lakes, dammed water, wetlands, ponds,
springs and other bodies or channels of conveyance of surface and
underground water, or parts thereof, whether natural or artificial,
within or on the boundaries of the Commonwealth of Pennsylvania.
Those areas that are inundated or saturated by surface water
or groundwater at a frequency and duration sufficient to support,
and that under normal circumstances do support, a prevalence of vegetation
typically adapted for life in saturated soil conditions, including
swamps, marshes, bogs and similar areas. (The term includes but is
not limited to wetland areas listed in the state water plan, the United
States Forest Service Wetlands Inventory of Pennsylvania and a wetland
area designated by a river basin commission. This definition is used
by the United States Environmental Protection Agency and the United
States Army Corps of Engineers.)
A.
For all regulated activities, unless specifically exempted in § 338-8:
(1)
Preparation and implementation of an approved SWM site plan is required.
(2)
No regulated activities shall commence until the Borough issues written
approval of a SWM site plan, which demonstrates compliance with the
requirements of this chapter.
(4)
The SWM site plan approved by the Borough shall be on site throughout
the duration of the regulated activities.
B.
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 (including
but not limited to Chapter 102, Erosion and Sediment Control) and
the Clean Streams Law.[1] Various BMPs and their design standards are listed in
the Erosion and Sediment Pollution Control Program Manual (E&S
Manual), No. 363-2134-008 (April 15, 2000), as amended and updated.
[1]
Editor's Note: See 35 P.S. § 691.1 et seq.
C.
For all regulated activities, stormwater BMPs shall be designed,
installed, 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 and the Clean Streams Law, conform
to the state water quality requirements, meet all requirements under
the Storm Water Management Act[2] and any more stringent requirements as determined by the
Borough.
[2]
Editor's Note: See 32 P.S. § 680.1 et seq.
D.
The Borough may, after consultation with PADEP and the Conservation
District, 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.
All regulated activities shall include, to the maximum extent practicable,
measures to:
(1)
Protect health, safety, and property.
(2)
Meet the water quality goals of this chapter by implementing measures
to:
(a)
Minimize disturbance to floodplains, wetlands, natural slopes,
existing native vegetation and woodlands.
(b)
Create, maintain, or extend riparian buffers and protect existing
forested buffers.
(c)
Provide trees and woodlands adjacent to impervious areas whenever
feasible.
(d)
Minimize the creation of impervious surfaces and the degradation
of waters of the commonwealth and promote groundwater recharge.
(e)
Protect natural systems and processes (drainageways, vegetation,
soils, and sensitive areas) and maintain, as much as possible, the
natural hydrologic regime.
(f)
Incorporate natural site elements (wetlands, stream corridors,
mature forests) as design elements.
(g)
Avoid erosive flow conditions in natural flow pathways.
(h)
Minimize soil disturbance and soil compaction.
(i)
Minimize thermal impacts to waters of the commonwealth.
(j)
Disconnect impervious surfaces by directing runoff to pervious
areas, wherever possible, and decentralize and manage stormwater at
its source.
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 developments 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.
If diffused flow is proposed to be concentrated and discharged onto
adjacent property, the applicant must document that adequate downstream
conveyance facilities exist to safely transport the concentrated discharge,
or otherwise prove that no erosion, sedimentation, flooding, or other
harm will result from the concentrated discharge.
H.
Stormwater drainage systems shall be provided in order to permit
unimpeded flow along natural watercourses, except as modified by stormwater
management facilities or open channels consistent with this chapter.
I.
Where watercourses traverse a development site, drainage easements
(with a minimum width of 20 feet and include the one-hundred-year
water surface) shall be provided conforming to the line of such watercourses.
The terms of the easement shall prohibit excavation, the placing of
fill or structures, and any alterations that may adversely affect
the flow of stormwater within any portion of the easement. Also, maintenance,
including mowing of vegetation within the easement, may be required,
except as approved by the appropriate governing authority.
J.
When it can be shown that, due to topographic conditions, natural drainageways on the site cannot adequately provide for drainage, open channels may be constructed conforming substantially to the line and grade of such natural drainageways. Work within natural drainageways shall be subject to approval by PADEP under regulations at 25 Pa. Code Chapter 105 through the joint permit application process, or, where deemed appropriate by PADEP, through the general permit process.
K.
Any stormwater management facilities or any facilities that constitute water obstructions (e.g., culverts, bridges, outfalls, or stream enclosures, etc.) that are regulated by this chapter, that will be located in or adjacent to waters of the commonwealth (including wetlands), shall be subject to approval by PADEP under regulations at 25 Pa. Code Chapter 105 through the joint permit application process, or, where deemed appropriate by PADEP, the general permit process. When there is a question whether wetlands may be involved, it is the responsibility of the applicant or his agent to show that the land in question cannot be classified as wetlands; otherwise, approval to work in the area must be obtained from PADEP.
M.
Any stormwater management facilities regulated by this chapter that
will be located on or discharged onto state highway rights-of-way
shall be subject to approval by the Pennsylvania Department of Transportation
(PennDOT).
N.
Minimization of impervious surfaces and infiltration of runoff through
seepage beds, infiltration trenches, etc., are encouraged, where soil
conditions and geology permit, to reduce the size or eliminate the
need for detention facilities.
O.
Infiltration BMPs must be dispersed throughout the site, 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.
P.
The design of facilities over karst shall include an evaluation and
implementation of measures to minimize adverse effects.
Q.
Roof drains shall not be connected to streets, sanitary or storm
sewers, or roadside ditches in order 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 the Borough shall permit it on a case-by-case
basis.
R.
Applicants are encouraged to use low-impact development practices
to reduce the costs of complying with the requirements of this chapter
and the state water quality requirements.
S.
When stormwater management facilities are proposed within 1,000 feet
of a downstream municipality, the developer shall notify the downstream
municipality and provide a copy of the SWM plan, if requested, for
review and comment.
B.
The applicant must demonstrate that the following BMPs are being
utilized to the maximum extent practicable to receive consideration
for the exemptions:
(1)
Design around and limit disturbance of floodplains, wetlands, natural
slopes over 15%, existing native vegetation, and other sensitive and
special value features.
(2)
Maintain riparian and forested buffers.
(3)
Limit grading and maintain nonerosive flow conditions in natural
flow paths.
(4)
Maintain existing tree canopies near impervious areas.
(5)
Minimize soil disturbance and reclaim disturbed areas with topsoil
and vegetation.
(6)
Direct runoff to pervious areas.
C.
The applicant must demonstrate that the proposed development/additional
impervious area will not adversely impact the following:
D.
An applicant proposing regulated activities may be eligible for exemption
from rate control, volume control, or stormwater management site plan
requirements in this chapter according to the following table:
|
Table 807.1
| ||
|---|---|---|
|
Exemptions and Submission Requirements
| ||
|
New Impervious Area1, 2
(square footage)
|
Applicant Must Provide
| |
|
0 < 2,500
|
No submission is required
| |
|
2,500 < 5,000
|
Documentation of new impervious surfaces3
| |
|
5,000 and greater
|
Rate controls, volume controls and SWM site plan
| |
|
NOTES:
| ||
|---|---|---|
|
1
|
New impervious area since the date of adoption of this chapter.
| |
|
2
|
Gravel in existing condition shall be considered pervious, and
gravel in proposed condition shall be considered impervious.
| |
|
3
|
The small project stormwater management application adopted
by resolution of Borough Council shall be used to document new impervious
surfaces.
| |
E.
Single-family residential activities.
(1)
Single-family
residential activities are exempt from these requirements, provided
the construction:
(b)
Has buildings set back 75 feet from downstream property lines; and
(2)
The Borough can require more information or require mitigation of
certain impacts through installation of stormwater management BMPs
if there is a threat to property, health, or safety.
F.
An applicant proposing regulated activities, after demonstrating compliance with § 338-8A, B and C, may be exempted from various requirements of this chapter if documentation can be provided that a downstream man-made water body (i.e., reservoir, lake, or man-made wetlands) has been designed or modified to address the potential stormwater flooding impacts of the proposed development.
G.
The purpose of this section is to ensure consistency of stormwater
management planning between local ordinances and NPDES permitting
(when required) and to ensure that the applicant has a single and
clear set of stormwater management standards to which the applicant
is subject. The Borough may accept alternative stormwater management
controls under this section, provided that:
(1)
The Borough, in consultation with the PADEP (or delegated authority), determines that meeting the volume control requirements (See § 338-10.) is not possible or places an undue hardship on the applicant.
(2)
The alternative controls are documented to be acceptable to PADEP
(or delegated authority) for NPDES requirements pertaining to post-construction
stormwater management requirements.
H.
Agricultural activities 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.
I.
Forest management and timber operations are exempt from the rate
and volume control requirement and SWM site plan preparation requirement
of this chapter, provided the activities are performed according to
the requirements of 25 Pa. Code Chapter 102. It should be noted that
temporary roadways are not exempt.
J.
The Borough may deny or revoke any exemption pursuant to this section
at any time for any project that the Borough believes may pose a threat
to public health, safety, property or the environment.
A.
The provisions of this chapter are the minimum standards for the
protection of the public welfare.
B.
All waiver requests must meet the provisions of Subsections G and H of this section. Waivers shall not be issued from implementing such measures as necessary to meet state water quality standards and requirements; protect health, safety, and property; meet special requirements for high-quality (HQ) and exceptional-value (EV) watersheds. Municipalities will then consider waivers in accordance with § 338-7D.
C.
If an applicant demonstrates to the satisfaction of the governing
body of the Borough that any mandatory provision of this chapter is
unreasonable or causes unique or undue unreasonableness or hardship
as it applies to the proposed project, or that an alternate design
may result in a superior result within the context of the findings
and purposes of this chapter, the governing body of the Borough, upon
obtaining the comments and recommendations of the Borough Engineer,
may grant a waiver or relief so that substantial justice may be done
and the public interest is secured, provided that such waiver will
not have the effect of nullifying the intent and purpose of this chapter.
D.
The applicant shall submit all requests for waivers in writing and
shall include such requests as a part of the plan review and approval
process. The applicant shall state in full the facts of unreasonableness
or hardship on which the request is based, the provision or provisions
of this chapter that are involved, and the minimum waiver or relief
that is necessary. The applicant shall state how the requested waiver
and how the applicant's proposal shall result in an equal or
better means of complying with the intent or purpose and general principles
of this chapter.
E.
The Borough shall keep a written record of all actions on waiver
requests.
F.
The Borough may charge a fee for each waiver request, which shall
be used to offset the administrative costs of reviewing the waiver
request. The applicant shall also agree to reimburse the Borough for
reasonable and necessary fees that may be incurred by the Borough
Engineer in any review of a waiver request.
G.
In granting waivers, the Borough may impose reasonable conditions
that will, in its judgment, secure substantially the objectives of
the standards or requirements that are to be modified.
H.
The Borough may grant applications for waivers when the following
findings are made, as relevant:
(1)
That the waiver shall result in an equal or better means of complying
with the intent of this chapter.
(2)
That the waiver is the minimum necessary to provide relief.
(3)
That the applicant is not requesting a waiver based on cost considerations.
(4)
That existing downgradient stormwater problems will not be exacerbated.
(5)
That runoff is not being diverted to a different drainage area.
(6)
That increased flooding or ponding on off-site properties or roadways
will not occur.
(7)
That potential icing conditions will not occur.
(8)
That increase of peak flow or volume from the site will not occur.
(9)
That erosive conditions due to increased peak flows or volume will
not occur.
(10)
That adverse impact to water quality will not result.
(11)
That increased one-hundred-year floodplain levels will not result.
(12)
That increased or unusual municipal maintenance expenses will
not result from the waiver.
(13)
That the amount of stormwater generated has been minimized to
the greatest extent allowed.
(14)
That infiltration of runoff throughout the proposed site has
been provided where practicable, and predevelopment groundwater recharge
protected.
(15)
That peak flow attenuation of runoff has been provided.
(16)
That long-term operation and maintenance activities are established.
(17)
That the receiving streams and/or water bodies will not be adversely
impacted in flood-carrying capacity, aquatic habitat, channel stability
and erosion and sedimentation.
B.
Stormwater runoff volume controls shall be implemented using the
Design Storm Method or the Simplified Method as defined below. For
regulated activity areas equal or less than one acre that do not require
hydrologic routing to design the stormwater facilities, this chapter
establishes no preference for either method; therefore, the applicant
may select either method 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 BMP Manual) is applicable to
any sized regulated activity. This method requires detailed modeling
based on site conditions.
(a)
Do not increase the post-development total runoff volume when
compared to the predevelopment total runoff volume for the two-year/twenty-four-hour
storm event.
(b)
For hydrologic modeling purposes:
[1]
Existing nonforested pervious areas must be considered meadow
(good condition) for predevelopment hydrologic calculations.
[2]
Twenty percent of existing impervious area, when present within
the proposed project site, shall be considered meadow (good condition)
for predevelopment hydrologic calculations for redevelopment.
(2)
The Simplified Method (CG-2 in the BMP Manual) 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 one acre or for projects that require detailed 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 surface waters of the 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 0.5 inch of the permanently
removed runoff should be infiltrated.
(d)
Actual field infiltration tests at the location of the proposed
elevation of the stormwater BMPs are required. Infiltration tests
shall be conducted in accordance with the BMP Manual. Notification
of the Borough shall be provided to allow witnessing of the testing.
(3)
In cases where it is not possible or desirable to use infiltration-based best management practices to partially fulfill the requirements in either Subsection B(1) or (2) of this section, the following procedure shall be used:
(a)
At a minimum, the following documentation shall be provided
to justify the decision to not use infiltration BMPs:
[1]
Description of and justification for field infiltration/permeability
testing with respect to the type of test and test locations.
[2]
An interpretive narrative describing existing site soils and
their structure as these relate to the interaction between soils and
water occurring on the site. In addition to providing soil and soil
profile descriptions, this narrative shall identify depth to seasonal
high-water tables and depth to bedrock, and provide a description
of all subsurface elements (fragipans and other restrictive layers,
geology, etc.) that influence the direction and rate of subsurface
water movement.
[3]
A qualitative assessment of the site's contribution to
annual aquifer recharge shall be made, along with identification of
any restrictions or limitations associated with the use of engineered
infiltration facilities.
[4]
The provided documentation must be signed and sealed by a professional
engineer or geologist.
(b)
The following water quality pollutant load reductions will be
required for all disturbed areas within the proposed development:
|
Pollutant Load
|
Units
|
Required Reduction
| |
|---|---|---|---|
|
Total suspended solids (TSS)
|
Pounds
|
85%
| |
|
Total phosphorous (TP)
|
Pounds
|
85%
| |
|
Total nitrate (NO3)
|
Pounds
|
50%
|
(c)
The performance criteria for water quality best management practices
shall be determined from the Pennsylvania Stormwater Best Management
Practices Manual, most current version.
C.
The applicable worksheets from the BMP Manual must be used in calculations
to establish volume control.
A.
Lands contained within Butler County that have not had release rates
established under an approved Act 167 stormwater management plan:
(1)
Post-development discharge rates shall not exceed the predevelopment
discharge rates for the one-, two-, ten-, twenty-five-, fifty-, and
one-hundred-year storms.
B.
Lands contained within Butler County that have had release rates
established under an approved Act 167 stormwater management plan:
A.
Sensitive areas and water quality sensitive developments as defined
below which require special consideration with regard to stormwater
management.
(1)
"Sensitive areas" are defined as those areas that, if developed,
have the potential to endanger a water supply. These areas consist
of the delineated one-year zone of contribution and direct upslope
areas tributary to the water supply wells. Municipalities may update
the sensitive area boundaries based on new research or studies as
required.
(2)
"Stormwater hotspots" are defined as a land development project that
has a high potential to endanger local water quality and could potentially
threaten groundwater reservoirs. The Municipal Engineer will determine
what constitutes these classifications on a case-by-case basis. The
PADEP wellhead protection contaminant source list shall be used as
a guide in these determinations. Industrial manufacturing site and
hazardous material storage areas must provide NPDES SIC codes.
B.
Performance standards.
(1)
The location of the boundaries of sensitive areas is set by drainage
areas tributary to any public water supply. The exact location of
these boundaries as they apply to a given development site shall be
determined using mapping at a scale which accurately defines the limits
of the sensitive area. If the project site is within the sensitive
area (in whole or in part), two-foot contour interval mapping shall
be provided to define the limits of the sensitive area. If the project
site is adjacent to but within 500 linear feet of a defined sensitive
area, a five-foot contour interval map defining the limits of the
sensitive area shall be included in the stormwater management plan
to document the site's location relative to the sensitive area.
(2)
Stormwater hotspots may be required to prepare and implement a stormwater
pollution prevention plan and file notice of intent as required under
the provisions of the EPA Industrial Stormwater NPDES Permit Requirements.
(3)
Stormwater hotspots must use an acceptable pretreatment BMP prior
to volume control and/or rate control BMPs. Acceptable pretreatment
BMPs for these developments include those based on filtering, settling,
or chemical reaction processes such as coagulation.
A.
The applicant shall meet requirements as contained in 25 Pa. Code
Chapters 92a and 102, as required and applicable, as follows:[1]
B.
Evidence of any necessary plan or permit approval for earth disturbance
activities from PADEP or the Butler County Conservation District must
be provided to the Borough of Slippery Rock as part of any final plan
submission.
C.
A copy of the approved erosion and sediment control plan and any
other permit, as required by PADEP or the Butler County Conservation
District, shall be available at the project site at all times if required
under Chapter 102.
A.
For any regulated activity within a protected watershed (high-quality or exceptional-value), the applicant shall meet requirements as contained in 25 Pa. Code Chapter 93 as required and applicable.
B.
An existing resources and site analysis plan shall be prepared to
provide the developer and the Borough with a comprehensive analysis
of existing conditions, both on the proposed development site and
within 500 feet of the site. Conditions beyond the parcel boundaries
may be described on the basis of existing published data available
from governmental agencies and from aerial photographs. The Borough
shall review the plan to assess its accuracy, conformance with Borough
ordinances, and likely impact upon the natural and cultural resources
on the property. The following information shall be required:
(1)
Complete current perimeter boundary survey of the property to be
subdivided or developed prepared by a registered surveyor, showing
all courses, distances, and area and tie-ins to all adjacent intersections.
(2)
A vertical aerial photograph enlarged to a scale not less detailed
than one inch equals 400 feet, with the site boundaries clearly marked.
(3)
Natural features, including:
(a)
Contour lines at intervals of not more than two feet. (Ten-foot
intervals are permissible beyond the parcel boundaries, interpolated
from USGS published maps.) Contour lines shall be based on information
derived from a topographic survey for the property, evidence of which
shall be submitted, including the date and source of the contours.
Datum to which contour elevations refer and references to known, established
bench marks and elevations shall be included on the plan.
(b)
Steep slopes in the following ranges: 15% to 25%, 25% and greater.
The location of these slopes shall be graphically depicted by category
on the plan. Slope shall be measured over three or more two-foot contour
intervals.
(c)
Areas within the floodway, flood-fringe, and approximated floodplain.
(d)
Watercourses, either continuous or intermittent and named or
unnamed, and lakes, ponds or other water features as depicted on the
USGS Quadrangle Map, most current edition.
(e)
Wetlands and wetland margins.
(f)
Riparian buffers.
(g)
Soil types and their boundaries, as mapped by the USDA Natural
Resource Conservation Service, including a table listing the soil
characteristics pertaining to suitability for construction and, in
unsewered areas, for septic suitability. Alluvial and hydric soils
shall specifically be depicted on the plan.
(h)
Existing vegetation, denoted by type, including woodlands, hedgerows,
tree masses, tree lines, individual freestanding trees over six inches
DBH, wetland vegetation, pasture or croplands, orchards, permanent
grassland, old fields, and any other notable vegetative features on
the site. Vegetative types shall be described by plant community,
relative age, and condition.
(i)
Any identified Pennsylvania Natural Diversity Inventory (PNDI)
site conflicts.
(j)
Geologic formations on the tract, including rock outcroppings,
cliffs, sinkholes, and fault lines, based on available published information
or more detailed data obtained by the applicant.
(4)
Existing man-made features, including:
(a)
Location, dimensions, and use of existing buildings and driveways.
(b)
Location, names, widths, center-line courses, paving widths,
identification numbers, and rights-of-way of existing streets and
alleys.
(c)
Location of trails that have been in public use (pedestrian,
equestrian, bicycle, etc.).
(d)
Location and size of existing sanitary sewage facilities.
(e)
Location and size of drainage facilities.
(f)
Location of water supply facilities, including wellhead protection
areas.
(g)
Any easements, deed restrictions, rights-of-way, or any other
encumbrances upon the land, including location, size, and ownership.
(h)
Site features or conditions such as hazardous waste, dumps,
underground tanks, active and abandoned wells, quarries, landfills,
sand mounds, and artificial land conditions.
(5)
Total acreage of the tract, the adjusted tract area, where applicable,
and the constrained land area with detailed supporting calculations.
C.
Stormwater management system concept plan. A written and graphic
concept plan of the proposed post-development stormwater management
system shall be prepared and include:
(1)
Preliminary selection and location of proposed structural stormwater
controls;
(2)
Location of existing and proposed conveyance systems such as grass
channels, swales, and storm drains;
(3)
Location of floodplain/floodway limits;
(4)
Relationship of site to upstream and downstream properties and drainages;
(5)
Preliminary location of proposed stream channel modifications, such
as bridge or culvert crossings.
D.
Consultation meeting. Prior to any stormwater management permit application
submission, the landowner or developer shall meet with the Borough
for a consultation meeting on a concept plan for the post-development
stormwater management system to be utilized in the proposed project.
This consultation meeting shall take place at the time of the preliminary
plan or other early step in the development process. The purpose of
this meeting is to discuss the post-development stormwater management
measures necessary for the proposed project, as well as to discuss
and assess constraints, opportunities and potential ideas for stormwater
management designs before the formal site design engineering is commenced.
F.
SWM plan and report shall address the following:
(1)
Design using nonstructural BMPs:
(a)
Lot configuration and clustering:
(b)
Minimum disturbance:
[1]
Define disturbance zones (excavation/grading) for the site and
individual lots to protect maximum total site area from disturbance.
[2]
Barriers/flagging proposed to protect designated nondisturbance
areas.
[3]
Considered mitigative practices for minimal disturbance areas
(e.g., soil restoration).
[4]
Considered reforestation and revegetation opportunities.
(2)
Apply structural BMP selection process that meets runoff quantity
and quality needs:
(a)
Manage close to source with collection with conveyance minimized.
(b)
Consistent with site factors (e.g., soils, slope, available
space, amount of sensitive areas, pollutant removal needs).
(c)
Minimize footprint and integrate into already disturbed areas/other
building program components (e.g., recharge beneath parking areas,
vegetated roofs).
(d)
Consider other benefits such as aesthetic, habitat, recreational
and educational benefits.
(e)
BMPs selected based on maintenance needs that fit owner/users.
(f)
BMPs sustainable using a long-term maintenance plan.
A.
General design guidelines.
(1)
Stormwater shall not be transferred from one watershed to another,
unless:
(2)
Consideration shall be given to the relationship of the subject property
to the drainage pattern of the watershed. A concentrated discharge
of stormwater to an adjacent property shall be within an existing
watercourse or confined in an easement or returned to a predevelopment
flow type condition.
(3)
Innovative stormwater BMPs and recharge facilities are encouraged
(e.g., rooftop storage, dry wells, cisterns, recreation area ponding,
diversion structures, porous pavements, holding tanks, infiltration
systems, in-line storage in storm sewers, and grading patterns). They
shall be located, designed, and constructed in accordance with the
latest technical guidance published by PADEP, provided they are accompanied
by detailed engineering plans and performance capabilities and supporting
site-specific soils, geology, runoff and groundwater and infiltration
rate data to verify proposed designs. Additional guidance from other
sources may be accepted at the discretion of the Municipal Engineer
(a preapplication meeting is suggested).
(4)
All existing and natural watercourses, channels, drainage systems
and areas of surface water concentration shall be maintained in their
existing condition unless an alteration is approved by the appropriate
regulatory agency.
(5)
The design of all stormwater management facilities shall incorporate
sound engineering principles and practices. The Borough shall reserve
the right to disapprove any design that would result in the continuation
or exacerbation of a documented adverse hydrologic or hydraulic condition
within the watershed, as identified in the plan.
(6)
The design and construction of multiple-use stormwater detention
facilities are strongly encouraged. In addition to stormwater management,
facilities should, where appropriate, allow for recreational uses,
including ball fields, play areas, picnic grounds, etc. Consultation
with the Borough and prior approval are required before design. Provision
for permanent wet ponds with stormwater management capabilities may
also be appropriate.
(a)
Multiple-use basins should be constructed so that potentially
dangerous conditions are not created.
(b)
Water quality basins or recharge basins that are designed for
a slow release of water or other extended detention ponds are not
permitted for recreational uses, unless the ponded areas are clearly
separated and secure.
B.
Stormwater management facility design considerations. All stormwater
management facilities shall meet the following design requirements:
(1)
No outlet structure from a stormwater management facility, or swale,
shall discharge directly onto a municipal or state roadway without
approval from the Borough or PennDOT.
(2)
The top, or toe, of any slope shall be located a minimum of 10 feet
from any property line.
(3)
The minimum horizontal distance between any stormwater holding facility
shall be 25 feet. The lowest floor elevation of any structure constructed
immediately adjacent to a detention basin or other stormwater facility
shall be a minimum of two feet above the one-hundred-year water surface
elevation.
(4)
Stormwater management facility bottom (or surface of permanent pool)
elevations must be greater than adjacent floodplain elevations (FEMA
or HEC-RAS analysis). If no floodplain is defined, bottom elevations
must be greater than existing ground elevations 50 feet from top of
stream bank in the facility's vicinity.
(5)
Basin outflow culverts discharging into floodplains must account
for tailwater. Tailwater corresponding to the one-hundred-year-floodplain
elevation must be used for all design storms, or the applicant may
elect to determine flood elevations of the adjacent watercourse for
each design storm. The floodplain is assumed to be 50 feet from top
of stream bank in areas where a floodway is not designated, or no
other evidence is provided.
(6)
The invert of all stormwater management facilities and underground
infiltration/storage facilities shall be located a minimum of two
feet above the seasonal high groundwater table. The invert of stormwater
facilities may be lowered if adequate subsurface drainage is provided.
Flows from underdrains need not be accounted for in volume or rate
control calculations.
(7)
Whenever possible, the side slopes and basin shape shall be amenable
to the natural topography. Vertical side slopes and rectangular basins
shall be avoided whenever possible.
(8)
Exterior slopes of compacted soil shall not exceed 3:1 and may be
further reduced if the soil has unstable characteristics.
(9)
Interior slopes of the basin shall not exceed 3:1.
(10)
Unless specifically designed as a volume control facility, all
stormwater management facilities shall have a minimum slope of 2%
extending radially out from the principal outlet structure. Facilities
designed as water quality/infiltration BMPs may have a bottom slope
of zero.
(11)
Impervious low-flow channels are not permitted within stormwater
management facilities.
(12)
Unless specifically designed as a volume control or water quality
facility, all stormwater management facilities must empty over a period
of time not less than 24 hours and not more than 72 hours from the
end of the facility's inflow hydrograph. Infiltration tests performed
at the facility locations and proposed basin bottom depths, in accordance
with the BMP Manual, must support time-to-empty calculations if infiltration
is a factor.
(13)
Energy dissipaters and/or level spreaders shall be installed
at points where pipes or drainageways discharge to or from basins.
Discharges to drainage swales shall be dissipated, or piped, to an
acceptable point.
(14)
Landscaping and planting specifications must be provided for
all stormwater management basins and be specific for each type of
basin.
(a)
Minimal-maintenance, saturation-tolerant vegetation must be
provided in basins designed as water quality/infiltration BMPs.
(15)
A safety fence may be required, at the discretion of the Borough,
for any stormwater management facility. The fence shall be a minimum
of four feet high and of a material acceptable to the Borough. A gate
with a minimum opening of 10 feet shall be provided for maintenance
access.
(16)
Principal outlet structures. The primary outlet structure shall
be designed to pass all design storms (up to and including the one-hundred-year
event) without discharging through the emergency spillway. All principal
outlet structures shall:
(a)
Be constructed of reinforced concrete or an alternative material
approved by the Municipal Engineer. When approved for use, all metal
risers shall:
[1]
Be suitably coated to prevent corrosion.
[2]
Have a concrete base attached with a watertight connection.
The base shall be sufficient weight to prevent flotation of the riser.
[3]
Provide a trash rack or similar appurtenance to prevent debris
from entering the riser.
[4]
Provide an anti-vortex device, consisting of a thin vertical
plate normal to the basin berm.
(b)
Provide trash racks to prevent clogging of primary outflow structure
stages for all orifices.
(c)
Provide outlet aprons and shall extend to the toe of the basin
slope at a minimum.
(17)
Emergency spillways. Any stormwater management facility designed
to store runoff shall provide an emergency spillway designed to convey
the one-hundred-year post-development peak rate flow with a blocked
primary outlet structure. The emergency spillway shall be designed
per the following requirements:
(a)
The top of embankment elevation shall provide a minimum one
foot of freeboard above the maximum water surface elevation. This
is to be calculated when the spillway functions for the one-hundred-year
post-development inflow, with a blocked outlet structure.
(b)
Avoid locating on fill areas, whenever possible.
(c)
The spillway shall be armored to prevent erosion during the
one-hundred-year post-development flow, with a blocked primary outlet
structure.
[1]
Synthetic liners or riprap may be used, and calculations sufficient
to support proposed armor must be provided. An earthen plug must be
used to accurately control the spillway invert if riprap is the proposed
armoring material. Emergency spillway armor must extend up the sides
of the spillway and continue at full width to a minimum of 10 feet
past the toe of slope.
(d)
Municipal Engineer may require the use of additional protection
when slopes exceed 4:1 and spillway velocities might exceed NRCS standards
for the particular soils involved.
(e)
Any underground stormwater management facility (pipe storage
systems) must have a method to bypass flows higher than the required
design (up to a one-hundred-year post-development inflow) without
structural failure or causing downstream harm or safety risks.
(18)
Stormwater management basins. Design of stormwater management
facilities having three feet or more of water depth (measured vertically
from the lowest elevation in the facility to the crest of the emergency
spillway) shall meet the following additional requirements:
(a)
The maximum water depth within any stormwater management facility
shall be no greater than eight feet when functioning through the primary
outlet structure.
(c)
A ten-foot-wide access to the basin bottom must be provided
with a maximum longitudinal slope of 10%.
(d)
Berms shall be constructed using soils that conform to the unified
soil classification of CH, MH, CL or ML. Soils used shall be tested
to determine its density analysis per ASTM 698. The embankments will
be constructed in a maximum of six-inch lifts. The lifts will each
be compacted to a density at least 98% of its maximum dry density.
Each layer of compacted fill shall be tested to determine its density
per ASTM 2922 or ASTM 3017. One test per 50 cubic yards of material
placed (at least one per layer) shall be performed by an independent
testing agency.
(e)
A cutoff and key trench of impervious material shall be provided
under all embankments four feet or greater in height. The cutoff trench
shall run the entire length of the embankment and tie into undisturbed
natural ground.
(f)
Antiseep collars, or a PADEP-approved alternative, must be provided
on all outflow culverts in accordance with the methodology contained
in the latest edition of the PADEP E&S Manual. An increase in
seepage length of 15% must be used in accordance with the requirements
for permanent antiseep collars.
(19)
Construction of stormwater management facilities:
(a)
Basins used for rate control only shall be installed prior to
or concurrent with any earthmoving or land disturbances which they
will serve. The phasing of their construction shall be noted in the
narrative and on the plan.
(b)
Basins that include water quality or recharge components shall
have those components installed in such a manner as to not disturb
or diminish their effectiveness.
(c)
Compaction test reports shall be kept on file at the site and
be subject to review at all times, with copies being forwarded to
the Municipal Engineer upon request.
(d)
Temporary and permanent grasses or stabilization measures shall
be established on the sides and base of all earthen basins within
15 days of construction.
(20)
Exceptions to these requirements may be made at the discretion
of the Borough for BMPs that retain or detain water but are of a much
smaller scale than traditional stormwater management facilities.
C.
Stormwater-carrying facilities.
(1)
All storm sewer pipes, grass waterways, open channels, swales and
other stormwater-carrying facilities that service drainage areas within
the site must be able to convey post-development runoff from the ten-year
design storm.
(2)
Stormwater management facilities that convey off-site water through
the site shall be designed to convey the twenty-five-year storm event
(or larger events, as determined by the Municipal Engineer).
(3)
All developments shall include provisions that allow for the overland
conveyance and flow of the post-development one-hundred-year storm
event without damage to public or private property.
(4)
Storm sewers.
(a)
Storm sewers must be able to convey post-development runoff
without surcharging inlets for the ten-year storm event.
(b)
When connecting to an existing storm sewer system, the applicant
must demonstrate that the proposed system will not exacerbate any
existing stormwater problems and that adequate downstream capacity
exists.
(c)
Inlets, manholes, pipes, and culverts shall be constructed in
accordance with the specifications set forth in PennDOT's Publication
408, and as detailed in PennDOT's Publication 72M, Standards
for Roadway Construction (RC), or other detail approved by the Municipal
Engineer. All material and construction details (inlets, manholes,
pipe trenches, etc.) must be shown on the SWM site plan and a note
added that all construction must be in accordance with PennDOT's
Publication 408 and PennDOT's Publication 72M, latest edition.
A note shall be added to the plan stating that all frames, concrete
top units, and grade adjustment rings shall be set in a bed of full
mortar according to Publication 408.
(d)
A minimum pipe size of 15 inches in diameter shall be used in
all roadway systems (public or private) proposed for construction
in the Borough. Pipes shall be designed to provide a minimum velocity
of 2 1/2 feet per second when flowing full, but in all cases,
the slope shall be no less then 0.5%. Arch pipe of equivalent cross-sectional
area may be substituted in lieu of circular pipe where cover or utility
conflict conditions exist.
(e)
All storm sewer pipes shall be laid to a minimum depth of one
foot from subgrade to the crown of pipe.
(f)
In curbed roadway sections, the maximum encroachment of water
on the roadway pavement shall not exceed half of a through travel
lane or one inch less than the depth of curb during the ten-year design
storm of five-minute duration. Gutter depth shall be verified by inlet
capture/capacity calculations that account for road slope and opening
area.
(g)
Standard Type "C" inlets with eight-inch hoods shall be used
along curbed roadway networks. Type "C" inlets with ten-inch hoods
that provide a two-inch sump condition may be used with approval of
the Municipal Engineer when roadway longitudinal slopes are 1.0% or
less.
(h)
For inlets containing a change in pipe size, the elevation for
the crown of the pipes shall be the same, or the smaller pipe's
crown shall be at a higher elevation.
(i)
All inlets shall provide a minimum two-inch drop between the
lowest inlet pipe invert elevation and the outlet pipe invert elevation.
(j)
On curbed sections, a double inlet shall be placed at the low
point of sag vertical curves, or an inlet shall be placed on each
side of the low point at a distance not to exceed 100 feet, or at
an elevation not to exceed 0.2 foot above the low point.
(k)
At all roadway low points, swales and easements shall be provided
behind the curb or swale and through adjacent properties to channelize
and direct any overflow of stormwater runoff away from dwellings and
structures.
(l)
All inlets in paved areas shall have heavy-duty bicycle-safe
grating. A note to this effect shall be added to the SWM site plan
or inlet details therein.
(m)
Inlets must be sized to accept the specified pipe sizes without
knocking out any of the inlet corners. All pipes entering or exiting
inlets shall be cut flush with the inside wall of the inlet. A note
to this effect shall be added to the SWM site plan or inlet details
therein.
(n)
Inlets shall have weep holes covered with geotextile fabric
placed at appropriate elevations to completely drain the subgrade
prior to placing the base and surface course on roadways.
(o)
Inlets, junction boxes, or manholes greater then five feet in
depth shall be equipped with ladder rungs and shall be detailed on
the SWM site plan.
(p)
Inlets shall not have a sump condition in the bottom (unless
designed as a water quality BMP or specifically approved by the Borough).
Pipe shall be flush with the bottom of the box, or concrete channels
shall be poured.
(q)
Accessible drainage structures shall be located on continuous
storm sewer systems at all vertical dislocations, at all locations
where a transition in storm sewer pipe sizing is required, at all
vertical and horizontal angle points exceeding 5°, and at all
points of convergence of two or more storm sewer pipes.
(r)
All storm drainage piping shall be provided with either reinforced
concrete headwalls or end sections of compatible material as the pipe
involved at its entrance and discharge.
(s)
Outlet protection and energy dissipaters shall be provided at
all surface discharge points in order to minimize erosion consistent
with the E&S Manual.
[1]
Flow velocities and volumes from any storm sewer shall not result
in a degradation of the receiving channel.
(t)
Stormwater roof drains and pipes shall not be connected to storm
sewers or discharge onto impervious areas without approval by the
Municipal Engineer.
(5)
Swale conveyance facilities.
(a)
Swales must be able to convey post-development runoff from a
ten-year design storm with six inches of freeboard to top of the swale.
(b)
Swales shall have side slopes no steeper than 3:1.
(c)
All swales shall be designed, labeled on the SWM site plan,
and details provided to adequately construct and maintain the design
dimension of the swales.
(d)
Swales shall be designed for stability using velocity or shear
criteria. Velocity criteria may be used for channels with less than
10% slope. Shear criteria may be used for all swales. Documentation
must be provided to support velocity and/or shear limitations used
in calculations.
(f)
Manning's "n" values used for swale capacity design must
reflect the permanent condition.
A.
All calculations shall be consistent with the guidelines set forth
in the BMP Manual, as amended herein.
B.
Stormwater runoff from all development sites shall be calculated
using either the Rational Method or the NRCS Rainfall-Runoff Methodology.
Other methods shall be selected by the design professional based on
the individual limitations and suitability of each method for a particular
site and approved by the Municipal Engineer.
C.
Rainfall values.
(1)
Rational Method. The Pennsylvania Department of Transportation Drainage
Manual, Intensity-Duration-Frequency Curves, Publication 584, Chapter
7A, latest edition, shall be used in conjunction with the appropriate
time of concentration and return period.
(2)
NRCS Rainfall-Runoff Method. The Soil Conservation Service Type II,
twenty-four-hour rainfall distribution shall be used in conjunction
with rainfall depths from NOAA Atlas 14 or be consistent with the
following table:
|
Return Interval
(years)
|
24-hour Rainfall Total
(inches)
| |
|---|---|---|
|
1
|
2.02
| |
|
2
|
2.41
| |
|
10
|
3.38
| |
|
25
|
4.00
| |
|
50
|
4.50
| |
|
100
|
5.03
|
D.
Runoff volume.
(1)
Rational Method: not to be used to calculate runoff volume.
(2)
NRCS Rainfall-Runoff Method. This method shall be used to estimate
the change in volume due to regulated activities. Combining curve
numbers for land areas proposed for development with curve numbers
for areas unaffected by the proposed development into a single weighted
curve number is not acceptable.
E.
Peak flow rates.
(1)
Rational Method. This method may be used for design of conveyance
facilities only. Extreme caution should be used by the design professional
if the watershed has more than one main drainage channel, if the watershed
is divided so that hydrologic properties are significantly different
in one versus the other, if the time of concentration exceeds 60 minutes,
or if stormwater runoff volume is an important factor. The combination
of Rational Method hydrographs based on timing shall be prohibited.
(2)
NRCS Rainfall-Runoff Method.
(a)
This method is recommended for design of stormwater management
facilities and where stormwater runoff volume must be taken into consideration.
The following provides guidance on the model applicability:
(b)
The NRCS Antecedent Runoff Condition II (ARC II, previously
AMC II) must be used for all simulations. The use of continuous simulation
models that vary the ARC are not permitted for stormwater management
purposes.
(3)
For comparison of peak flow rates, flows shall be rounded to a tenth
of a cubic foot per second (cfs).
F.
Runoff coefficients.
(2)
NRCS Rainfall-Runoff Method. Use Table D-2 (Appendix D). Curve numbers
(CN) should be rounded to tenths for use in hydrologic models as they
are a design tool with statistical variability. For large sites, CNs
should realistically be rounded to the nearest whole number.
(3)
For the purposes of predevelopment peak flow rate and volume determination,
existing nonforested pervious area conditions shall be considered
as meadow (good condition).
(4)
For the purposes of predevelopment peak flow rate and volume determination,
20% of existing impervious area, when present, shall be considered
meadow (good condition).
G.
Design storm.
(1)
All stormwater management facilities shall be verified by routing
the proposed one-year, two-year, ten-year, twenty-five-year, fifty-year,
and one-hundred-year hydrographs through the facility using the Storage
Indication Method or Modified Puls Method. The design storm hydrograph
shall be computed using a calculation method that produces a full
hydrograph.
(2)
The stormwater management and drainage system shall be designed to
safely convey the post-development one-hundred-year storm event to
stormwater detention facilities, for the purpose of meeting peak rate
control.
(3)
All structures (culvert or bridges) proposed to convey runoff under
a municipal road shall be designed to pass the fifty-year design storm
with a minimum one foot of freeboard measured below the lowest point
along the top of the roadway.
H.
Time of concentration.
(1)
The time of concentration is to represent the average condition that
best reflects the hydrologic response of the area. The following time
of concentration (Tc) computational methodologies
shall be used unless another method is preapproved by the Municipal
Engineer:
(a)
Predevelopment: NRCS Lag Equation:
|
Time of concentration = Tc = [(Tlog/0.6) * 60] (minutes)
|
 |
|
Where:
| ||||
|
Tlag
|
=
|
Lag time (hours)
| ||
|
L
|
=
|
Hydraulic length of watershed (feet)
| ||
|
Y
|
=
|
Average overland slope of watershed (percent)
| ||
|
S
|
=
|
Maximum retention in watershed as defined by S = [(1,000/CN)
-10]
| ||
|
CN
|
=
|
NRCS curve number for watershed
| ||
(b)
Post-development: commercial, industrial, or other areas with
large impervious areas (>20% impervious area): NRCS Segmental Method.
The length of sheet flow shall be limited to 100 feet. Tc for channel and pipe flow shall be computed using Manning's
Equation.
(c)
Post-development: residential, cluster, or other low-impact
designs less than or equal to 20% impervious area: NRCS Log Equation
or NRCS Segmental Method.
(2)
Additionally, the following provisions shall apply to calculations
for time of concentration:
(a)
The post-development Tc shall never be
greater that the predevelopment Tc for any
watershed or subwatershed. This includes when the designer has specifically
used swales to reduce flow velocities. In the event that the designer
believes that the post-development Tc is greater,
it will still be set by default equal to the predevelopment Tc for modeling purposes.
(b)
The minimum Tc for any watershed shall
be five minutes.
(c)
The designer may choose to assume a five-minute Tc for any post-development watershed or subwatershed
without providing any computations.
(d)
The designer must provide computations for all predevelopment
Tc paths. A five-minute Tc cannot be assumed for predevelopment.
(e)
Undetained fringe areas (areas that are not tributary to a stormwater
facility but where a reasonable effort has been made to convey runoff
from all new impervious coverage to best management practices) may
be assumed to represent the predevelopment conditions for purpose
of Tc calculation.
I.
Drainage areas tributary to sinkholes or closed depressions in areas
underlain by limestone or carbonate geologic features shall be excluded
from the modeled point of analysis defining predevelopment flows.
If left undisturbed during construction activities, areas draining
to closed depressions may also be used to reduce peak runoff rates
in the post-development analysis. New, additional contributing runoff
should not be directed to existing sinkholes or closed depressions.
J.
Where uniform flow is anticipated, the Manning's Equation shall
be used for hydraulic computations and to determine the capacity of
open channels, pipes, and storm sewers. The Manning's Equation
should not be used for analysis of pipes under pressure flow or for
analysis of culverts. Manning's "n" values shall be obtained
from PennDOT's Drainage Manual, Publication 584. Inlet control
shall be checked at all inlet boxes to ensure the headwater depth
during the ten-year design event is contained below the top of grate
for each inlet box.
K.
The Borough has the authority to require that computed existing runoff
rates be reconciled with field observations, conditions and site history.
If the designer 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 recommendation of the Borough.
For any of the activities regulated by this chapter and not eligible for the exemptions provided in § 338-8, the final approval of subdivision and/or land development plans, the issuance of any building or occupancy permit, or the commencement of any land disturbance activity may not proceed until the applicant has received written approval of a SWM site plan from the Borough.
The SWM site plan and SWM site report shall consist of all applicable calculations, maps, and plans. All SWM site plan materials shall be submitted to the Borough in a format that is clear, concise, legible, neat and well organized; otherwise, the SWM site plan shall be rejected. Appropriate sections from Chapter 350, Subdivision and Land Development, and other applicable local ordinances, shall be followed in preparing the SWM site plan.
A.
SWM site plan shall include, but not be limited to:
(1)
Plans shall be of one size and in a form that meets the requirements
for recording in the office of the Recorder of Deeds of Butler County.
(a)
Plans for tracts of less than 20 acres shall be drawn at a scale
of one inch equals no more than 50 feet;
(b)
Plans for tracts of 20 acres or more shall be drawn at a scale
of one inch equals no more than 100 feet;
(c)
Lettering shall be drawn to a size to be legible if the plans
are reduced to 1/2 size.
(2)
The name of the development; name and location address of the property
site; name, address, and telephone number of the applicant/owner of
the property; and name, address, telephone number, e-mail address,
and engineering seal of the individual preparing the SWM site plan.
(3)
The date of submission and dates of all revisions.
(4)
A graphical and written scale on all drawings and maps.
(5)
A North arrow on all drawings and maps.
(6)
A location map at a minimum scale of one inch equals 1,000 feet which
illustrates the project relative to highways, municipalities or other
identifiable landmarks.
(7)
Metes and bounds description of the entire tract perimeter.
(9)
Perimeters of existing water bodies within the project area, including
stream banks, lakes, ponds, springs, field-delineated wetlands or
other bodies of water, sinkholes, flood hazard boundaries (FEMA-delineated
floodplains and floodways), areas of natural vegetation to be preserved,
the total extent of the upstream area draining through the site, and
overland drainage paths. In addition, any areas necessary to determine
downstream impacts, where required for proposed stormwater management
facilities, must be shown.
(10)
The location of all existing and proposed utilities, on-lot
wastewater facilities, water supply wells, sanitary sewers, and waterlines
on and within 50 feet of property lines, including inlets, manholes,
valves, meters, poles, chambers, junction boxes, and other utility
system components.
(11)
A key map showing all existing man-made features beyond the
property boundary that may be affected by the project.
(12)
Soil names and boundaries with identification of the hydraulic
soil group classification, including rock outcroppings.
(13)
Proposed impervious surfaces (structures, roads, paved areas,
and buildings), including plans and profiles of roads and paved areas
and floor elevations of buildings.
(14)
Existing and proposed land use(s).
(15)
Horizontal alignment, vertical profiles, and cross sections
of all open channels, pipes, swales and other BMPs.
(16)
The location and clear identification of the nature of permanent
stormwater BMPs.
(17)
The location of all erosion and sedimentation control facilities,
shown on a plan separate from the SWM site plan (typically an E&S
plan).
(18)
A minimum twenty-foot-wide access easement around all stormwater
management facilities that would provide ingress to and egress from
a public right-of-way. In lieu of providing an easement to the public
right-of-way, a note may be added to the plan granting the Borough
or its designees access to all easements via the nearest public right-of-way.
(19)
Construction details for all drainage and stormwater BMPs.
(20)
Construction sequence.
(21)
Identification of short-term and long-term ownership, operations,
and maintenance responsibilities.
(22)
Notes and statements.
(a)
A statement, signed by the landowner, acknowledging that the
stormwater BMPs are fixtures that cannot be altered or removed without
prior approval by the Borough.
(b)
A statement referencing the operation and maintenance (O&M)
agreement and stating that the O&M agreement is part of the SWM
site plan.
(c)
A note indicating that record drawings will be provided for
all stormwater facilities prior to occupancy or the release of the
surety bond.
(d)
The following signature block for the registered professional
preparing the stormwater management plan:
|
"I, __________________, hereby certify that the stormwater management
plan meets all design standards and criteria of the Borough of Slippery
Rock's Stormwater Management Ordinance."
|
(e)
The following signature block for the Municipal Engineer reviewing
the stormwater management plan:
|
"I, __________________, have reviewed this stormwater management
plan in accordance with the design standards and criteria of the Borough
of Slippery Rock's Stormwater Management Ordinance."
|
B.
SWM site report shall include (but not be limited to):
(1)
General data, including:
(a)
Project name.
(b)
Project location; address of the property site.
(c)
Name, address, and telephone number of the applicant/owner of
the property.
(d)
Name, address, telephone number, e-mail address, and engineering
seal of the individual preparing the SWM site report.
(e)
Date of submission and revisions.
(2)
Project description narrative that clearly discusses the project
and provides the following information, where applicable:
(a)
Narrative:
[1]
Statement of the regulated activity describing what is being
proposed; overall stormwater management concept with description of
permanent stormwater management techniques, including construction
specifications and materials to be used for stormwater management
facilities.
[2]
Expected project schedule.
[3]
Location map showing the project site and its location relative
to release rate districts.
[4]
Detailed description of the existing site conditions, including
a site evaluation completed for projects proposed in areas of carbonate
geology or karst topography, and other environmentally sensitive areas
such as brownfields.
[5]
Total site area, pre and post, which must be equal or have an
explanation as to why it is not.
[6]
Total site impervious area.
[7]
Total off-site areas.
[8]
Number and description of stormwater management facilities.
[9]
Type of development.
[10]
Predevelopment land use.
[11]
Whether site is a water quality sensitive (WQS) development.
[12]
Whether site is in a defined sensitive area.
[13]
Types of water quality and recharge systems used, if applicable.
[14]
Complete hydrologic, hydraulic, and structural computations
for all stormwater management facilities.
[15]
A written maintenance plan for all stormwater features, including
detention facilities and other stormwater management elements.
[16]
Identification of ownership and maintenance responsibility for
all permanent stormwater management facilities.
[17]
Other pertinent information, as required.
(b)
Summary tables:
[1]
Predevelopment hydrologic soil group (HSG) assumptions, curve
numbers (CN), computation of average slope, hydraulic length, computed
time of concentration.
[2]
Existing condition's runoff volume and peak rate of runoff.
[3]
Post-development runoff volume and peak rate of runoff.
[4]
Undetained areas, areas to ponds.
[5]
Land use for each subarea.
[6]
Hydrologic soil group (HSG) assumptions, curve numbers (CN).
[7]
Time of concentration computed for each subarea.
[8]
Post-development peak rate of runoff routed to ponds and out.
[9]
Pond maximum return period design data, including maximum water
surface elevation, berm elevation, and emergency spillway elevation.
[10]
Water quality depth and volume requirements.
(c)
Calculations:
[1]
Complete hydrologic, hydraulic and structural computations,
calculations, assumptions, and criteria for the design of all stormwater
BMPs.
[2]
Details of the berm embankment and outlet structure indicating
the embankment top elevation, embankment side slopes, top width of
embankment, emergency spillway elevation, perforated riser dimensions,
pipe barrel dimensions and dimensions and spacing of antiseep collars.
[3]
Design computations for the control structures (pipe barrel
and riser, etc.).
[4]
A plot or table of the stage-storage (volume vs. elevation)
and all supporting computations.
[5]
Routing computations.
(3)
Reports that do not clearly indicate the above information may be
rejected for review by the Borough and will be returned to the applicant.
(4)
Description of, justification, and actual field results for infiltration
testing with respect to the type of test and test location for the
design of infiltration BMPs.
(5)
The effect of the project (in terms of runoff volumes, water quality,
and peak flows) on surrounding properties and aquatic features and
on any existing municipal stormwater collection system that may receive
runoff from the project site.
(6)
Description of the proposed changes to the land surface and vegetative
cover, including the type and amount of impervious area to be added.
(7)
Identification of short-term and long-term ownership, operation,
and maintenance responsibilities, as well as schedules and costs for
inspection and maintenance activities for each permanent stormwater
or drainage BMP, including provisions for permanent access or maintenance
easements.
C.
Supplemental information to be provided prior to recording of the
SWM site plan, as applicable:
(1)
Signed and executed operations and maintenance agreement.
(2)
Signed and executed easements, as required for all on-site and off-site
work.
(3)
An erosion and sedimentation control plan and approval letter from
the Butler County Conservation District.
(4)
A NPDES permit.
(5)
Permits from PADEP and ACOE.
(6)
Geologic assessment.
(7)
Soils investigation report, including boring logs, compaction requirements,
and recommendations for construction of detention basins.
(8)
A highway occupancy permit from PennDOT when utilization of a PennDOT
storm drainage system is proposed or when proposed facilities would
encroach onto a PennDOT right-of-way.
A.
The Borough shall require receipt of a complete SWM site plan and
report as specified in this chapter. The Borough shall review the
SWM site plan and report for consistency with the purposes, requirements,
and intent of this chapter.
B.
The Borough shall not approve any SWM site plan and report that is
deficient in meeting the requirements of this chapter. At its sole
discretion and in accordance with this chapter, when a SWM site plan
and report is found to be deficient, the Borough may disapprove the
submission and require a resubmission, or, in the case of minor deficiencies,
the Borough may accept submission of modifications.
C.
The Borough shall notify the applicant in writing within 45 calendar
days whether the SWM site plan and report is approved or disapproved
if the SWM site plan and report is not part of a subdivision or land
development plan. If the SWM site plan and report involves a subdivision
or land development plan, the timing shall follow the subdivision
and land development process according to the Municipalities Planning
Code.[1]
[1]
Editor's Note: See 53 P.S. § 10101 et seq.
D.
The Municipal Building Permit Office shall not issue a building permit
for any regulated activity if the SWM site plan and report has been
found to be inconsistent with this chapter, as determined by the Borough.
All required permits from PADEP must be obtained prior to issuance
of a building permit.
A modification to a submitted SWM site plan and report for a
development site that involves a change in stormwater management facilities
or techniques, or that involves the relocation or redesign of stormwater
management facilities, or that is necessary because soil or other
conditions are not as stated on the SWM site plan as determined by
the Borough, shall require a resubmission of the modified SWM site
plan in accordance with this chapter.
A disapproved SWM site plan and report may be resubmitted, with
the revisions addressing the Borough's concerns documented in
writing, to the Borough in accordance with this chapter. The applicable
municipal review fee must accompany a resubmission of a disapproved
SWM site plan and report.
The Borough's approval of a SWM site plan and report authorizes
the regulated activities contained in the SWM site plan for a maximum
term of validity of five years following the date of approval. The
Borough may specify a term of validity shorter than five years in
the approval for any specific SWM site plan. Terms of validity shall
commence on the date the Borough signs the approval for a SWM site
plan. If stormwater management facilities included in the approved
SWM site plan have not been constructed, or if a record drawing of
these facilities has not been approved within this time, then the
Borough may consider the SWM site plan disapproved and may revoke
any and all permits or approvals.
A.
The applicant shall be responsible for providing record drawings
of all stormwater BMPs included in the approved SWM site plan. The
record drawing and an explanation of any discrepancies with the approved
SWM site plan shall be submitted to the Borough as a prerequisite
for the release of the guarantee or issuance of an occupancy permit.
B.
The record drawing shall include a certification of completion signed
by a qualified professional verifying that all permanent stormwater
BMPs have been constructed according to the approved SWM site plan
and report.
(1)
Drawings shall show all approved revisions and elevations and inverts
to all manholes, inlets, pipes, and stormwater control facilities.
(2)
Submission shall include a comparison of the constructed stage-storage
(volume vs. elevation) of all aboveground and below-ground stormwater
storage facilities to the approved design.
C.
After receipt of the record drawing and certification of completion
by the Borough, the Borough Engineer may conduct a final inspection.
A.
Easements shall be established to accommodate the existence of drainageways.
B.
Where a tract is traversed by a watercourse, drainageway, channel
or stream, there shall be provided an easement paralleling the line
of such watercourse, drainageway, channel or stream with a width adequate
to preserve the unimpeded flow of natural drainage in the one-hundred-year
floodplain.
C.
Easements shall be established for all on-site stormwater management
or drainage facilities, including but not limited to detention facilitates
(above or below ground), infiltration facilities, all stormwater BMPs,
drainage swales, and drainage facilities (inlets, manholes, pipes,
etc.).
D.
Easements are required for all areas used for off-site stormwater
control.
E.
All easements shall be a minimum of 20 feet wide and shall encompass
the one-hundred-year surface elevation of the proposed stormwater
facility.
F.
Easements shall provide ingress to, and egress from, a public right-of-way.
In lieu of providing an easement to the public right-of-way, a note
may be added to the plan granting the Borough or its designee access
to all easements via the nearest public right-of-way able for vehicle
ingress and egress on grades of less than 10% for carrying out inspection
or maintenance activities.
G.
Where possible, easements shall be centered on side and/or rear lot
lines.
H.
Nothing shall be planted or placed within the easement which would
adversely affect the function of the easement or conflict with any
conditions associated with such easement.
I.
All easement agreements shall be recorded with a reference to the
recorded easement indicated on the site plan. The format and content
of the easement agreement shall be reviewed and approved by the Municipal
Engineer and Solicitor.
A.
The applicant shall provide a financial guarantee to the Borough
for the timely installation and proper construction of all stormwater
management controls as required by the approved SWM site plan and
this chapter, equal to 110% of the full construction cost of the required
controls in accordance with the Municipalities Planning Code.[1]
[1]
Editor's Note: See 53 P.S. § 10101 et seq.
B.
At the completion of the project and as a prerequisite for the release
of the financial guarantee, the applicant shall:
(1)
Provide a certification of completion from an engineer, architect,
surveyor or other qualified person, verifying that all permanent facilities
have been constructed according to the SWM site plan and report and
approved revisions thereto.
(2)
Provide a set of record drawings.
(3)
Request a final inspection from the Borough to certify compliance
with this chapter, after receipt of the certification of completion
and record drawings by the Borough.
A.
The SWM site plan and report for the project site shall describe
the future operation and maintenance responsibilities. The operation
and maintenance description shall outline required routine maintenance
actions and schedules necessary to ensure proper operation of the
stormwater control facilities.
B.
The SWM site plan and report for the project site shall establish
responsibilities for the continuing operating and maintenance of all
proposed stormwater control facilities, consistent with the following
principles:
(1)
If a development consists of structures or lots that are to be separately
owned and in which streets, sewers, and other public improvements
are to be dedicated to the Borough, stormwater control facilities/BMPs
may also be dedicated to and maintained by the Borough.
(2)
If a development site is to be maintained in a single ownership or
if sewers and other public improvements are to be privately owned
and maintained, then the ownership and maintenance of stormwater control
facilities/BMPs shall be the responsibility of the owner or private
management entity.
(3)
Facilities, areas, or structures used as stormwater BMPs shall be
enumerated as permanent real estate appurtenances and recorded as
deed restrictions or easements that run with the land.
(4)
The SWM site plan and report shall be recorded as a restrictive deed
covenant that runs with the land.
(5)
The Borough may take enforcement actions against an applicant for
failure to satisfy any provision of this chapter.
C.
The Borough, upon recommendation of the Municipal Engineer, shall
make the final determination on the continuing maintenance responsibilities
prior to final approval of the SWM site plan and report. The Borough
may require a dedication of such facilities as part of the requirements
for approval of the SWM site plan. Such a requirement is not an indication
that the Borough will accept the facilities. The Borough reserves
the right to accept or reject the ownership and operating responsibility
for any portion of the stormwater management controls.
D.
If the Borough accepts ownership of stormwater BMPs, the Borough
may, at its discretion, require a fee from the applicant to the Borough
to offset the future cost of inspections, operations, and maintenance.
E.
It shall be unlawful to alter or remove any permanent stormwater
BMP required by an approved SWM site plan or to allow the property
to remain in a condition which does not conform to an approved SWM
site plan, unless the Borough grants an exception in writing.
A.
Prior to final approval of the SWM site plan and report, the applicant
shall sign the operation and maintenance (O&M) agreement in form
and substance approved by the Borough Solicitor covering all stormwater
control facilities that are to be privately owned. The operation and
maintenance (O&M) agreement shall be recorded with the SWM site
plan and made a part hereto.
B.
Other items may be included in the operation and maintenance (O&M)
agreement where determined necessary to guarantee the satisfactory
operation and maintenance of all BMP facilities.
C.
The owner is responsible for operation and maintenance of the stormwater
BMPs. If the owner fails to adhere to the operation and maintenance
(O&M) agreement, the Borough may perform the services required
and charge the owner appropriate fees. Nonpayment of fees may result
in a lien against the property.
A.
PADEP or its designees normally ensure compliance with any permits
issued, including those for stormwater management. In addition to
PADEP compliance programs, the Borough or its designee may inspect
all phases of the installation of temporary or permanent stormwater
management facilities.
B.
During any stage of earth disturbance activities, if the Borough
determines that the stormwater management facilities are not being
installed in accordance with the approved SWM site plan, the Borough
shall revoke any existing permits or approvals until a revised SWM
site plan is submitted and approved as specified in this chapter.
C.
Stormwater BMPs shall be inspected by the landowner, or the landowner's
designee, according to the inspection schedule described on the SWM
site plan for each BMP.
(1)
The Borough may require copies of the inspection reports, in a form
as stipulated by the Borough.
(2)
If such inspections are not conducted or inspection reports not submitted
as scheduled, the Borough, or its designee, may conduct such inspections
and charge the owner appropriate fees. Nonpayment of fees may result
in a lien against the property.
(a)
Prior to conducting such inspections, the Borough shall inform
the owner of its intent to conduct such inspections. The owner shall
be given 30 days to conduct required inspections and submit the required
inspection reports to the Borough.
A.
Upon presentation of proper credentials, duly authorized representatives
of the Borough may enter at reasonable times upon any property within
the Borough to inspect the implementation, condition, or operations
and maintenance of the stormwater BMPs in regard to any aspect governed
by this chapter.
B.
Stormwater BMP owners and operators shall allow persons working on
behalf of the Borough ready access to all parts of the premises for
the purposes of determining compliance with this chapter.
C.
Persons working on behalf of the Borough shall have the right to
temporarily locate on any stormwater BMP in the Borough such devices
as are necessary to conduct monitoring and/or sampling of the discharges
from such stormwater BMP.
D.
Unreasonable delay in allowing the Borough access to a stormwater
BMP is a violation of this chapter.
A.
In the event that a person fails to comply with the requirements
of this chapter, an approved SWM site plan, or fails to conform to
the requirements of any permit or approval issued hereunder, the Borough
shall provide written notification of the violation. Such notification
shall set forth the nature of the violation(s) and establish a time
limit for correction of these violation(s).
B.
Failure to comply within the time specified shall subject such person
to the penalties provisions of this chapter. All such penalties shall
be deemed cumulative and shall not prevent the Borough from pursuing
any and all other remedies. It shall be the responsibility of the
owner of the real property on which any regulated activity is proposed
to occur, is occurring, or has occurred, to comply with the terms
and conditions of this chapter.
A.
The Borough Council or its designee shall enforce all of the provisions
of this chapter. The approved SWM site plan shall be on file at the
project site throughout the duration of the construction activity.
The Borough or its designee may make periodic inspections during construction.
B.
Adherence to approved SWM site plan.
(1)
It shall be unlawful for any person, firm, or corporation to undertake
any regulated activity on any property except as provided for by an
approved SWM site plan and pursuant to the requirements of this chapter.
(2)
It shall be unlawful to alter or remove any control structure required
by the SWM site plan pursuant to this chapter.
(3)
It shall be unlawful to allow a property to remain in a condition
that does not conform to an approved SWM site plan.
A.
Any approval or permit issued by the Borough may be suspended or
revoked for:
(1)
Noncompliance with or failure to implement any provision of the approved
SWM site plan or operation and maintenance (O&M) agreement.
(2)
A violation of any provision of this chapter or any other applicable
law, ordinance, rule or regulation relating to the regulated activity.
(3)
The creation of any condition or the commission of any act during
the regulated activity which constitutes or creates a hazard or nuisance,
pollution, or which endangers the life or property of others.
C.
An approval that has been revoked by the Borough cannot be reinstated.
The applicant may apply for a new approval under the provisions of
this chapter.
Any person aggrieved by any action of the Borough or the Code
Enforcement Officer regarding provisions of this chapter may appeal
in accordance with the provisions of the Municipalities Planning Code,
53 P.S. §§ 10909.1 and 11002-A, within 30 days of the
action.
A.
Any drain (including indoor drains and sinks) or conveyance, whether
on the surface or underground, that allows any nonstormwater discharge
including sewage, process wastewater, and wash water to enter the
Borough's separate storm sewer system or waters of the commonwealth
is prohibited.
B.
Any drain or conveyance connected from a commercial or industrial
land use to the Borough's separate storm sewer system which has
not been documented in plans, maps, or equivalent records and approved
by the Borough is prohibited.
C.
No person shall allow, or cause to allow, discharges into the Borough's separate storm sewer system or into surface waters of the commonwealth which are not composed entirely of stormwater, except as provided in Subsection D below and discharges allowed under a state or federal permit.
D.
The following discharges are authorized unless they are determined
to be significant contributors to pollution to the waters of the commonwealth:
(1)
Discharges from firefighting activities.
(2)
Potable water sources, including dechlorinated waterline and fire
hydrant flushings.
(3)
Irrigation drainage.
(4)
Air-conditioning condensate.
(5)
Springs.
(6)
Water from crawl space pumps.
(7)
Pavement wash waters where spills or leaks of toxic or hazardous
materials have not occurred (unless all spill material has been removed)
and where detergents are not used.
(8)
Flows from riparian habitats and wetlands.
(9)
Uncontaminated water from foundations or from footing drains.
(10)
Lawn watering.
(11)
Dechlorinated swimming pool discharges.
(12)
Uncontaminated groundwater.
(13)
Water from individual residential car washing.
(14)
Routine external building washdown (which does not use detergents
or other compounds).
E.
In the event that the Borough or PADEP determines that any of the discharges identified in Subsection D significantly contribute to pollution of waters of the commonwealth, or is so notified by PADEP, the Borough will notify the responsible person(s) to cease the discharge.
F.
Upon notice provided by the Borough or PADEP under Subsection E, the discharger will have a reasonable time, as determined by the Borough or PADEP, to cease the discharge, consistent with the degree of pollution caused by the discharge.
G.
Nothing in this section shall affect a discharger's responsibilities
under commonwealth law.
Roof drains and sump pumps shall discharge to infiltration areas,
vegetative BMPs, or pervious areas to the maximum extent practicable.
A.
No person shall modify, remove, fill, landscape, or alter any existing
stormwater BMP, facilities, areas, or structures, unless it is part
of an approved maintenance program, without the written approval of
the Borough.
A.
Review and inspection fees for stormwater management site plans and
reports, waiver requests, and compliance, construction or maintenance
inspections shall be established by resolution of Borough Council
to cover costs incurred by the Borough Solicitor and the Borough Engineer
or other professional hired for review or inspection as deemed necessary
by the Borough in order to comply with this chapter.
B.
Application fees for stormwater management site plans and reports
or waiver requests shall include administrative and clerical costs
and a completeness review by the Borough Engineer.
A.
The owner of any land upon which permanent BMPs will be placed, constructed,
or implemented, as described in the SWM site plan, shall record the
following documents in the office of the Recorder of Deeds of Butler
County within 60 days of approval of the SWM site plan by the Borough:
