All activities involving land disturbance, whether
or not a plan is prepared or a permit obtained in accordance with
this chapter, shall be consistent with good engineering practice and
the following performance standards:
A.
All land disturbance activities shall be conducted
in such a way as to prevent accelerated erosion and resulting sedimentation.
To accomplish this, all persons engaged in land disturbance activities
shall design, implement and maintain erosion and sedimentation control
measures which effectively prevent accelerated erosion and sedimentation.
B.
In order to prevent accelerated erosion and resulting
sedimentation, land disturbance activities relating to construction,
farming operations, nursery and sod operations and logging operations
shall be conducted only in conformity with the following:
[Amended 1-5-1998 by Ord. No. 221]
(1)
Land disturbances related to construction activities.
All land-disturbing activities related to construction, including
but not limited to construction of buildings or other structures and
paving activities, shall be conducted only in conformity with the
following:
(a)
Erosion and sedimentation devices such as temporary
vegetation/mulch, temporary detention basins, diversion terraces,
rock filter berms or hay bales (in areas of minimum flows) appropriate
to the scale of operations shall be provided where necessary.
(b)
No earthmoving shall be conducted in areas greater
than 25% slope unless written approval is obtained from the Township
Engineer.
(c)
Earthmoving will not involve the addition or
removal of soil, rock or fill material to or from more than 10% of
a developed site (containing a business or residential structure)
or 30% of an undeveloped site at any one time until stabilized, unless
approved, in writing, by the Township Engineer.
(d)
Changes in grades and topography shall be limited and will not involve more than 30% of the area of a site nor create slopes greater than 10 feet in 100 feet except as provided in Appendix A, Section I, Subsection A, unless approved, in writing, by the Township Engineer.
(e)
Stripping of vegetation, regrading or other
development shall be done in such a way that will minimize erosion.
(f)
Development plans shall preserve salient natural
features, keep cut or fill operations to a minimum and ensure conformity
with topography to create the least erosion potential and to adequately
handle the volume and velocity of surface runoff.
(g)
Whenever feasible, natural vegetation shall
be retained, protected and supplemented.
(h)
The amount of disturbed area and the duration
of exposure shall be kept to a practical minimum.
(i)
The permanent (final) vegetation and structural
erosion control and drainage measures shall be installed as early
as practical during the development.
(j)
Sediment in the runoff water shall be trapped
and removed to assure adequate capacity in the basins or traps, as
required by the Township Engineer.
(k)
Procedures for protecting soils or geologic
structures with water supply potential from contamination by surface
water or other disruption by construction activities shall be established
(see Appendix A, Section II).
(2)
Farming operations. All farming operations shall be
conducted only in conformity with the following:
(a)
Plowing shall conform to the contours of the
property.
(b)
Drainage swales shall be maintained with permanent
cover with grasses, plants or trees.
(c)
Permanent cover shall be maintained within a
minimum of 20 feet of a stream and 10 feet up-slope from property
lines.
(d)
If livestock are watered from a stream, methods
to protect the stream bank from erosion will be provided in areas
of animal concentration.
(e)
Runoff from buildings and other impervious surfaces
shall be diverted around areas where livestock are confined or tillage
crops are planted or shall be otherwise controlled.
(f)
Tillage shall not be conducted on slopes exceeding
15%, except where minimum tillage methods approved by the Soil Conservation
District have been approved.
(g)
Diversion terraces or cover crops of no less
than 10 feet in width shall be provided at a maximum of two-hundred-foot
intervals on slopes of 8% to 15% where tillage crops are planted.
(h)
Except where over-winter crops are planted,
minimum tillage methods are used, as approved by accepted agricultural
standards, or cover crop strips are established, fall plowing is prohibited.
(i)
Any earthmoving other than plowing shall conform
to the earthmoving standards.
(3)
Nursery and sod operations. All nursery and sod operations
shall be conducted only in conformity with the following:
(a)
Runoff from buildings and other impervious surfaces
shall be diverted around areas where sod or plants are regularly removed.
(b)
Drainage swales shall be maintained with permanent
cover of grasses, plants or trees.
(c)
Diversion terraces or permanent cover strips
of no less than 10 feet in width shall be provided or maintained on
the contours at a maximum of two-hundred-foot intervals on slopes
exceeding 8% from which sod or nursery stock will be regularly removed.
(d)
Permanent cover grasses or plants shall be maintained
within a minimum of 20 feet of a stream or road right-of-way and a
minimum of 30 feet up-slope from abutting property lines.
(e)
Areas where sod is being reworked must be promptly
seeded, planted or otherwise stabilized within 15 days of disturbance.
(4)
Logging and woodcutting operations. All logging operations
conducted for profit or in conjunction with or prior to a land development,
subdivision or farm operation shall be conducted only in conformity
with the following:
(a)
Stumps, ground cover and root mat must be left
intact, except where land is being developed or farmed.
(b)
Methods of removal of logs and the removal routes
shall be specified in a plan, approved by the Township Engineer, and
shall avoid the the use of tracked vehicles. Slopes of 15% to 25%
shall be traversed at the minimum gradient possible.
(c)
On slopes of 15% to 25%, logging shall involve
less than 1/3 of uniform aged and noncontiguous trees.
(d)
On slopes exceeding 25%, logging and woodcutting
shall be by written approval of the Board of Supervisors and shall
be limited to highly selective removal of trees. Maximum precautions
shall be taken to avoid destruction or injury of understory brush
and trees.
(e)
No cutting of live trees within 20 feet of closest
bank of any stream is permitted.
C.
The design requirements for controlling erosion and
sedimentation for construction are set forth in Appendices A and B
attached to this chapter and made a part hereof.
All activities described in § 148-7 involving an increase in impervious cover shall be consistent with the following performance standards:
A.
There shall be no increase in stormwater peak discharge
after installation of impervious cover over and above that which would
have occurred from the land prior to development, using woodland as
the prior condition for those portions of the site that have trees
of over six inches DBH (or had such trees within a year prior to application)
and meadowland for all other areas, assuming average antecedent moisture
conditions and a Type II distribution storm under any of the following
storm conditions:
(1)
A two-year, twenty-four-hour storm of 3.2 inches of
rainfall.
(2)
A five-year, twenty-four-hour storm of 4.2 inches
of rainfall.
(3)
A ten-year, twenty-four-hour storm of 5.0 inches of
rainfall.
(4)
A twenty-five-year, twenty-four-hour storm of 5.7
inches of rainfall.
(5)
A fifty-year, twenty-four-hour storm of 6.4 inches
of rainfall.
(6)
A one-hundred-year, twenty-four-hour storm of 7.12
inches of rainfall.
B.
Storm sewer systems for conveyance of stormwater shall
be designed to a ten-year design storm, except at sumps, in which
case the system shall be sized to carry a twenty-five-year design
storm. In addition, there shall be adequate provision made to safely
handle all storms in excess of the required design storm (up to the
one-hundred-year storm) to prevent significant damage when the system
fails. Inundation of yards or periodic basement flooding is not considered
significant damage. Any bridge or culvert proposed to be within a
major streambed shall be designed to safely carry the one-hundred-year
design storm in conjunction with normal base flow without causing
flood or erosion damage to the surrounding properties. No provisions
within this chapter shall limit or otherwise affect the requirements
of the Floodplain Ordinance.[1]
C.
All plans and designs for stormwater management facilities
submitted to the Township Engineer for approval shall determine stormwater
peak discharge and runoff by the use of the Soil Cover Complex Method,
as set forth in Urban Hydrology for Small Watersheds, Technical Release
No. 55, with specific attention given to antecedent moisture conditions,
flood routing and peak discharge specifications included therein,
and Hydrology National Engineering Handbook, Section 4, both by United
States Department of Agriculture, Soil Conservation Service.
D.
In calculating runoff after development, those areas
covered by concrete lattice blocks on an appropriate base, as outlined
in Appendix B, Section II, and roofs which drain to properly designed
and installed seepage beds shall not be considered to be impervious
surfaces. Concrete lattice blocks, seepage beds for roof drainage
or similar provisions to reduce runoff shall be required under the
following conditions:
(1)
Whenever total impervious surfaces (buildings, parking
areas, driveways, etc.) will exceed 15% of the lot coverage on a residential
lot, driveways shall be constructed of concrete lattice blocks or
other equivalent provision shall be made to reduce runoff which is
accepted by the Township Engineer.
(2)
Whenever total impervious surfaces in a residential
land development will exceed 8% or whenever total impervious surfaces
in other types of land development will exceed 20%, the following
facilities designed in accordance with Appendix B shall be provided
to hold or infiltrate roof drainage:
E.
In order to prevent an increase in the rate of stormwater
runoff under design conditions, the installation of impervious cover
shall be effected only in conformity with the following:
(1)
Erosion and sediment control and stormwater management
control facilities shall be incorporated into all building site designs
and the overall design of any subdivision or land development or improvement
so they may serve purposes such as wildlife areas, recreational areas
and fire prevention ponds.
(2)
The natural infiltration and water resource potentials
of various soil and geologic formations shall guide design, construction
and vegetation decisions (Appendix A, Section II). Runoff in excess
of natural conditions from roofs, lawn areas and other surfaces which
are unlikely to contain pollutants shall be recharged to the groundwater
table or stored for nonpotable water uses.
(3)
All existing trees and shrubs, natural streams, channels,
drainage swales and areas of surface water concentration shall be
maintained in their existing conditions, except where changes can
be justified on the basis of other design standards of this chapter.
