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 applicant or his/her agent has received written approval of a drainage plan from the Township.
(Ord. 4-2004, 6/2/2004, §301)
1. Stormwater Quantity Control Exemption.
A. Chester Creek. Any regulated activity that meets the following exemption criterion shall not be required to submit a drainage plan implementing the stormwater quantity controls of this Chapter. This criterion shall apply to the total development even if the development is to take place in phases. The date of the Township Ordinance adoption shall be the starting point from which to consider tracts as "parent tracts" in which future subdivisions and respective impervious area computations shall be cumulatively considered. Exemption shall not relieve the applicant from implementing such measures as are necessary to protect health, safety, and property.
(1) Stormwater Management Exemption Criterion. No more than 10% of the total site area, up to a maximum of 2,000 square feet of additional impervious cover.
B. Ridley Creek. Any regulated activity that meets the following exemption criterion shall not be required to submit a drainage plan implementing the stormwater quantity-controls of this Chapter.
(1) Stormwater Management Exemption Criterion.
(a) Subdivisions or land developments that do not create more than 7,500 square feet of impervious land area.
(b) For parcels under single ownership, no more than one subdivision or land development creating less than 7,500 square feet of impervious surface shall be permitted before requiring a stormwater management for the entire parcel.
(c) Application procedures for exempt developments:
1) Persons engaged in land alteration of exempt development sites are exempt only from the full stormwater plan requirements of this Chapter. Applicants are responsible for applying sound storm- water management practices in accordance with the standards of this Chapter and the Pennsylvania Stormwater Act (Act 167) in the development of the site.
2) A sketch stormwater plan showing the location and nature of the proposed stormwater techniques for the site shall be submitted to the Township Engineer.
3) The stormwater plan for the site must be approved by the Engineer prior to the issuance of any building (or zoning use) permits.
2. Applicants whose activities are exempted under §19-302.A above shall at the request of the Township still be required to meet the stormwater management quality controls of this Chapter. This may be achieved by implementing one or more of the following minimum best management practices:
A. Provide infiltration capacity for the equivalent of 1 inch of runoff from all new impervious surfaces. The infiltration volume does not have to be provided in one location. However, if site conditions preclude capture of runoff from portions of the impervious area, the infiltration volume for the remaining area should be increased an equivalent amount to offset the loss. In no case should the portion of the new impervious area flowing to an infiltration facility be less than 70% of the total new impervious area.
B. If site conditions preclude use of infiltration facilities (e.g., high groundwater table or extensive rock conditions), provide an extended detention facility that will detain the equivalent of 1 inch of runoff from all new impervious areas for at least 24 hours.
C. Provide buffer areas on the downstream side of any new impervious surfaces (e.g., sidewalks, roadways, parking lots) where the runoff discharges in a sheet flow manner. The buffer areas should be at least 20 feet wide and can be a mix of grass, shrubs, and trees. If buffer areas cannot be provided for the entire length of the impervious surfaces, consider installing a bio-retention system and diverting surface runoff from the impervious surfaces to the facility using grass swales.
(4) If none of the above options are feasible due to site constraints, the applicant must provide stormwater detention that meets the release rate criteria for the site location or else obtain approval from the Township Engineer to implement other BMPs that will provide water quality benefits of an equivalent level.
3. New Federal regulations approved October 1999 require operators of small municipal separate storm sewer systems (MS4s) to obtain NPDES Phase II permits from DEP by March 2003. (NPDES II is an acronym for the National Pollutant Discharge Elimination System Phase II Stormwater Permitting Regulations.) This program affects all municipalities in "urbanized areas" of the State. This definition applies to all Chester Creek and Ridley Creek watershed municipalities. Therefore, all municipalities regulated by this Chapter will be subject to the NPDES Phase II requirements mandated by the Federal Clean Water Act as administered by DEP. For more information on NPDES II requirements, contact the DEP Regional Office.
(Ord. 4-2004, 6/2/2004, §302)
For all activities regulated by this Chapter, the steps below shall be followed for submission. For any activities that require a DEP joint permit application and are regulated under Chapter 105 (Darn Safety and Waterway Management) or Chapter 106 (Floodplain Management) of DEP's Rules and Regulations, require a PennDOT highway occupancy permit, or require any other permit under applicable State or Federal regulations, the permit(s) shall be part of the plan.
A. Five copies of the drainage plan and associated plan review application shall be submitted by the applicant as part of the Act 247 preliminary plan submission for the regulated activity. Distribution of the drainage plan will be as follows:
(1) Two copies to the Township accompanied by the requisite Township review fee, as specified in this Chapter.
(3) One copy to the County Planning Department.
(4) One copy to the County Conservation District.
(Ord. 4-2004, 6/2/2004, §303)
1. The drainage 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 drainage plan materials shall be submitted to the Township in a format that is clear, concise, legible, neat, and well organized; otherwise, the drainage plan shall be disapproved and returned to the applicant.
The following items shall be included in the drainage plan:
A. 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.
(3) Complete hydrologic, hydraulic, and structural computations for all stormwater management facilities.
B. Map(s) of the project area shall be submitted on 24 inch x 36 inch sheets and shall be prepared in a form that meets the requirements for recording at the offices of the Recorder of Deeds of Delaware 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) Existing contours at intervals of 2 feet.
(3) Existing streams, lakes, ponds, or other bodies of water and wetlands within the project area.
(4) Other physical features including flood hazard boundaries, streams, existing drainage courses, areas of natural vegetation to be preserved, and the total extent of the upstream area draining through the site.
(5) The locations of all existing and proposed structures and utilities within 200 feet of property lines.
(6) An overlay showing soil names and boundaries.
(7) Proposed changes to the land surface and vegetative cover, including the type and amount of impervious area that would be added.
(8) Proposed structures, roads, paved areas, and buildings.
(9) Final contours at intervals of 2 feet.
(10) 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.
(11) The date of the plan, including revisions.
(12) A graphic and written scale at a minimum of 1 inch equals no more than 50 feet.
(13) A north arrow.
(14) The total tract boundary and size with distances marked to the nearest foot and bearings to the nearest degree.
(15) Existing and proposed land use(s).
(16) Vertical profiles of all proposed open channels and storm sewers including hydraulic capacity for both.
(17) Overland drainage paths of proposed swales or channels to convey water.
(18) A note on the plan indicating the location, access, and responsibility for maintenance of stormwater management facilities.
(19) 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.
"(Design Engineer), on this date (date of signature), has reviewed and hereby certifies that the drainage plan meets all design standards and criteria of the Act 167 Stormwater Management Plan, Chester Creek Watershed, Model Stormwater Management Ordinance and/or the Act 167 Ridley Creek Watershed Stormwater Management Ordinance and all applicable Township ordinances.
C. 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.
1) A soil erosion and sedimentation control plan, where applicable, including all reviews and approvals, as required by DEP.
2) The effect of the project (in terms of runoff volumes and peak flows) on adjacent properties and on any existing Township storm- water collection system that may receive runoff from the project site.
(2) Stormwater Management Facilities.
a) All stormwater management facilities must be located on a plan and described in detail.
b) When groundwater recharge methods such as seepage pits, beds, or trenches are used, the locations of existing and proposed septic tank infiltration areas and wells must be shown.
c) All calculations, assumptions, and criteria used in the design of the stormwater management facilities must be shown.
(Ord. 4-2004, 6/2/2004, §304)
1. The Township Engineer shall review the drainage plan for consistency with the adopted Chester Creek Stormwater Management Plan, Ridley Creek Stormwater Management Plan and this Chapter. The Township shall require receipt of a complete plan, as specified in this Chapter. The Township Engineer shall review the drainage plan for any submission or land development against the Township subdivision and land development ordinance provisions not superseded by this Chapter.
2. The Conservation District, in accordance with established criteria and procedures, shall review the drainage plan for consistency with stormwater management and erosion and sediment pollution control requirements and provide comments to the Township. Such comments shall be considered by the Township prior to final approval of the drainage plan.
3. For activities regulated by this Chapter, the Township Engineer shall notify the Township in writing as to whether the drainage plan is consistent with the watershed's respective Stormwater Management Plan. Should the drainage plan be determined to be consistent with the watershed's respective Stormwater Management Plan, the Township Engineer will forward an approval letter to the applicant with a copy to the Township Secretary.
4. Should the drainage plan be determined to be inconsistent with the Storm- water Management Plan, the Township Engineer will forward a disapproval letter to the applicant with a copy to the Township Secretary citing the reason(s) for the disapproval. Any disapproved drainage plans may be revised by the applicant and resubmitted consistent with this Chapter.
5. For regulated activities specified in §19-104 of this Chapter, the Township Engineer shall notify the Township Building Permit Officer in writing, within a time frame consistent with the Township Building Code [Chapter 5] and/or Township Subdivision Ordinance [Chapter 22], as to whether the drainage plan is consistent with the watershed's respective stormwater management plan and forward a copy of the approval/disapproval letter to the applicant. Any disapproved drainage plan may be revised by the applicant and resubmitted consistent with this Chapter.
6. For regulated activities requiring a DEP joint permit application, the Township Engineer shall notify DEP as to whether the drainage plan is consistent with the watershed's respective stormwater management plan and forward a copy of the review letter to the Township and the applicant. DEP may consider the Township Engineer's review comments in determining whether to issue a permit.
7. The Township shall not approve any subdivision or land development for regulated activities specified in §19-104 of this Chapter if the drainage plan has been found to be inconsistent with the watershed's respective stormwater management plan, as determined by the Township Engineer. All required permits from DEP must be obtained prior to approval.
8. The Township Building Permit Officer shall not issue a building permit for any regulated activity specified in §19-104 of this Chapter if the drainage plan has been found to be inconsistent with the watershed's respective stormwater management plan, as determined by the Township Engineer, or without considering the comments of the Township Engineer. All required permits from DEP must be obtained prior to issuance of a building permit.
9. The applicant shall be responsible for completing as-built drawings of all stormwater management facilities included in the approved drainage plan. The as-built drawing and an explanation of any discrepancies with the design plans shall be submitted to the Township Engineer for final approval.
10. The Township's approval of a drainage plan shall be valid for a period not to exceed 5 years. This 5-year period shall commence on the date that the Township signs the approved drainage plan. If stormwater management facilities included in the approved drainage plan have not been constructed, or if as-built drawings of these facilities have not been approved within this 5-year time period, then the Township may consider the drainage plan disapproved and may revoke any and all permits. Drainage plans that are considered disapproved by the Township shall be resubmitted in accordance with §19-307 of this Chapter.
(Ord. 4-2004, 6/2/2004, §305)
1. A modification to a submitted drainage plan for a development site that involves a change in stormwater management facilities or techniques, or that involves the relocation or re-design of stormwater management facilities, or that 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 §19-304 of this Chapter and be subject to review as specified in §19-305 of this Chapter.
2. A modification to an already approved or disapproved drainage plan shall be submitted to the Township, accompanied by the applicable review fee. A modification to a drainage plan for which a formal action has not been taken by the Township shall be submitted to the Township, accompanied by the applicable Township review fee. (Ord. 4-2004, 6/2/2004, §306)
A.disapproved drainage plan may be resubmitted, with the revisions addressing the Township Engineer's concerns documented in writing, to the Township Engineer in accordance with §19-304 of this Chapter and be subject to review as specified in §19-305 of this Chapter. The applicable Township review fee must accompany a resubmission of a disapproved drainage plan.
(Ord. 4-2004, 6/2/2004, §307)
1. All regulated activities within the Chester Creek Watershed and Ridley Creek Watershed, and in the Township which do not fall under the exemption criterion shown in §19-302 shall submit a drainage plan consistent with this Chapter to the Township for review. This criterion shall apply to the total proposed development even if development is to take place in stages. Impervious cover shall include, but not be limited to, any roof, parking, or driveway areas and any new streets and sidewalks. Any areas designed to initially be gravel or crushed stone shall be assumed to be impervious.
2. Drainage plans shall be prepared in accordance with the provisions contained in this Article. The process for implementing these provisions is illustrated in Figure 4-1, 'Water Quality and Quantity Control Drainage Plan Preparation Procedures."
3. This Chapter requires water quality and water quantity controls as illustrated on the flow chart shown in Figure 4-1 and detailed in §19-404. The flow chart illustrates a three-step hierarchical process: Step 1- Infiltration, Step 2 - Extended Detention, and Step 3 - Implementation of Additional Design Controls. Applicants must evaluate the outcome of each step before proceeding to the next. In addition, riparian buffers are required where applicable, in accordance with §19-404.1.B.
4. Applicants are highly encouraged to meet the post-development peak discharge control criteria indicated in §§19-402 and 403 through use of BMPs and innovative site designs that minimize the amount of new impervious surface.
(Ord. 4-2004, 6/2/2004, §401)
