A.
All regulated earth disturbance activities within
Whitpain Township shall be designed, implemented, operated and maintained
to meet the purposes of this Part 1, through these two elements:
B.
No regulated earth disturbance activities within Whitpain
Township shall commence until the requirements of this Part 1 are
met.
C.
Erosion and sediment control during regulated earth disturbance activities shall be addressed as required by § 125-11.
E.
All best management practices (BMPs) used to meet
the requirements of this Part 1 shall conform to the state water quality
requirements, and any more stringent requirements as determined by
Whitpain Township.
F.
Techniques for low-impact development, as hereinafter
set forth, are encouraged to be implemented because they reduce the
costs of complying with the requirements of this Part 1 and the state
water quality requirements.
G.
Low-impact development practices alternative approach
for managing stormwater runoff.
(1)
Natural hydrologic conditions may be altered radically
by poorly planned development practices, such as introducing unneeded
impervious surfaces, destroying existing drainage swales, constructing
unnecessary storm sewers, and changing local topography. A traditional
drainage approach of development has been to remove runoff from a
site as quickly as possible and capture it in a detention basin. This
approach leads ultimately to the degradation of water quality as well
as expenditure of additional resources for detaining and managing
concentrated runoff at some downstream location.
(2)
The recommended alternative approach is to promote
practices that will minimize postdevelopment runoff rates and volumes,
which will minimize needs for artificial conveyance and storage facilities.
To simulate predevelopment hydrologic conditions, forced infiltration
is often necessary to offset the loss of infiltration by creation
of impervious surfaces. The ability of the ground to infiltrate depends
upon the soil types and its conditions.
(3)
Preserving natural hydrologic conditions requires
careful alternative site design considerations. Site design practices
include preserving natural drainage features, minimizing impervious
surface area, reducing the hydraulic connectivity of impervious surfaces,
and protecting natural depression storage. A well-designed site will
contain a mix of all those features. The following describes various
techniques to achieve the alternative approach:
(a)
Preserving natural drainage features. Protecting
natural drainage features, particularly vegetated drainage swales
and channels, is desirable because of their ability to infiltrate
and attenuate flows and to filter pollutants. However, this objective
is often not accomplished in land development. In fact, commonly held
drainage philosophy encourages just the opposite pattern; streets
and adjacent storm sewers typically are located in the natural headwater
valleys and swales, thereby replacing natural drainage functions with
a completely impervious system. As a result, runoff and pollutants
generated from impervious surfaces flow directly into storm sewers
with no opportunity for attenuation, infiltration, or filtration.
Developments designed to fit site topography also minimizes the amount
of grading on site.
(b)
Protecting natural depression storage areas.
Depressional storage areas have no surface outlet, or drain very slowly
following a storm event. They can be commonly seen as ponded areas
in farm fields during the wet season or after large runoff events.
Traditional development practices eliminate these depressions by filling
or draining, thereby obliterating their ability to reduce surface
runoff volumes and trap pollutants. The volume and release-rate characteristics
of depressions should be protected in the design of the development
site. The depressions can be protected by simply avoiding the depression
or by incorporating its storage as additional capacity in required
detention facilities.
(c)
Avoiding introduction of impervious areas. Careful
site planning should consider reducing impervious coverage to the
maximum extent possible. Building footprints, sidewalks, driveways
and other features producing impervious surfaces should be evaluated
to minimize impacts on runoff.
(d)
Reducing the hydraulic connectivity of impervious
surfaces. Impervious surfaces are significantly less of a problem
if they are not directly connected to an impervious conveyance system
(such as storm sewer). Two basic ways to reduce hydraulic connectivity
are routing of roof runoff over lawns and reducing the use of storm
sewers. Site grading should promote increasing travel time of stormwater
runoff, and should help reduce concentration of runoff to a single
point in the development.
(e)
Routing roof runoff over lawns. Roof runoff
can be easily routed over lawns in most site designs. The practice
discourages direct connections of downspouts to storm sewers or parking
lots. The practice also discourages sloping driveways and parking
lots to the street. By routing roof drains and crowning the driveway
to run off to the lawn, the lawn is essentially used as a filter strip.
(f)
Reducing the use of storm sewers. By reducing
use of storm sewers for draining streets, parking lots, and back yards,
the potential for accelerating runoff from the development can be
greatly reduced. The practice requires greater use of swales and may
not be practical for some development sites, especially if there are
concerns for areas that do not drain in a reasonable time. The practice
requires educating local citizens and public works officials, who
expect runoff to disappear shortly after a rainfall event.
(g)
Reducing street widths. Street widths can be
reduced by either eliminating on-street parking or by reducing roadway
widths. Municipal planners and traffic designers should encourage
narrower neighborhood streets which ultimately could lower maintenance.
(h)
Limiting sidewalks to one side of the street.
A sidewalk on one side of the street may suffice in low-traffic neighborhoods.
The lost sidewalk could be replaced with bicycle/recreational trails
that follow back-of-lot lines. Where appropriate, backyard trails
should be constructed using pervious materials.
(i)
Using permeable paving materials. These materials
include permeable interlocking concrete paving blocks or porous bituminous
concrete. Such materials should be considered as alternatives to conventional
pavement surfaces, especially for low-use surfaces such as driveways,
overflow parking lots, and emergency access roads.
(j)
Reducing building setbacks. Reducing building
setbacks reduces driveway and entry walks and is most readily accomplished
along low-traffic streets where traffic noise is not a problem.
(k)
Constructing cluster developments. Cluster developments
can also reduce the amount of impervious area for a given number of
lots. The biggest savings is in street length, which also will reduce
costs of the development. Cluster development clusters the construction
activity onto less sensitive areas without substantially affecting
the gross density of development.
(4)
In summary, a careful consideration of the existing
topography and implementation of a combination of the above-mentioned
techniques may avoid construction of costly stormwater control measures.
Other benefits include reduced potential of downstream flooding, water
quality degradation of receiving streams/water bodies and enhancement
of aesthetics and reduction of development costs. Beneficial results
include more stable base flows in receiving streams, improved groundwater
recharge, reduced flood flows, reduced pollutant loads, and reduced
costs for conveyance and storage.
The following permit requirements may apply
to certain regulated earth disturbance activities, and must be met
prior to commencement of regulated earth disturbance activities, as
applicable:
A.
All regulated earth disturbance activities subject
to permit requirements by DEP under regulations at 25 Pa. Code Chapter
102.
C.
Any stormwater management facility that would be located in or adjacent to surface waters of the commonwealth, including wetlands, subject to permit by DEP under 25 Pa. Code Chapter 105.
D.
Any stormwater management facility that would be located
on a state highway right-of-way, or require access from a state highway,
shall be subject to approval by the Pennsylvania Department of Transportation
(PENNDOT).
A.
No regulated earth disturbance activities within Whitpain
Township shall commence until approval by Whitpain Township of an
erosion and sediment control plan for construction activities.
B.
DEP has regulations that require an erosion and sediment
control plan for any earth disturbance activity of 5,000 square feet
or more, under 25 Pa. Code § 102.4(b).
C.
In addition, under 25 Pa. Code Chapter 92, a DEP NPDES
construction activities permit is required for regulated earth disturbance
activities.
D.
Evidence of any necessary permit(s) for regulated earth disturbance activities from the appropriate DEP regional office or County Conservation District must be provided to Whitpain Township. The issuance of an NPDES construction permit or [permit coverage under the statewide general permit (PAG-2)] satisfies the requirements § 125-11A.
E.
A copy of the erosion and sediment control plan and
any required permit, as required by DEP regulations, shall be available
at the project site at all times.
A.
No regulated earth disturbance activities within Whitpain
Township shall commence until approval by Whitpain Township of a plan
which demonstrates compliance with state water quality requirements
after construction is complete.
B.
The BMPs must be designed, implemented and maintained
to meet state water quality requirements, and any other more stringent
requirements as determined by Whitpain Township.
C.
To control postconstruction stormwater impacts from
regulated earth disturbance activities, state water quality requirements
can be met by BMPs, including site design, which provide for replication
of preconstruction stormwater infiltration and runoff conditions,
so that postconstruction stormwater discharges do not degrade the
physical, chemical or biological characteristics of the receiving
waters. As described in the DEP Comprehensive Stormwater Management
Policy (#392-0300-002, September 28, 2002), this may be achieved by
the following:
(1)
Infiltration: replication of preconstruction stormwater
infiltration conditions;
(2)
Treatment: use of water quality treatment BMPs to
ensure filtering out of the chemical and physical pollutants from
the stormwater runoff; and
(3)
Stream bank and streambed protection: management of
volume and rate of postconstruction stormwater discharges to prevent
physical degradation of receiving waters (e.g., from scouring).
D.
DEP has regulations that require municipalities to
ensure design, implementation and maintenance of best management practices
(BMPs) that control runoff from new development and redevelopment
after regulated earth disturbance activities are complete. These requirements
include the need to implement postconstruction stormwater BMPs with
assurance of long-term operations and maintenance of those BMPs.
E.
Evidence of any necessary permit(s) for regulated earth disturbance activities from the appropriate DEP regional office must be provided to Whitpain Township. The issuance of an NPDES construction permit [or permit coverage under the statewide general permit (PAG-2)] satisfies the requirements of § 125-12A.
