For any of the regulated activities described
in this chapter, prior to the final approval of subdivision and/or
land development plans, or the issuance of any permit, or the commencement
of any land disturbance activity, the owner, subdivider, developer
or his agent shall submit a drainage plan for approval.
The following items shall be included in the
drainage plan:
A. General.
(1) General description of project.
(2) General description of proposed permanent stormwater
controls.
B. Map(s) of the project area showing:
(1) The location of the project relative to highways,
municipalities or other identifiable landmarks.
(2) Existing contours at intervals of two feet. In areas
of steep slopes (greater than 15%), five-foot contour intervals may
be used. Off-site drainage areas impacting the project including topographic
detail.
(3) Streams, lakes, ponds or other bodies of water within
the project area.
(4) Other physical features including existing drainage
swales, wetlands, closed depressions, sinkholes, and areas of natural
vegetation to be preserved.
(5) Locations of proposed underground utilities, sewers
and water lines.
(6) An overlay showing soil types and boundaries based
on the Northampton County Soil Survey, latest edition.
(7) Proposed changes to land surface and vegetative cover.
(8) Proposed structures, roads, paved areas and buildings.
(9) Final contours at intervals of two feet. In areas
of steep slopes (greater than 15%), five-foot contour intervals may
be used.
(10)
Fencing (if required) and landscaping screens.
(11)
Stormwater management district boundaries applicable
to the site.
C. Stormwater management controls.
(1) All stormwater management controls must be shown on
a map and described, including:
(a)
Groundwater recharge methods such as seepage
pits, beds or trenches. When these structures are used, the locations
of septic tank infiltration areas and wells must be shown.
(b)
Other control devices or methods such as roof-top
storage, semipervious paving materials, grass swales, parking lot
ponding, vegetated strips, detention or retention ponds, storm sewers,
etc.
(2) All calculations, assumptions and criteria used in
the design of the stormwater management facilities and in the establishment
of the calculated predevelopment and postdevelopment peak discharge,
including mapping of the watershed areas and indication of runoff
for all points of runoff concentration shall be provided.
(3) All plans and profiles of proposed stormwater management
facilities including horizontal and vertical location, size, and type
of material. This information shall provide sufficient information
required for the construction of all facilities.
(4) A map(s) clearly delineating and labeling all drainage
areas used in the design of storm sewer facilities, swales, and retention/detention
basins.
(5) For all detention and retention basins, a plotting
or tabulation of storage volumes with corresponding water surface
elevations and of the outflow rates for those water surfaces.
(6) For all detention and retention basins, the design
inflow and outflow hydrographs or the shortcut routing method to determine
the function of the basin.
(7) For all retention basins which hold 2 1/2 acre feet
or more of water and have an embankment that is 10 feet or more in
height, soil structures and characteristics shall be investigated.
Plans and data prepared by a registered professional, experienced
and educated in soil mechanics, shall be submitted.
(8) A map(s) clearly delineating any existing wetlands
as classified by a qualified environmental scientist experienced in
wetland determination. Wetland determination shall be performed in
accordance with U.S. Army Corps of Engineers procedures as outlined
in publication TRY-87-1, "Wetlands Delineation Manual," latest edition.
No construction or development shall be permitted in wetlands without
approval from the U.S. Army Corps of Engineers and the Pennsylvania
Department of Environmental Protection, Bureau of Dams and Waterway
Management.
D. Proposals for the ownership and maintenance responsibilities
for all proposed storm drainage and erosion and sediment control facilities
shall be submitted to the Township for review and approval at preliminary
plan stage. The Township shall be satisfied that sufficient provisions
have been made for adequate and perpetual maintenance of all such
facilities. All drainage facilities to be owned by the developer or
his assigns shall be maintained to retain their design capacity. Such
assurances shall be in a form to act as a covenant that shall run
with the land, and shall provide for municipal maintenance, assessment
of cost and penalties, in case of lack of maintenance.
A modification to a submitted drainage plan for a proposed development site which involves a change in control methods or techniques, or which involves the relocation or redesign of control measures, or which is necessary because soil or other conditions are not as stated on the drainage plan (as determined by the Township Engineer) shall require a resubmission of the modified drainage plan consistent with §
138-19 subject to review per §
138-20 of this chapter.