The design standards outlined in this article
shall be utilized by developers, surveyors, and engineers in preparing
subdivision plans, and will be applied by the Board of Lawrence Township
Supervisors when reviewing plans for approval. These standards shall
be considered as minimum standards for the developer to comply with
in the design, development, and improvement of a subdivision. Where
strict compliance with the standards is clearly impractical due to
site conditions, the Township Supervisors may modify the standards
to permit reasonable utilization of the property while securing substantial
compliance with the intent and purpose of these regulations.
[Amended 3-16-2010 by Ord. No. 2010-02]
Subdivision and land development plans shall include measures
that direct stormwater into the natural drainage system serving the
area. The following standards shall apply to stormwater drainage within
Lawrence Township:
A. Lots shall be laid out and graded to provide positive drainage away
from buildings. The Township may require a grading and drainage plan
for individual lots indicating a buildable area within each lot, complying
with the setback requirements, for which positive drainage is assured.
B. No person, corporation, or other entity shall block, impede the flow
of, alter, construct any structure in, deposit any material or thing
in, or commit any act which will affect normal or flood flow in any
communal stream or watercourse without having obtained prior approval
from Lawrence Township or the Department of Environmental Protection,
whichever is applicable.
C. Where a subdivision or land development is traversed by a natural
watercourse, there shall be provided a drainage easement or right-of-way
conforming substantially with the line of such watercourse and of
such width as will be adequate to preserve natural drainage.
D. The Township will ensure that all permanent streams not under the
jurisdiction of other official agencies are maintained, open and free
flowing.
E. The subdivider or developer, and each person, corporation, or other
entity which makes any surface changes in excess of 5,000 square feet,
shall be required to prepare and submit a stormwater management plan
for review and acceptance by the Township Engineer. The stormwater
management plan shall be in accordance with any Township stormwater
management ordinance and shall contain provisions for the following:
(1) Collecting on-site surface runoff and disposing of it at the point
of discharge into the common natural watercourse of the drainage area;
(2) Drainage facilities to handle runoff from upstream areas;
(3) Drainage structures and facilities as are necessary to prevent erosion
damage to the subdivision or land development, adjacent property and
downstream property. Such structures and facilities shall satisfactorily
convey surface waters to the nearest practical street, storm drain,
detention pond, or natural watercourse.
F. Storm sewers, culverts, and/or related installations shall be provided
to permit unimpeded flow of natural watercourses, to drain all low
points along streets and to intercept stormwater runoff along streets
at intervals reasonably related to the extent and grade of the area
drained.
G. Storm sewers, when required, shall be placed in front of the curb
or curbline when located in a street right-of-way. When located in
undedicated land, they shall be placed within an easement not less
than 15 feet wide, as accepted by the Township Engineer.
H. Street drainage will not be permitted to cross intersections or the
crown of the road.
(1) Maximum spacing of street inlets shall not exceed 600 feet.
(2) All street inlets shall be PennDOT Type C or M. Inlet tops shall
be cast-in-place reinforced concrete or precast concrete.
(3) All culvert ends shall be provided with either reinforced concrete
headwalls or pipe end sections.
(4) Minimum pipe size shall be a fifteen-inch diameter.
(5) When material for a storm drain is not specified, PennDOT specifications
will govern.
I. All springs and sump-pump discharges shall be collected so as not
to flow onto any cartway.
J. Stormwater roof drains shall not discharge water directly over a
sidewalk.
K. Stabilized outlets shall be provided for drains and downspouts.
L. The Soil Cover Complex Method of the Natural Resources Conservation
Service (NRCS) of the U.S. Department of Agriculture and the Rational
Method are the acceptable means of estimating stormwater runoff and
for designing or analyzing stormwater management facilities. The actual
method for each subdivision and land development shall be determined
and directed by the Township Engineer.
M. Where the estimated runoff based upon the above methods is doubtful,
several recognized methods should be studied and compared.
N. The minimum design criteria for ditches, swales, driveway cross pipes
and storm sewers shall be designated using the Rational Method and
shall be sized to accommodate a ten-year, five-minute design storm
unless otherwise approved by the Township Engineer. Drainage ditches,
swales, etc. shall be of sufficient depth to accommodate driveway
cross pipes and pipe culverts.
O. Runoff calculations must include complete hydrologic analysis for
pre- and post-development conditions and hydraulic design and analysis
of all control facilities. The analysis shall be performed for two-,
ten-, twenty-five-, and one-hundred-year-year storm frequencies. This
shall include, but not necessarily be limited to: rating curves, and
stage-storage and routing computations for stormwater management facilities.
P. Control facilities shall adhere to the following and/or any Township
stormwater management ordinance:
(1) Permanent control measures/facilities shall be designed to ensure
that the maximum rate of stormwater runoff is not greater after development
than prior to development. Detention and retention basins shall have
a spillway to protect the berm by precluding overtopping. The spillway
capacity shall, at a minimum, be capable of handling the one-hundred-year
storm while providing two feet of freeboard. More stringent criteria
may be required in sensitive areas where stormwater problems presently
exist.
(2) Control facilities shall be designed to meet, at a minimum, the design
standards and specifications of the Erosion and Sedimentation Control
Handbook for Clearfield County.
(a)
Detention ponds may not be required by the Township on the recommendation
of the Township Engineer at sites in close proximity to the major
streams, provided that computations are prepared and submitted for
review and comment. Said computations shall demonstrate that no increase
in peak rates of runoff will result from the proposed activity for
the specified storms.
(b)
Detention ponds shall be prohibited in areas of known sinkholes
unless the pond is lined. If a sinkhole develops in a pond or channel
before acceptance by the municipality, a lining shall be required.
(c)
All detention ponds shall be provided with a fence of a type
and height subject to approval of the municipality and shall be designed
to ensure access for maintenance.
(d)
All detention ponds shall be provided with a suitable access
road as approved by the Township.
(3) On-lot subsurface detention facilities (seepage pits, etc.) shall
be used to the extent practicable in minor subdivisions subject to
the acceptance of the Township Engineer. Roof drain seepage pits must
provide at least one cubic foot of storage volume for every two square
feet of roof area. Roof drain seepage pits shall be located at a minimum
of 10 feet from any structure, shall have a maximum depth of four
feet and shall include provisions for emergency overflow to prevent
property damage.
(4) A maintenance program for control facilities must be included as
part of the stormwater management plan.
(a)
Maintenance during development activities of a project shall
be the responsibility of the contractor, developer, and owner.
(b)
Permanent ownership and continuing operation and maintenance
of all proposed stormwater control facilities shall be consistent
with the following principles:
[1]
If a development consists of structures or lots which are to
be separately owned and in which streets, drainage facilities and
other public improvements are to be dedicated to the municipality,
stormwater control facilities should also be dedicated to and maintained
by the municipality.
[2]
If a development site is to be maintained in single ownership
or if drainage facilities and other required improvements are to be
privately owned and maintained, then the ownership and maintenance
of stormwater control facilities should be the responsibility of the
owner or private management entity.
[3]
The Township Supervisors, upon recommendation of the Township
Engineer, shall make the final determination on the ownership and
continuing maintenance responsibilities prior to final approval of
the stormwater management plan. The governing body reserves the right
to accept the ownership and operating responsibility for any or all
of the stormwater management controls.
If the developer proposes to reserve an area
for public use (i.e., schools, parks, other neighborhood and public
facilities), the following standards shall be applied to the character,
extent and location of the reserved area:
A. Such areas shall be labeled on the plan as "reserved,"
and shall indicate the particular type of public use for which the
area is being reserved.
B. Areas reserved for public use shall be accessible
through frontage on a public street and/or pedestrian rights-of-way
at least 10 feet in width, and be a suitable size and location for
their designated uses.
C. The developer must establish and assure the future
ownership of the permanent, public use, as well as indicate the provisions
for the maintenance of the area. Additionally, the Township may accept
the dedication of such land or any interest therein for public use
and maintenance.