For any of the regulated activities of this
Part 1, 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 requirements.
(1) A general description of the project.
(2) A general description of the proposed stormwater controls.
B. Map(s). Map(s) of the project area shall show the
following:
(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.
(3) Streams, lakes, ponds or other bodies of water within
the project area.
(4) Other physical features, including existing drainage
swales 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.
(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)
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 rooftop
storage, semipervious paving materials, grass swales, parking lot
ponding, vegetated strips, detention or retention ponds, storm sewers,
etc.
(c)
Water quality controls if necessary.
(2) All calculations, assumptions and criteria used in
the design of the control device or method must be shown.
D. Maintenance program. A maintenance program for all
stormwater management control facilities must be included. This program
must include the proposed ownership of the control facilities and
the maintenance requirements for the facilities and detail the financial
responsibility for the required maintenance.
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 Municipal Engineer) shall require a resubmission of the modified drainage plan consistent with §
125-27 subject to review per §
125-28 of this Part
1.
[Added 7-18-2006 by Ord. No. 295
A. Applicability of stormwater detention/storage requirements.
Stormwater detention/storage facilities or a fee in lieu of such facilities
shall be provided in accordance with the following provisions:
(1) Stormwater from any new impervious surfaces constructed
on an improved residential lot shall be controlled in accordance with
the following requirements:
(a)
Stormwater from new impervious surfaces that meets the exemption criteria set forth in §
125-7 of the Code of Whitpain Township, measured cumulatively from the date of adoption of this Part
1, shall be exempted from these requirements and does not need to be detained.
(b)
Stormwater from new impervious surfaces not
exempted shall be detained/stored through one of the following mechanisms:
[1]
Designed in accordance with underground infiltration
facilities for a small construction project.
[2]
Designed in accordance with all other provisions of Chapter
125 of the Code of the Township of Whitpain.
[3]
Payment of a fee in lieu of stormwater detention/storage
facilities.
B. Simplified stormwater control facilities. A detention
basin or underground infiltration basin that meets the following requirements
shall be provided for simplified stormwater management control:
(1) The detention basin shall provide 0.28 cubic feet of storage capacity for each one square foot of new impervious surface, or the underground stone infiltration basin shall provide 0.7 cubic feet of storage capacity for each one square foot of new impervious surface in accordance with §
125-7.
(2) The maximum depth of the detention basin shall be
four feet.
(3) The maximum side slopes of the detention basin shall
be three to one.
(4) An infiltration test shall be performed, such as a double ring infiltrometer
test, to determine the appropriate hydraulic conductivity rate. The
test shall be in compliance with the soil infiltration testing requirements
included in Appendix C.
[Added 1-4-2016 by Ord.
No. 345]
C. Fee-in-lieu alternative for detention/storage facilities.
(1) In order to address flooding and erosion problems found in all watersheds in Whitpain Township except the Wissahickon Creek Watershed, applicants may pay a fee in lieu of stormwater detention/storage facilities as an alternative to the construction of stormwater detention/storage facilities. When fees are offered by an applicant, the Township may, but shall not be required to, accept the fees, provided that the proposed stormwater solution meets the requirements in §
125-30.
[Amended 1-4-2016 by Ord.
No. 345]
(2) These fees shall be used to construct Township funded or sponsored
stormwater management facilities in all watersheds in Whitpain Township,
except the Wissahickon Creek Watershed. Additionally, such fees may
be used for the acquisition of land and rights-of-way, engineering,
legal and planning costs and all other costs, including debt service,
related to the construction of necessary stormwater control facilities.
[Amended 1-4-2016 by Ord.
No. 345]
(3) Applicants shall pay the following fees in lieu of
stormwater facilities:
(a)
Fees in lieu of stormwater detention/storage
facilities on an improved residential lot shall be based on the square
feet of new impervious surface area that will not be controlled. Such
fee shall be established at $2.50 per square foot as of the date of
the ordinance and updated annually based on the Consumer Price Index
(CPI-U published for the Greater Philadelphia area by the U.S. Department
of Labor).
(4) Fees collected by the Township shall be deposited
in an interest-bearing account in a bank authorized to receive deposits
of Township funds. Interest earned by the account shall be credited
to that account and shall be used for the same purposes as money deposited
in the account.