For any of the activities regulated by this chapter, the final
approval of subdivision and/or land development plans, the issuance
of any building or occupancy permit, or the commencement of any land-disturbance
activity may not proceed until the property owner or developer or
his/her agent has received written approval of a stormwater management
plan from the Township.
The stormwater management plan shall consist of all applicable
calculations, maps, and plans. A note on the maps shall refer to the
associated computations and erosion and sedimentation control plan
by title and date. The cover sheet of the computations and erosion
and sedimentation control plan shall refer to the associated maps
by title and date. All stormwater management plan materials shall
be submitted to the municipality in a format that is clear, concise,
legible, neat, and well organized; otherwise, the stormwater management
plan shall be disapproved and returned to the applicant. The following
items shall be included in the stormwater management plan:
A. Feasibility analysis.
(1) A feasibility analysis that evaluates the potential application of
infiltration, flow attenuation, bioretention, wetland, or wet pond
BMPs must be submitted with the stormwater management plans for those
developments not intending the use of such facilities. This analysis
shall provide:
(a)
A general assessment of the anticipated additional runoff based on the design storm and post-development condition and utilizing the calculation procedures required in §
134-21;
(b)
Indication of drainage areas on the development site resulting
in impervious, pervious, and rooftop runoff;
(c)
Indication of type of land use (residential, nonresidential)
generating the impervious surface runoff;
(d)
Delineation of soils on the site from the NRCS, Soil Survey
of Bucks and Philadelphia Counties and on-site soil study. Soil study
shall be conducted by a soil scientist and shall include sufficient
probes/deep holes to evaluate application of BMPs;
(e)
Indication of soils generally suitable for infiltration and/or
wet pond/artificial wetland BMPs, including specification of those
soils requiring modifications;
(f)
Calculated acreage of suitable soils for infiltration BMPs and
wet pond or artificial wetland BMPs and percentage of suitable soils
based on total site acreage;
(g)
Calculated acreage of suitable soils for infiltration BMPs and
wet pond or artificial wetland BMPs made unavailable due to proposed
development layout and justification that alternative development
layout which would reduce impact on suitable soil availability is
unfeasible;
(h)
Analysis of potential infiltration or wet pond or artificial wetland BMPs which could be implemented to manage the projected post-development runoff with consideration of suitable soil availability runoff point of and type of land use (Subsection
A(1)(b) and
(c) above) and the general design standards and maintenance issues included in this chapter, including an indication of how most post-development runoff can be managed by these BMPs (e.g., the entire post-development runoff or partial amount of runoff expressed as a percentage); and
(i)
Rationale for the decision to not proceed with implementation
of infiltration BMPs or wet pond or artificial wetland BMPs such as
excessive cost of implementation, insufficient soil suitability, and
development constraints.
(2) The feasibility analysis must allow the Township to review the general
soil characteristics of a site and the proposed development for that
site and determine if infiltration BMPs or wet pond or artificial
wetland BMPs could have been more thoroughly pursued for use by the
developer. The information required in the analysis is detailed enough
to determine the potential applicability of these BMPs for a proposed
development, but general enough not to force a developer into incurring
excessive cost associated with conducting laborious field and/or laboratory
soil testing for a site which ultimately may not be suitable for infiltration
or wet pond or artificial wetland BMP implementation. However, with
the requirements for conducting a feasibility analysis, developers
will be aware that they are expected to use these BMPs wherever possible
and are required to provide adequate justification if these BMPs are
not to be implemented. Essentially, all developers will be conducting
feasibility analysis since such analysis would become the preliminary
step in evaluating the potential for implementation of these mandatory
BMPs where possible. Developers for those sites that are determined
to be generally suitable from these analyses (taking into consideration
the areal extent of suitable soils necessary to accommodate an infiltration
or wet pond or wetland BMP for the type and size of development proposed)
are required to conduct the detailed soil testing and other feasibility
testing required in other sections of this chapter which contain the
description and additional design criteria of these BMPs.
B. A detailed geologic evaluation of the project site shall be performed
to determine the suitability of recharge facilities. The evaluation
shall be performed by a qualified geologist and/or soil scientist
and, at a minimum, address soil permeability, depth to bedrock, susceptibility
to sinkhole formation, and subgrade stability.
C. Whenever a stormwater management facility will be located in an area
underlain by limestone, a geological evaluation of the proposed location
shall be conducted to determine susceptibility to sinkhole formations.
The design of all facilities over limestone formations shall include
measures to prevent groundwater contamination and, where necessary,
sinkhole formation. Soils used for the construction of basins shall
have low-erodibility factors (K factors). Installation of an impermeable
liner shall be required in detention basins. It shall be the developer's
responsibility to verify if the site is underlain by limestone. The
following note shall be attached to all stormwater management plans
and signed and sealed by the developer's professional engineer:
"I, ____________, certify that the proposed stormwater management
facility (circle one) is/is not underlain by limestone."
D. General.
(1) General description of project.
(2) General description of permanent stormwater management techniques,
including construction specifications of the materials to be used
for stormwater management facilities. If BMPs other than green infrastructure
methods and LID practices are proposed to achieve the volume, rate,
and water quality controls of this chapter, written justification
for use of these BMPs must be submitted.
(3) Complete hydrologic, hydraulic, and structural computations for all
stormwater management facilities.
E. Map(s) of the project area shall be submitted on twenty-four-inch
by thirty-six-inch sheets and shall be prepared in a form that meets
the requirements for recording at the offices of the Recorder of Deeds
of Bucks County. The contents of the maps(s) shall include, but not
be limited to:
(1) The location of the project relative to highways, municipalities,
or other identifiable landmarks.
(2) Watershed(s) within which the project is located (e.g., Tohickon
Creek, Neshaminy Creek, East Branch Perkiomen Creek).
(3) Existing contours at intervals of two feet. In areas of steep slopes
(greater than 25%), five-foot contours may be used.
(4) Existing streams, lakes, ponds, or other bodies of water within the
project area.
(5) Other physical features, including flood hazard boundaries, sinkholes,
streams, existing drainage courses, wetlands, areas of natural vegetation
to be preserved, and the total extent of the upstream area draining
through the site.
(6) The locations of all existing and proposed utilities, sanitary sewers,
and water lines located on the site and/or within 50 feet of property
lines with minimum setback distances for all existing and proposed
water supply wells and on-lot sewage disposal systems.
(7) An overlay showing soil names and boundaries. This overlay shall
include a table on the map showing the recharge capabilities of each
soil represented on-site in inches per hour and describe their recharge
or infiltration capabilities.
(8) Proposed changes to the land surface and vegetative cover, including
the type and amount of impervious area that would be added.
(9) Proposed structures, roads, paved areas, and buildings. Where pervious
pavement is proposed for parking lots, recreational facilities, nondedicated
streets, or other areas, pavement construction specifications shall
be noted on the plan.
(10)
Final contours at intervals at two feet. In areas of steep slopes
(greater than 25%), five-foot contour intervals may be used.
(11)
The name of the development, the name and address of the owner
of the property, and the name of the individual or firm preparing
the plan.
(13)
A graphic and written scale of one inch equals no more than
50 feet. For tracts of 20 acres or more, the scale may be one inch
equals no more than 100 feet.
(15)
The total tract boundary and size with distances marked to the
nearest foot and bearings to the nearest degree.
(16)
Existing and proposed land use(s).
(17)
A key map showing all existing man-made features beyond the
property boundary that may be affected by the project.
(18)
Horizontal and vertical profiles of all open channels, including
hydraulic capacity.
(19)
All existing and proposed stormwater management facility and/or
drainage easements described by metes and bounds, including the purpose
and ownership of each easement.
(21)
A note on the plan indicating the location and responsibility
for maintenance of stormwater management facilities that would be
located off-site. All off-site facilities shall meet the performance
standards and design criteria specified in this chapter.
(22)
A construction detail of any improvements made to sinkholes
and the location of all notes to be posted, as specified in this chapter.
(23)
A statement, signed by the landowner, acknowledging the stormwater
management system to be a permanent fixture that can be altered or
removed only after approval of a revised plan by the Township, which
shall be recorded with the record plan and which shall be applicable
to all future landowners.
(24)
The location of all erosion and sedimentation control facilities.
(25)
The following signature block for the design engineer:
(Design engineer), on this date (date of signature), has reviewed
and hereby certifies that the stormwater management plan meets all
design standards and criteria of the Hilltown Township Stormwater
Management Ordinance.
F. Required supplemental information.
(1) A written description of the following information shall be submitted:
(a)
The overall stormwater management concept for the project.
(b)
Stormwater runoff computations as specified in this chapter.
(c)
Stormwater management techniques to be applied both during and
after development.
(d)
Expected project time schedule.
(2) A soil erosion and sedimentation control plan, where applicable,
including all reviews and approvals, as required by PADEP and/or Bucks
Conservation District.
(3) A geologic assessment of the effects of runoff on sinkholes as specified
in this chapter.
(4) The effect of the project (in terms of runoff volume, peak flow,
and discharge duration) on adjacent properties and on any existing
municipal stormwater collection system that may receive runoff from
the project site.
(5) A declaration of adequacy and highway occupancy permit from the PADOT
District Office when utilization of a PADOT storm drainage system
is proposed.
(6) An operations and maintenance (O&M) plan for all existing and
proposed physical stormwater facilities, as well as schedules and
costs for O&M activities. The plan shall address long-term ownership
and responsibilities for O&M.
G. Stormwater management BMPs.
(1) All stormwater management facilities must be located on a plan and
profile drawings and described in detail.
(2) When infiltration methods such as seepage pits, beds, or trenches
are proposed, the locations of existing and proposed septic tank infiltration
areas and wells must be shown. A minimum separation distance of no
less than 20 feet shall be provided between any septic system and
any facility used for stormwater management. An analysis shall be
submitted to verify that stormwater infiltration shall not affect
groundwater elevations of the septic drain field site.
(3) All calculations, assumptions, and criteria used in the design of
the stormwater management facilities must be shown. If multiple facilities
are proposed in conjunction with each other, such as infiltration
best management practices with vegetation-based management practices,
a summary narrative shall be included describing any sequence and
how the facilities are meant to function with each other to manage
stormwater runoff.
For all activities regulated by this chapter, the steps below
shall be followed for submission. For any activities that require
a PADEP joint permit application and regulated under Chapter 105 (Dam
Safety and Waterway Management) or Chapter 106 (Floodplain Management)
of PADEP's Rules and Regulations, require a PADOT highway occupancy
permit, or require any other permit under applicable local, state,
or federal regulations, the permit(s) shall be part of the plan submission.
A. The stormwater management plan shall be submitted by the developer
as part of the preliminary plan submission for the regulated activity.
B. A minimum of two hard copies and one digital (PDF) copy of the stormwater
management plan and associated reports/documents shall be submitted
to the Township during regular business hours. Additional copies shall
be submitted if requested by the Township.
C. Distribution of the stormwater management plan will be as follows:
(1) One copy to the municipality accompanied by the requisite municipal
review fee, as specified in this chapter.
(2) One copy forwarded by the Township to the Township Engineer.
A set of design plans approved by the Township shall be on file
at the site throughout the duration of the development activity. Periodic
inspections may be made by the Township or designee during development
activities.
It shall be unlawful for any person to undertake any regulated
activity on any property except as provided for in the approved stormwater
management plan and pursuant to the requirements of this chapter.
It shall be unlawful to alter or remove any BMP required by the stormwater
management plan pursuant to this chapter or to allow the property
to remain in a condition which does not conform to the approved stormwater
management plan.
At the completion of the project, and as a prerequisite for the release of the performance guarantee under §
134-41, the owner or his representatives shall:
A. Contact the Township Engineer to request inspection of the site for
completion of stormwater management facilities and compliance with
the approved plans and specifications.
B. Provide a set of as-built drawings as required pursuant to the Township
Building Code and/or Subdivision and Land Development Ordinance.
A disapproved stormwater management plan may be resubmitted, with the revisions addressing the Municipal Engineer's concerns documented, in writing, to the Municipal Engineer in accordance with §
134-28 of this chapter and be subject to review as specified in §
134-29 of this chapter. The applicable municipal review fee must accompany a resubmission of a disapproved stormwater management plan.
An occupancy permit shall not be issued unless the stormwater
management facilities approved for the lot have been installed and
found satisfactory to the Township Engineer.