A.
For all regulated activities, SWM facilities shall be designed, implemented,
operated, and maintained to meet the purposes and requirements of
this ordinance and to meet all requirements under Title 25 of the
Pennsylvania Code, the Clean Streams Law,[1] and the Storm Water Management Act.[2] Various SWM BMPs and their design standards are listed
in the Pennsylvania Stormwater Best Management Practices Manual (BMP
Manual3), as amended and updated, which
shall be followed unless otherwise noted within this or other ordinances
or regulations of the municipality. Deviations from these specifications
and standards shall only be allowed by specific written request to
and explicit approval of the Municipal Engineer.
B.
For all regulated activities, ESC facilities 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 ordinance and to meet all requirements under Title 25 of the
Pennsylvania Code and the Clean Streams Law. Various ESS BMPs and
their design standards are listed in the Erosion and Sediment Pollution
Control Program Manual (E&S Manual), as amended and updated, which
shall be followed unless otherwise noted within this or other ordinances
or regulations of the municipality. Deviations from these specifications
and standards shall only be allowed by specific written request to
and explicit approval of the Municipal Engineer.
C.
For all regulated activities, improvements shall be designed and
constructed in accordance with PennDOT's Publications 408 and
72M, as amended and updated, unless otherwise noted within this or
other ordinances or regulations of the municipality. If design or
construction conflicts arise between Publications 408/72M and PADEP
regulations, such as the BMP and E&S Manual, the PADEP regulations
shall preside. Deviations from these specifications and standards
shall only be allowed by specific written request to and explicit
approval of the Municipal Engineer.
E.
Corrugated metal pipe shall not be used for any purpose within the
municipality.
F.
All regulated activities shall include such measures as necessary
to:
1.
Protect health, safety, and property.
2.
Meet the water quality goals of this ordinance by implementing measures
to:
a.
Minimize disturbance to floodplains, wetlands, and wooded areas.
b.
Maintain or extend riparian buffers.
c.
Avoid erosive flow conditions in natural flow pathways.
d.
Minimize thermal impacts to waters of this commonwealth.
e.
Disconnect impervious surfaces by directing runoff to pervious
areas, wherever possible.
f.
Prevent pollution of stormwater runoff by ceasing activities
that clearly contaminate runoff.
3.
Incorporate the techniques for low-impact development practices described
in the BMP Manual.
G.
For all regulated activities, unless preparation of a SWM site plan and report is specifically exempted in § 158-302:
H.
SWM site plans approved by the municipality shall be on site throughout
the duration of the regulated activity.
I.
Impervious areas:
J.
Stormwater flows may not be transferred from one watershed listed
within an approved Act 167 stormwater management plan to another.
K.
Stormwater flows onto adjacent property shall not be created, increased,
relocated, significantly concentrated, or otherwise detrimentally
altered without written approval from the affected property owner(s).
Such stormwater flows shall be subject to the requirements of this
ordinance.
L.
No stormwater or other related discharges shall discharge directly
into a public right-of-way or onto paved surfaces intended for vehicular
or pedestrian travel (including but not limited to parking lots, public
or private streets, sidewalks, shared driveways, etc.). "Directly,"
for the purpose of this ordinance, will vary depending on site conditions,
the concentration and volume of the discharge, and intermediary surfaces,
but in no case shall a discharge directed to the above areas be closer
than 15 feet.
M.
All regulated activities shall limit surface water runoff or stormwater
discharges into areas of karst geology or where karst features are
observed.
N.
All stormwater discharges with pipe sizes greater than or equal to
12 inches shall be provided with either reinforced concrete endwalls
or plastic end sections and shall also include outlet protection consistent
with the E&S Manual.
O.
For regulated activities involving the subdivision and/or land development
of five or more lots or structures, communal SWM and conveyance facilities
with a single entity responsible for operation and maintenance of
all facilities shall be utilized. Stormwater management may not be
accomplished by utilizing SWM facilities individually designed for
and placed within or on each lot or structure, and the operation and
maintenance of facilities shall not be delegated to individual lot
owners, tenants, or other multiples of entities within the project.
P.
For regulated activities involving the subdivision and/or land development
of five or more lots or structures, subterranean SWM facilities (such
as, but not limited to, infiltration pits, beds, or trenches) are
prohibited. Amended soils and similar items incidental to the construction
of aboveground SWM facilities are not included in this prohibition.
Q.
For regulated activities proposing earth disturbances of greater
than or equal to 5,000 square feet, submission of an erosion and sediment
control plan to the county conservation district/reviewing authority
for adequacy review shall be required at the sole discretion of the
Municipal Engineer. Subsequent evidence of approval shall also be
required.
R.
For regulated activities proposing earth disturbances of greater
than or equal to 43,560 square feet, submission of an erosion and
sediment control plan to the county conservation district/reviewing
authority for NPDES permit approval shall be required. Subsequent
evidence of approval shall also be required.
S.
Any regulated activities within an existing, known stormwater management
problem area, or having the potential to negatively impact an existing,
known stormwater management problem area, may be required by the municipality
to include additional, reasonable measures beyond those listed within
this ordinance in order to ensure that any effects of the regulated
activity do not exacerbate or further contribute to the issues affecting
said problem area. In no case shall the applicant be required to resolve
the existing, known stormwater management problems beyond the obligations
so listed.
T.
All drainage plans shall take into account and provide for existing
flows within the entire watershed.
U.
All lots shall be laid out and graded to prevent cross lot drainage
and to provide positive drainage away from proposed building locations
and any primary or alternate septic system location.
V.
An adequate storm sewer system consisting of inlets and other underground
drainage structures with approved outlets shall be constructed where
the runoff of stormwater and the prevention of erosion cannot be accomplished
satisfactorily by surface drainage facilities, as determined by the
Municipal Engineer.
W.
Outlet locations shall be approved by the Municipal Engineer.
X.
Sequence of construction. No substantial grading shall occur and
no building permits shall be issued for any building unless any detention
basin, siltation basin, or improved major swale approved to handle
the resulting runoff is in place. Any detention basin shall be seeded
and stabilized and have an installed outlet structure prior to the
construction of any streets or building within that drainage basin.
Y.
All stormwater management methods are subject to approval by the
Municipal Engineer.
Z.
On-site SWM facilities and conveyance facilities shall be designed
to safely convey off-site flows in accordance with the regulations
of this ordinance. Off-site flows are not required to be attenuated
in volume and peak rate SWM facilities.
AA.
The Municipality, after consultation with Northampton County Conservation
District and/or DEP, may approve measures for meeting the state water
quality and other stormwater runoff requirements other than those
in this ordinance, provided that they meet the minimum requirements
of, and do not conflict with, state law, including but not limited
to the Clean Streams Law.[3]
[3]
Editor's Note: See 35 P.S. § 691.1 et seq.
A.
Regulated activities that result in: the alteration or development of less than 1,000 square feet of land in a manner that may affect stormwater runoff (excluding stormwater BMPs); earth disturbances of less than 5,000 square feet; and/or the cumulative increase of impervious area less than 1,000 square feet from the original date of the passage of this ordinance are exempt from the requirements in Article IV of this ordinance.
D.
Exemptions from any provisions of this ordinance shall not relieve the applicant from the requirements in § 158-301. If any of the requirements in § 158-301 are not met, the municipality at its sole discretion may revoke any exemptions from any provisions of this ordinance without the necessity of any proceedings for revocation, and the applicant may be required by the municipality to cease all activities and/or comply with the provisions of this ordinance.
A.
For all regulated activities requiring a major SWM permit, a riparian
buffer easement shall be created and recorded that encompasses an
existing or potential riparian buffer.
B.
Except as required by Chapter 102, the riparian buffer easement shall be measured to be the greater of the limit of the 100-year floodplain or a minimum of 50 feet from the top of the stream bank (on each side).
C.
When present, provisions for permanent access to riparian buffer
easements shall also be granted to the municipality via a note as
listed in § 158-401a.X.10.
D.
Minimum management requirements for riparian buffers:
1.
Existing native vegetation shall be protected and maintained within
the riparian buffer easement. If no or limited existing native vegetation
is present, additional native vegetation shall be specified and planted
within the riparian buffer easement to create a diverse native plant
community appropriate to the intended ecological context of the site.
2.
Whenever practicable, invasive vegetation shall be actively removed,
and the riparian buffer easement shall be specified and planted with
native trees, shrubs, and other native vegetation in the invasive
vegetation's place to create a diverse native plant community
appropriate to the intended ecological context of the site.
E.
The riparian buffer easement shall be enforceable by the municipality
and shall be recorded in the appropriate County Recorder of Deeds
Office, so that it shall run with the land and shall limit the use
of the property located therein. The easement shall allow for continued
private ownership and shall count toward the minimum lot area as required
by zoning, unless otherwise specified in the Zoning Ordinance.[1]
F.
Any permitted use within the riparian buffer easement shall be conducted
in a manner that will maintain the extent of the existing 100-year
floodplain, improve or maintain the stream stability, leave native
vegetation undisturbed as much as is practicable, and preserve and
protect the ecological function of the floodplain.
G.
Specific prohibitions within riparian
buffer easements:
a.
Septic drainfields and sewage disposal systems.
b.
Livestock grazing and access, except areas specifically necessary
for livestock crossing of waterways.
c.
Mowing is prohibited; exceptions may be granted at the sole discretion
of the Municipal Engineer.
d.
Use of fertilizers, pesticides, and herbicides.
H.
Specific requirements for uses
within riparian buffer easements:
a.
All uses shall comply with the ordinances, provisions, and regulations
of the municipality and any other applicable entities.
b.
All uses shall limit vegetative clearing to the minimum extent necessary
for the execution of the use; general clearing of the riparian buffer
easement is not permitted.
c.
Trails shall be for nonmotorized use only.
d.
Docks, boat ramps, and other similar improvements shall be comprised
of stable, nonerosive material(s).
SWM facilities shall comply with the below standards as applicable
to the proposed facility:
A.
Infiltration facilities shall be required unless subsurface conditions prevent the use of infiltration BMPs, in which case § 158-304B below shall be followed. Infiltration facilities:
1.
Shall be spread out, made as shallow as practicable, and located
to maximize use of natural on-site infiltration features while still
meeting the other requirements of this ordinance.
2.
Must have soil permeability greater than or equal to 0.5 inch/hour
and less than or equal to 12 inches per hour.
3.
Shall be protected from disturbance and compaction.
4.
Shall be set back by the following distances:
a.
For all SWM permits: 100 feet from water supply wells.
b.
For major SWM permits: 15 feet downgradient or 100 feet upgradient
from building foundations.
c.
For minor SWM permits: 15 feet downgradient or 40 feet upgradient
from building foundations.
d.
For major SWM permits: 50 feet from septic system drainfields.
e.
For minor SWM permits: 25 feet from septic system drainfields.
f.
For major SWM permits: if the above neighboring features are
not present, 100 feet from property lines unless evidence is provided
that the above setbacks can be maintained for existing or potential
wells, foundations, and drainfields on neighboring properties.
g.
For major SWM permits: 50 feet from a geologic contact with
carbonate bedrock unless a carbonate assessment report is done and
shows either the absence of special geologic features within 50 feet
of the proposed infiltration area or provides recommendations on the
means of acceptability for infiltration.
5.
Infiltration for stormwater management is encourage where soils and
geology permit, consistent with the provisions or this ordinance and,
where appropriate, the Recommendation Chart for Infiltration Stormwater
Management BMPs in Carbonate Bedrock in Appendix D.[1]
[1]
Editor's Note: Appendix D is included as an attachment to this chapter.
B.
All SWM facilities shall be set back a minimum of 15 feet from a
property line or public right-of-way as measured from the nearest
point of the facility that may provide water storage.
C.
Runoff not being treated by infiltration shall utilize two SWM BMPs
in series ("treatment train"), including but not limited to bioretention
facilities, capture/reuse, constructed wetlands, dry extended detention
ponds, stormwater filters, vegetated buffers/filter strips, vegetated
roofs, vegetated swales, water quality inlets, and/or wet detention
ponds. The second BMP shall be a vegetated buffer, filter strip, bioretention
facility, vegetated swale, or other BMP that provides a thermal benefit
to surface waters.
D.
Low-flow channels are prohibited.
E.
Trash racks shall be provided for all orifices equivalent to 12 inches
or smaller in diameter. Additionally, all basin inflow and outflow
structures shall be designed with trash racks over the outflows where
practicable.
F.
Anti-seep collars shall be provided on all outflow culverts in accordance
with the methodology in the E&S Manual. An increase in seepage
length of 15% must be used in accordance with the requirements for
permanent anti-seep collars.
G.
Embankment/berm tops shall not be planted with vegetation greater
than three feet in mature height. Only vegetation that is tolerant
to the conditions of embankment planting (for example, lack of water
retainage in the soil) may be utilized. When this requirement is in
conflict with other ordinances or regulations (for example, landscape
buffer plantings), this requirement shall preside for the purposes
of public safety and protection.
H.
Embankment/berm side slopes shall be no steeper than 3:1.
I.
Embankment/berm soils shall have low erodibility factors as per the
E&S Manual and be identified on the SWM site plan.
J.
If a major SWM permit is required, all embankments/berms shall meet
Subsection J.1 through 4. If a minor SWM permit is required, embankments/berms
greater than or equal to three feet in height shall:
1.
Have a cross-sectional top width of at least five feet.
2.
Have emergency spillways capable of providing nonerosive release
of the post-development 100-year design storm. The emergency spillway
shall provide a minimum one foot of freeboard below the top of berm
elevation, convey the entire 100-year design storm at a maximum depth
of one foot over the spillway, and may not be utilized as an outflow
for design storms up to and including the 100-year storm.
3.
Have cutoff/key trenches of impervious material.
4.
The primary outflow structure must be designed to pass all design
storms (up to and including the 100-year event) without discharging
through the emergency spillway.
K.
All facilities shall drain 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 unless, at the sole discretion of the Municipal
Engineer, the BMP is specifically designed to function with differing
time frames (for example, wet ponds, constructed wetlands, etc.).
L.
Maximum water depth in any open SWM facility shall be no greater
than six feet when functioning through the primary outlet structure.
M.
The 100-year water surface elevation within any SWM facility shall
provide a minimum of 1.0 foot of freeboard below the invert of the
emergency spillway. For facilities that do not utilize an emergency
spillway, this freeboard shall be provided to the top of the storage
facility (i.e., top of berm, top of stone pit, etc.).
N.
A minimum four-foot-high, galvanized or vinyl-clad chain-link metal
fence, or any material and fence design acceptable to the municipality,
with a self-closing and self-latching gate with a minimum opening
of 10 feet shall be provided around stormwater management facilities
if any of the following conditions are present:
1.
When deemed a public safety hazard at the sole discretion of the
municipality.
2.
The maximum depth of water in the basin after a ten- or twenty-five-year
storm is greater than 30 inches.
3.
The basin is intended to hold water for periods of longer than three
hours after the storm subsides.
4.
The basin is to be dedicated to the municipality.
5.
Fencing of a detention basin may be waived by the municipality upon
the recommendation of the Municipal Engineer if the nearest residential
zoning district, school, existing dwelling or recreation facility
is at least 1,500 feet away in walking distance from the basin.
O.
Floodplains:
1.
Facilities and their points of discharge shall not be located within
the 1% flood event (100-year floodplain) as determined by FEMA, HEC-RAS,
or similar analysis. If no floodplain is defined, the floodplain is
assumed to extend 50 feet from the top of stream bank in both directions.
2.
Facility bottom elevations must be greater than 1% (100-year) floodplain
elevations. If no floodplain is defined, the floodplain is assumed
to extend 50 feet from the top of stream bank in both directions.
3.
Novel approaches to stormwater management that require placement within the floodplain, including but not limited to floodplain restorations, may be exempted from the requirements in § 158-304O.1 and 2 above at the sole discretion of the Municipal Engineer.
4.
Properties that are entirely or majority constrained by floodplains may be exempted from the requirements in § 158-304O.1 and 2 above at the sole discretion of the Municipal Engineer.
Q.
The type, location, and number of landscaping and planting specification
shall be provided for all stormwater management facilities and be
specific for each type of facility.
R.
Stormwater management facilities excavated to carbonate rock must
either be fitted with an impervious clay liner, or if infiltration
is determined to be an acceptable practice, over-excavated four feet
and refilled with a suitable material mix. Suitable backfill material
is subject to approval from the Municipal Engineer.
S.
The minimum circular orifice diameter for controlling discharge rates
from detention facilities shall be three inches.
T.
Aeration devices may be required for retention basins, dependent
upon the quality of influent and retention time.
U.
Within areas containing soils identified by the Soil Conservation
Service to be sinkhole prone, permanent detention basins shall be
lined with a material which after installation attains a maximum permeability
rate as determined by the Township's Geotechnical Engineer or Township
Engineer.
Conveyance facilities shall:
A.
Safely convey the twenty-five-year design storm without erosion or
hazard utilizing Manning's equation.
B.
Be prohibited from connecting to or discharging into existing downstream
conveyance or storage systems, whether man-made or natural, without
verification of the adequacy of downstream hydraulic capacity.
C.
In the case of storm sewers:
1.
Completely contain flows with no surface discharges.
2.
Be constructed with watertight joints. If conveyance facilities are
proposed that require watertight joints, provide a note as listed
in § 158-401a.X.7.
3.
Be designed and constructed without "knocking out" any inlet or structure
corners. If inlets or structures are proposed, provide a note as listed
in § 158-401a.X.8 below.
4.
Have inlets, manholes, or similar structures at all horizontal and/or
vertical directional changes. Tee joints, elbows, wyes, and similar
structures are prohibited. No run of pipe shall exceed 400 feet in
length without appropriate measures to allow cleanout.
5.
Include double inlets set 0.2 foot below the final paving elevation
on both sides of the low point of a curbed street.
6.
Not have inlets placed in front of or within three feet of a driveway.
7.
Not have inlets spaced more than 600 feet apart.
8.
Not have manholes spaced more than 600 feet apart without an inlet
in between.
9.
Have all upstream pipe crown elevations be greater than or equal
to all downstream pipe crown elevations.
10.
Have flow velocities greater than or equal to 2.5 feet per second.
11.
Have slopes greater than or equal to 0.5%.
12.
Have a minimum pipe size of 15 inches in diameter.
13.
Have a minimum two-inch drop between the lowest inlet pipe invert
elevation and the outlet pipe invert elevation within inlets.
14.
All inlets in paved areas shall have heavy-duty bicycle-safe
grating consistent with PennDOT Publication 72M. If inlets or structures
are proposed, provide a note as listed in § 158-401a.X.16
below.
15.
Inlets, junction boxes, or manholes greater than five feet in
depth shall be equipped with ladder rungs and shall be detailed on
the SWM site plan.
16.
Inlets shall not have a sump condition in the bottom unless
designed as a water quality BMP, and shall have flow channels installed.
17.
Provide the note listed in § 158-401a.X.18 stating
concrete top units and grade adjustment rings shall be set in a bed
of full mortar according to Publication 408.
18.
Pavement base drain shall be provided at all low points in cut
areas, toe of slope areas, and other areas dictated by proven engineering
principles and design judgments. All base drains shall be in accordance
with PennDOT Publication 408.
E.
In the case of swales:
F.
In the case of culverts, bridges, and other conveyance facilities
that convey surface drainage across or under streets or other vehicular
passageways (excluding driveways and access drives), whether public
or private:
A.
For modeling purposes of both volume and rate controls:
1.
Design storm values should be obtained from the following sources
depending on methodology:
a.
TR-20/TR-55 precipitation frequency estimates: the latest version
of the Precipitation-Frequency Atlas of the United States6, National Oceanic and Atmospheric Administration
(NOAA), National Weather Service, for the twenty-four-hour storm.
b.
Rational Method design intensity values: the latest version
of PennDOT Publication 5847, Chapter 7A,
Region 4, for the one- through 100-year storm (U.S. Customary).
|
If either source is replaced in full by either entity, the latest
version of the replacement source shall be utilized.
|
2.
Time of concentration (Tc) shall be calculated utilizing the TR-55
segmental method, with a maximum sheet flow length of 100 feet.
a.
The minimum Tc for any watershed or subwatershed shall be five
minutes.
b.
Post-development conditions may assume a five-minute Tc, but
may never be greater than the predevelopment Tc for any watershed
or subwatershed.
c.
Predevelopment Tc values may not be assumed; predevelopment
Tc values must be calculated.
d.
The time of concentration for all conveyance facilities shall
be the minimum Tc of five minutes.
3.
Runoff coefficients and curve numbers are listed within Appendix
B.[1]
[1]
Editor's Note: Appendix B is included as an attachment to this chapter.
4.
Existing (predevelopment) nonforested pervious areas must be considered
meadow in good condition.
5.
Twenty percent of existing impervious area, when present, shall be
considered meadow in good condition in the model for existing conditions.
6.
For regulated activities requiring a major SWM permit due to taking place on sites 1) with greater than or equal to 5,000 square feet of existing impervious area; 2) that are not controlling the runoff from the existing impervious area in a manner consistent with this ordinance; and 3) whose activities do not qualify for the exemptions listed in § 158-302, 50% of existing impervious area, when present, shall be considered meadow in good condition in the model for existing conditions. This requirement replaces the requirement in § 158-306A.5 above.
7.
Meadow may not be used to model proposed (post-development) nonforested
pervious areas unless the area being modeled is specifically designed
to be and designated/delineated on the plan to remain as a bona fide
meadow that may not be removed or altered by the property owner. Specified
native plantings and O&M, including but not limited to routine
weeding of invasive species, should be included on the plan and in
any agreements if this option is chosen.
8.
Other than for calculating dewatering times, dynamic rate and volume
control credits and/or calculations, including but not limited to
infiltration, exfiltration, and evapotranspiration, are not permitted
in the modeling of said controls. Only permanent structural improvements
shall be modeled and/or credited.
9.
Alternative methods of modeling volume and rate controls may be accepted
on a case-by-case basis at the sole discretion of the Municipal Engineer.
B.
Volume controls.
1.
Volume controls shall be required for all regulated activities requiring
a minor or major SWM permit.
2.
Water volume controls shall be implemented using the Design Storm
Method or the Simplified Method:
a.
The Design Storm Method (similar to CG-1 in the BMP Manual)
is applicable to any size of regulated activity. This method requires
detailed modeling based on site conditions.
1.
For regulated activities requiring a minor SWM permit, do not
increase the post-development total runoff volume for all storms equal
to or less than the two-year twenty-four-hour duration precipitation
plus 20%.
2.
For regulated activities requiring a major SWM permit, do not
increase the post-development total runoff volume for all storms equal
to or less than the two-year, twenty-four-hour duration precipitation
plus 50%.
3.
Unless subsurface conditions prevent the use of infiltration BMPs per § 158-304A and B, at least the first 1.25 inches of runoff from impervious surfaces and 0.675 inch of runoff from pervious surfaces within the limit of disturbance shall be infiltrated as part of the required volume controls. If this infiltration volume exceeds the volume in § 158-306B.2.a.1 above, the infiltration volume itself shall be used as the total runoff volume that must be mitigated.
4.
For modeling purposes of volume controls, in addition to the modeling requirements of § 158-306A above:
a.
Volume shall be calculated using the NRCS Type-II Curve Number
runoff method (SCS).
b.
Nonstructural and other credits not directly representative
of a SWM facility's physical volume, including but not limited
to tree planting and impervious area disconnection, are prohibited
from being used in the modeling of volume controls.
b.
The Simplified Method (similar to CG-2 in the BMP Manual) provided
below is independent of site conditions, may only be used if the Design
Storm Method is not followed, and may only be used for regulated activities
requiring a minor SWM permit. For new impervious surfaces:
c.
Methodologies shall not be combined.
C.
Rate controls.
1.
Rate controls shall be required only for regulated activities requiring
a major SWM permit; regulated activities that require a minor SWM
permit are not required to provide rate controls.
2.
For areas that are not covered by a release rate map from an approved
Act 167 stormwater management plan, post-development peak discharge
rates shall not exceed the predevelopment peak discharge rates for
the five-, ten-, twenty-five-, fifty-, and 100-year storm events.
For the one- and two-year storm events, post-development peak discharge
rates shall not exceed 30% of the predevelopment peak discharge rate.
3.
For areas that are covered by a release rate map from an approved
Act 167 stormwater management plan, post-development peak discharge
rates shall not exceed the predevelopment peak discharge rates for
the five-, ten-, twenty-five-, fifty-, and 100-year storm events as
listed within the applicable, approved release rate map. For the one-
and two-year storm events, post-development peak discharge rates shall
not exceed the predevelopment peak discharge rates as listed within
the applicable, approved release-rate map or 30% of the predevelopment
peak discharge rate, whichever provides the greater amount of rate
reduction.
a.
For sites that are covered by two or more release rate areas,
the allowable peak discharge rate from any subareas shall be the predevelopment
peak discharge for that subarea multiplied by the applicable release
rate reduction for that subarea. Discharges from one release rate
district shall not be redirected to any other release rate district
without the explicit consent of the Municipal Engineer; such redirected
discharges, when allowed, shall comply with the more restrictive release
rate reduction from the existing or proposed discharge subarea.
b.
Due to frequent waterway, localized, storm sewer, and overland flooding in Palmer Township clearly showing inadequate downstream capacity for increased peak flows, the Township will not recognize conditional/provisional no-detention stormwater management designs in release rate districts so named; such areas shall comply with § 158-306C.2 above.
4.
For modeling purposes of rate controls, in addition to the modeling requirements of § 158-306A above:
a.
For regulated activities under 10 acres in size, the Modified
Rational Method or TR-55 may be used for the calculation of peak rates;
this ordinance shows no preference for either method. For regulated
activities above 10 acres in size, TR-55 shall be used.
b.
BMPs designed to have a permanent pool of water shall assume
that the permanent pool volume below the primary outlet is full at
the beginning of the design event routing for the purpose of evaluating
peak outflows.
c.
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 removed from peak runoff rates in
the post-development analysis. New, additional, contributing runoff
shall not be directed to existing sinkholes or closed depressions.
The following criteria shall apply to any use of property that
meets the definition of "hotspot." Noncommercial accessory uses incidental
to residential uses shall not be considered hotspot uses.
A.
All hotspot uses (as determined by the municipality on a case-by-case basis based upon the definition in Article II of this ordinance) shall include a stormwater pollution and prevention plan as part of the O&M plan. The stormwater pollution and prevention plan (SWPP) shall implement regular pavement sweeping, practice proper salt storage, maintain an on-site spill kit with oil booms, perform regular visual inspection of the site and SWM facilities, and report to the municipality every two years on the implementation and use of this plan.
1.
The following are typical hotspot land uses and acceptable pretreatment
method(s):
|
Hotspot Land Use
|
Pretreatment Method(s)
| |
|---|---|---|
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Vehicle maintenance and repair facilities including auto parts
stores
|
•
|
Water quality inlets
|
|
•
|
Use of drip pans and/or dry sweep material under vehicles/equipment
| |
|
•
|
Use of absorbent devices to reduce liquid releases
| |
|
•
|
Spill prevention and response program
| |
|
Vehicle fueling stations
|
•
|
Water quality inlets
|
|
•
|
Spill prevention and response program
| |
|
Storage areas for public works
|
•
|
Water quality inlets
|
|
•
|
Use of drip pans and/or dry sweep material under vehicles/equipment
| |
|
•
|
Use of absorbent devices to reduce liquid releases
| |
|
•
|
Spill prevention and response program
| |
|
•
|
Diversion of stormwater away from potential contamination areas
| |
|
Outdoor storage of liquids
|
•
|
Spill prevention and response program
|
|
Commercial nursery operations
|
•
|
Vegetated swales/filter strips
|
|
•
|
Constructed wetlands
| |
|
•
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Stormwater collection and reuse
| |
|
Other hotspot uses
|
•
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As determined for acceptability by the Municipal Engineer
|
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Other NPDES-regulated facilities
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•
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As required by the site's NPDES permit
|
B.
All hotspot uses shall utilize a "treatment train" that treats any
and all required stormwater management volumes in a series of at least
two water quality SWM BMPs before surface discharge.
C.
Infiltration of runoff from hotspot uses will only be allowed after
the runoff has been treated by one or more SWM BMPs, not including
the infiltration BMP itself, designed to treat the quality of stormwater
runoff based upon the pollutants expected at the hotspot use.
