[Ord. 98-3, 2/25/1998; as amended by Ord. 2005-06, 3/22/2005; by Ord. No. 2019-03, 7/23/2019; and by Ord.
No. 2022-03, 10/25/2022]
The removal of the surface of the land through the combined
action of human activities 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 including tillage, land clearing,
plowing, disking, harrowing, planting, harvesting crops or pasturing
and raising of livestock and installation of conservation measures.
Construction of new building or impervious area is not considered
an agricultural activity.
A landowner, developer, or other person who has filed an
application to the Township for approval to engage in any regulated
activity at a project site in the Township.
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 Part. Stormwater BMPs are
commonly grouped into one of two broad categories or measures: "structural"
or "nonstructural." In this Part, nonstructural BMPs or measures refer
to operational and/or behavior-related practices that attempt to minimize
the contact of pollutants with stormwater runoff, whereas structural
BMPs or measures are those 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.
Documentation, included as part of a drainage plan, detailing
the proposed BMPs, how they will be operated and maintained and who
will be responsible.
Densely vegetated, depressed features that store stormwater
and filter it through vegetation, mulch, planting soil, etc. Ultimately
stormwater is evapotranspirated, infiltrated or discharged. Optimal
bioretention areas mimic natural forest ecosystems in terms of species
diversity, density, distribution, use of native plants, etc.
The Board of Supervisors (BOS) of the Township of Allen,
Northampton County.
STREAMSIDE BUFFERA zone of variable width located along a stream that is vegetated and is designed to filter pollutants from runoff.
SPECIAL GEOLOGIC FEATURE BUFFERA required isolation distance from a special geologic feature to a proposed BMP needed to reduce the risk of sinkhole formation due to stormwater management activities.
Stormwater management techniques such as cisterns and rain
barrels which direct runoff into storage devices, surface or subsurface,
for later reuse, such as for irrigation of gardens and other planted
areas. Because this stormwater is utilized and no pollutant discharge
results, water quality performance is superior to other noninfiltration
BMPs.
Rock consisting chiefly of carbonate minerals, such as limestone
and dolomite; specifically a sedimentary rock composed of more than
50% by weight of carbonate minerals that underlies soil or other unconsolidated,
superficial material.
An underground reservoir or tank for storing rainwater.
A distinctive bowl-shaped depression in the land surface.
It is characterized by internal drainage, varying magnitude and an
unbroken ground surface.
The Northampton County Conservation District.
Constructed wetlands are similar to wet ponds (see below)
and consist of a basin which provides for necessary stormwater storage
as well as a permanent pool or water level, planted with wetland vegetation.
To be successful, constructed wetlands must have adequate natural
hydrology (both runoff inputs as well as soils and water table which
allow for maintenance of a permanent pool of water). In these cases,
the permanent pool must be designed carefully, usually with shallow
edge benches, so that water levels are appropriate to support carefully
selected wetland vegetation.
A pipe, conduit or similar structure, including appurtenant
works, which carries surface water.
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 Pennsylvania Department of Environmental Protection (formerly
the Pennsylvania Department of Environmental Resources).
The depth and time distribution of precipitation from a storm
event measured in probability of occurrence (e.g., fifty-year storm)
and duration (e.g., twenty-four-hour), and used in computing stormwater
management control systems.
A basin designed to retard stormwater runoff by temporarily
storing the runoff and releasing it at a predetermined rate.
The volume of runoff that is captured and released into the
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 as defined in § 8-203 of this Part.
The specific tract of land for which a regulated activity
is proposed.
See "sheet flow."
A right granted by a landowner to a grantee, allowing the
use of private land for stormwater management purposes.
The documentation of the proposed stormwater quantity and quality management controls to be used for a given development site, including a BMP operations and maintenance plan, the contents of which are established in § 8-232.
A construction or other human activity which disturbs the
surface of the land, including, but not limited to, clearing and grubbing,
grading, excavations, embankments, road maintenance, building construction
and the moving, depositing, stockpiling or storing of soil, rock or
earth materials.
The removal of soil particles by the action of water, wind,
ice, or other geological agents.
The dominant land cover during the five-year period immediately
preceding a proposed regulated activity.
Those uses actually attained in the water body on or after
November 28, 1975, whether or not they are included in the water quality
standards. (25 Pa. Code § 93.1)
Federal Emergency Management Agency.
Man-made deposits of natural soils or rock products and waste
materials.
See "vegetated buffers."
Any land area susceptible to inundation by water from any
natural source or delineated by applicable FEMA maps and studies as
being a special flood hazard area. Also includes areas that comprise
Group 13 Soils, as listed in Appendix A of the Pennsylvania DEP Technical
Manual for Sewage Enforcement Officers (as amended or replaced from
time to time by DEP).
The channel of the watercourse and those portions of the
adjoining floodplains that are reasonably required to carry and discharge
the 100-year 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 100-year floodway, it is assumed, absent evidence
to the contrary, that the floodway extends from the stream to 50 feet
from the top of the bank of the stream.
Planning and activities necessary for the management of forestland.
These include conducting a timber inventory, preparation of forest
management plans, silvicultural treatment, cutting budgets, logging
road design and construction, timber harvesting, site preparation,
and reforestation.
The incremental depth of a stormwater management structure,
provided as a safety factor of design, above that required to control
or convey the design runoff event.
Systems and practices that use or mimic natural processes
to infiltrate, evapotranspire, or reuse stormwater on the site where
it is generated.
Replenishment of existing natural underground water supplies.
A written request for a waiver alleging that the provisions
of this Part inflict unnecessary hardship upon the applicant. Waivers
from the water quality provisions of this Part shall not be granted.
Infiltration rates of soils vary widely and are affected
by subsurface permeability as well as surface intake rates. Soils
are classified into four HSGs (A, B, C, and D) according to their
minimum infiltration rate, which is obtained for bare soil after prolonged
wetting. The NRCS 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 the development site may be identified from
a soil survey report that can be obtained from local NRCS offices
or conservation district offices. Soils become less pervious as the
HSG varies from A to D (NRCS).
A surface which prevents the percolation of water into the
ground. Impervious surfaces (or areas) shall include, but not be limited
to, roofs; additional indoor living spaces, patios, garages, storage
sheds and similar structures; and any new streets or sidewalks. Decks,
parking areas, and driveway areas are not counted as impervious areas
if they do not prevent infiltration.
A practice designed to direct runoff into the ground, e.g.,
french drain, seepage pit, seepage trench or bioretention area.
A structure designed to direct runoff into the ground, e.g.,
french drain, seepage pit or seepage trench.
A type of topography or landscape characterized by depressions,
sinkholes, limestone towers and steep-sided hills, underground drainage
and caves. Karst is usually formed on carbonate rocks, such as limestones
or dolomites and sometimes gypsum.
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; a subdivision of
land.
Any natural channel or man-made conveyance system which has
the purpose of transporting runoff from the site to the mainstem.
Site design approaches and small-scale stormwater management
practices that promote the use of natural systems for infiltration,
evapotranspiration, and reuse of rainwater. LID can be applied to
new development, urban retrofits, and revitalization projects. LID
utilizes design techniques that infiltrate, filter, evaporate, and
store runoff close to its source. Rather than rely on costly large-scale
conveyance and treatment systems, LID addresses stormwater through
a variety of small, cost-effective landscape features located on-site.
Any stream segment or other conveyance in a Single Release
Rate, Dual Release Rate or Conditional No Detention I subarea used
as a reach in any DEP approved Act 167 study area hydrologic model.
In Conditional No Detention II subareas the main channel is the Lehigh
River.
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.
A site design practice in which careful limits are placed
on site clearance prior to development allowing for maximum retention
of existing vegetation (woodlands and other), minimum disturbance
and compaction of existing soil mantle and minimum site application
of chemicals post-development. Typically, MD/MM includes disturbance
setback criteria from buildings as well as related site improvements
such as walkways, driveways, roadways and any other improvements.
These criteria may vary by community context as well as by type of
development being proposed. Additionally, MD/MM also shall include
provisions (e.g., deed restrictions, conservation easements) to protect
these areas from future disturbance and from application of fertilizers,
pesticides and herbicides.
The option of using a less-restrictive runoff quantity control
if it can be shown that adequate and safe runoff conveyance exists
and that the less-restrictive control would not adversely affect health,
safety and property.
National Pollutant Discharge Elimination System.
Natural Resource Conservation Service, United States Department
of Agriculture. (Formerly the Soil Conservation Service.)
A structural mechanism designed to remove free oil and grease
(and possibly solids) from stormwater runoff.
"Point source" as described in 40 CFR 122.2 at the point
where the Township's storm sewer system discharges to surface
waters of the commonwealth.
The maximum rate of flow of storm runoff at a given point
and time resulting from a specified storm event.
The computer-based hydrologic modeling technique used in
previous Act 167 Plans. PSRM was also updated to include water quality
modeling capabilities and renamed PSRM-QUAL. The PSRM and PSRM-QUAL
calculation methodologies were used as the basis for writing the watershed
model.
An individual, partnership, public or private association
or corporation, or a governmental unit, public utility or other for-
or not-for-profit statutory entity or other legal entity whatsoever
which is recognized by law as the subject of rights and duties.
Any area not defined as impervious.
Any discernible, confined and 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 § 92.1.[1]
The determination of the depth to bedrock, the depth to the
seasonal high water table and the soil permeability for a possible
infiltration location on a site through the use of published data
and on-site surveys. In carbonate bedrock areas, the location of special
geologic features must also be determined along with the associated
buffer distance to the possible infiltration area. See Appendix G.[2]
The specific area of land where any regulated activities
in the Township are planned, conducted, or maintained.
A person who owns or operates a public water system.
A system which provides water to the public for human consumption
which has at least 15 service connections or regularly serves an average
of at least 25 individuals daily at least 60 days out of the year.
(See 25 Pa. Code Chapter 109.)
A licensed professional geologist or a licensed professional
engineer who has a background or expertise in geology or hydrogeology.
A method of peak runoff calculation using a standardized
runoff coefficient (Rational "c"), acreage of tract and rainfall intensity
determined by return period and by the time necessary for the entire
tract to contribute runoff. The Rational formula is stated as follows:
Q = ciA, where "Q" is the calculated peak flow rate in cubic feet
per second, "c" is the dimension less runoff coefficient (see Appendix
C[3]), "i" is the rainfall intensity in inches per hour, and
"A" is the area of the tract in acres.
Any natural or man-made runoff conveyance channels used for
modeling purposes to connect subareas and transport flows downstream.
Actions or proposed actions which impact upon proper management of stormwater runoff and which are governed by this Part as specified in § 8-203.
Earth disturbance activity other than agricultural plowing
or tilling of one acre or more with a point source discharge to surface
waters or to the Township's storm sewer system or earth disturbance
activity of five acres or more regardless of the planned runoff. This
includes earth disturbance on any portion of, part or during any stage
of a larger common plan of development.
The percentage of the predevelopment peak rate of runoff
for a development site to which the post-development peak rate of
runoff must be controlled to avoid peak flow increases throughout
the watershed.
The volume of of runoff that is captured and not released
directly into the surface water of this commonwealth during or after
a storm event.
The average interval in years over which an event of a given
magnitude can be expected to recur. For example, the twenty-five-year
return period rainfall or runoff event would be expected to recur
on the average once every 25 years.
Earth disturbance activities within the existing road cross-section
such as grading and repairing existing unpaved road surfaces, cutting
road banks, cleaning or clearing drainage ditches and other similar
activities.
That part of precipitation which flows over the land.
The former Soil Conservation Service, U.S. Department of
Agriculture, now known as the "NRCS."
Soils or other materials transported by surface water as
a product of erosion.
A chamber which provides storage below the outlet in a storm
inlet to collect sediment, debris and associated pollutants, typically
requiring periodic cleanout.
An area of excavated earth filled with loose stone or similar
material and 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.
Stormwater runoff flowing in a thin layer over the ground
surface.
A method of runoff computation developed by NRCS which is
based upon relating soil type and land use/cover to a runoff parameter
called a curve number.
Carbonate bedrock features, including but not limited to
closed depressions, existing sinkholes, fracture traces, lineaments,
joints, faults, caves and pinnacles, which may exist and must be identified
on a site when stormwater management BMPs are being considered.
A program that identifies procedures for preventing and,
as needed, cleaning up potential spills and makes such procedures
known and the necessary equipment available to appropriate personnel.
As defined under state regulations, protection of designated
and existing uses (see 25 Pa. Code Chapters 93 and 96), including:
Each stream segment in Pennsylvania has a designated use, such
as "cold water fishes" or "potable water supply," which are listed
in Chapter 93. These uses must be protected and maintained, under
state regulations.
Existing uses are those attained as of November 1975, regardless
of whether they have been designated in Chapter 93. Regulated earth
disturbance activities must be designed to protect and maintain existing
uses and maintain the level of water quality necessary to protect
those uses in all streams and to protect and maintain water quality
in special protection streams.
Water quality involves the chemical, biological and physical
characteristics of surface water bodies. After regulated earth disturbance
activities are complete, these characteristics can be impacted by
addition of pollutants such as sediment, and changes in habitat through
increased flow volumes and/or rates as a result of changes in land
surface area from those activities. Therefore, permanent discharges
to surface waters must be managed to protect the stream bank, streambed
and structural integrity of the waterway, to prevent these impacts.
A method of routing or moving an inflow hydrograph through
a reservoir or detention structure. The method solves the mass conservation
equation to determine an outflow hydrograph as it leaves the storage
facility.
Areas which lack adequate stormwater collection and/or conveyance
facilities and which present a hazard to persons or property. These
areas are either documented in Appendix B[4] of this Part or identified by the Township or Township
Engineer.
A system of pipes or other conduits which carries intercepted
surface runoff, street water and other wash waters, or drainage, but
excludes domestic sewage and industrial wastes.
The surface runoff generated by precipitation reaching the
ground surface.
Any number of structural mechanisms such as multi-chamber
catch basins, sand/peat filters, sand filters and so forth which are
installed to intercept stormwater flow and remove pollutants prior
to discharge. Typically, these systems require periodic maintenance
and cleanout.
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.
Any plan for managing stormwater runoff adopted by Northampton
County for a watershed as required by the Act of October 4, 1978,
P.L. 864 (Act 167), and known as the "Storm Water Management Act."
A watercourse.
The smallest unit of watershed breakdown for hydrologic modeling
purposes for which the runoff control criteria have been established
in the stormwater management plan.
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.
Any and all rivers, streams, creeks, rivulets, impoundments,
ditches, watercourses, storm sewers, lakes, dammed water, wetlands,
ponds, springs and all other bodies or channels of conveyance of surface
water, or parts thereof, whether natural or artificial, within or
on the boundaries of this commonwealth.
A low-lying stretch of land which gathers or carries surface
water runoff.
The report written by Cahill Associates that addresses the
feasibility of infiltration in carbonate bedrock areas in the Little
Lehigh Creek Watershed. The report is available at the LVPC offices.
Allen Township, Northampton County, Pennsylvania.
Racks, screens or other similar devices installed in a storm
drainage system to capture coarse pollutants (trash, leaves, etc.).
United States Department of Agriculture.
Gently sloping areas that convey stormwater as sheet flow
over a broad, densely vegetated earthen area, possibly coupled with
the use of level spreading devices. Vegetated buffers should be situated
on minimally disturbed soils, have low-flow velocities and extended
residence times.
Vegetated systems installed on roofs that generally consist
of a waterproof layer, a root-barrier, drainage layer (optional),
growth media, and suitable vegetation. Vegetated roofs store and eventually
evapotranspirate the collected rooftop rainfall; overflows may be
provided for larger storms.
Broad, shallow, densely vegetated, earthen channels designed
to treat stormwater while slowly infiltrating, evapotranspirating,
and conveying it. Swales should be gently sloping with low flow velocities
to prevent erosion. Check dams may be added to enhance performance.
Any number of commercially available devices that are inserted
into storm inlets to capture sediment, oil, grease, metals, trash,
debris, etc.
Any channel of conveyance of surface water having defined
bed and banks, whether natural or artificial, with perennial or intermittent
flow.
Any and all rivers, streams, creeks, rivulets, impoundments,
ditches, watercourses, storm sewers, lakes, dammed water, wetlands,
ponds, springs, and all other bodies or channels of conveyance of
surface and underground water, or parts thereof, whether natural or
artificial, within or on the boundaries of this commonwealth.
The computer-based hydrologic modeling technique adapted
to the Little Lehigh Creek Watershed for the Act 167 Plan. This model
was written by Tarsi Software Laboratories and uses the same algorithms
found in the Penn State Runoff Quality Model (PSRM-QUAL). The model
has been calibrated to reflect actual flow values by adjusting key
model input parameters.
The entire region or area drained by a river or other body
of water, whether natural or artificial.
A basin that provides for necessary stormwater storage as
well as a permanent pool of water. To be successful, wet ponds must
have adequate natural hydrology (both runoff inputs as well as soils
and water table which allow for maintenance of a permanent pool of
water) and must be able to support a healthy aquatic community so
as to avoid creation of mosquito and other health and nuisance problems.
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.
[1]
Editor's Note: Former Title 25, Chapter 92, of the Pennsylvania
Code was reserved October 9, 2010. See now 25 Pa. Code § 92a.1
et seq.
[2]
Editor's Note: Appendix G is included as an attachment to this chapter.
[3]
Editor's Note: Appendix C is included as an attachment to this chapter.
[4]
Editor's Note: Appendix B is included as an attachment to this chapter.
