For the purposes of this chapter, certain terms
and words used herein shall be interpreted as follows:
A.
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.
B.
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.
C.
The words "shall" and "must" are mandatory; the words
"may" and "should" are permissive.
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 activities and natural processes, at a rate greater
than would occur because of the natural processes alone.
Activities, facilities, measures or procedures used to manage stormwater quantity and quality impacts from the regulated activities listed in § 507-5, to meet state water quality requirements, to promote groundwater recharge and to otherwise meet the purposes of this chapter.
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.
STREAM-SIDE 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.
The City of Easton, Northampton County, Pennsylvania.
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, as applicable.
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.
The depth and time distribution of precipitation from a storm
event measured in probability of occurrence (e.g., one-hundred-year
storm) and duration (e.g., 24 hours) and used in computing stormwater
management control systems.
A basin designed to retard stormwater runoff by temporarily
storing the runoff and releasing it at the appropriate release 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.
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 § 507-20.
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.
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 Chapter 93.1)
Man-made deposits of natural soils or rock products and waste
materials.
See "vegetated buffers."
The incremental depth in a stormwater management structure,
provided as a safety factor of design, above that required to convey
the design runoff event.
Replenishment of existing natural underground water supplies.
A written request for a waiver alleging that the provisions
of this chapter inflict unnecessary hardship upon the applicant. A
hardship waiver does not apply to and is not available from the water
quality provisions of this chapter and should not be granted.
Soils are classified into four HSGs (A, B, C and D) to indicate
the minimum infiltration rates, which are obtained for bare soil after
prolonged wetting. The Natural Resources Conservation Service (NRCS)
of the U.S. 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 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 permeable as the HSG varies from A to D.
A land use or activity that generates higher concentrations of hydrocarbons, trace metals or other toxic substances than typically found in stormwater runoff. These land uses are listed in § 507-14P.
A surface which prevents the percolation of water into the
ground.
A practice designed to direct runoff into the ground, e.g.,
french drain, seepage pit, seepage trench or bioretention area.
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 ratio of the land area draining to the system, as modified by the weighting factors in § 507-17B., compared to the base area of the infiltration system.
A development approach that promotes practices that will
minimize post-development runoff rates and volumes thereby minimizing
needs for artificial conveyance and storage facilities. Site design
practices include preserving natural drainage features, minimizing
impervious surface area, reducing the hydraulic connectivity of impervious
surfaces and protecting natural depression storage.
Any natural channel or man-made conveyance system which has
the purpose of transporting runoff from the site to the mainstem.
Any stream segment or other conveyance used as a reach in
the regulated watershed hydrologic model.
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 stormwater design manual written by the Maryland Department
of the Environment and the Center for Watershed Protection. As of
January 2004, the Manual can be obtained through the following website:
www.mde.state.md.us.
Site design practices 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.
City of Easton, Northampton County, Pennsylvania.
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 Resources Conservation Service, U.S. 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 municipality's storm sewer system discharges to surface
waters of the commonwealth.
The maximum rate of flow of stormwater runoff at a given
location and time resulting from a specified storm event.
The computer-based hydrologic modeling technique adapted
to each watershed for the Act 167 plans. The model was "calibrated"
to reflect actual flow values by adjusting key model input parameters.
An individual, partnership, public or private association
or corporation, firm, trust, estate, municipality, governmental unit,
public utility or any other legal entity whatsoever which is recognized
by law as the subject of rights and duties.
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.
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 E.[1]
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 Method formula is stated
as follows: Q = ciA, where "Q" is the calculated peak flow rate in
cubic feet per second, "c" is the dimensionless runoff coefficient
(see Appendix A[2]), "i" is the rainfall intensity in inches per hour, and
"A" is the area of the tract in acres.
Any of the natural or man-made runoff conveyance channels
used for watershed runoff modeling purposes to connect the subareas
and transport flows downstream.
The portion of the water quality volume (WQv) used to maintain groundwater recharge rates at development sites. (See § 507-14J.)
Actions or proposed actions which impact upon proper management of stormwater runoff and which are governed by this chapter as specified in § 507-5.
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 municipality'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 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 of 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.
Chambers which provide 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, pinnacles and geologic contacts between carbonate
and noncarbonate bedrock, 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
is listed in Chapter 93. These uses must be protected and maintained,
under state regulations.
"Existing uses" are those attained as of November
1975, regardless 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 streambank, 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 the "Description of Storm Drainage Problem Areas" at the end of this chapter or identified by the municipality or Municipal 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.
The plan for managing stormwater runoff adopted by Northampton
County for the regulated watersheds as required by the Act of October
4, 1978, P.L. 864, (Act 167), as amended, and known as the "Stormwater
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.
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. See also "vegetated swale."
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 Lehigh Valley
Planning Commission offices.
Racks, screens or other similar devices installed in a storm
drainage system to capture coarse pollutants (trash, leaves, etc.).
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.
Vegetated earthen channels designed to convey
stormwater. These swales are not considered to be water quality BMPs.
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 channel of conveyance of surface water having defined
bed and banks, whether natural or artificial, with perennial or intermittent
flow.
Any number of commercially available devices that are inserted
into storm inlets to capture sediment, oil, grease, metals, trash,
debris, etc.
The volume needed to capture and treat 90% of the average annual rainfall volume. (See § 507-14B.)
The entire region or area drained by a river or other body
of water, whether natural or artificial.
Basins that provide 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.
[1]
Editor's Note: Appendix E is included at the end of this chapter.
[2]
Editor's Note: Appendix A is included at the end of this chapter.
