Township of Plumstead, PA Stormwater Management Plan Requirements.

A feasibility analysis that evaluates the potential application of infiltration, flow attenuation, bioretention, wetland, or wet pond BMPs must be submitted with the required 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 § 26-129;

(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. The 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 [Subsections A(1)(b) and (c) above] and the general design standards and maintenance issues included in this Part, 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);

(i)

Rationale for the decision to not proceed with implementation of wet pond or artificial wetland BMPs such as insufficient soil suitability; and

(j)

Rationale for not proceeding with infiltration-oriented BMPs in accordance with §§ 26-124 and 26-127 of this Part.

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. Taking into consideration the areal extent of suitable soils necessary to accommodate an infiltration facility, wet pond or wetland BMP for the type and size of development proposed, developers are required to conduct the detailed soil testing and other feasibility testing required in other sections of this Part which contain the description and additional design criteria of these BMPs.

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.

Whenever a stormwater management facility will be located in an area underlain by limestone or dolomite, 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 lowerodibility factors ("K" factors). Installation of an impermeable liner shall be required in detention or retention basins constructed over limestone formations.

It shall be the developer's responsibility to verify whether 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."

General.

General description of project.

General description of permanent stormwater BMPs and 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 Part, written justification for use of these BMPs must be submitted.

Complete hydrologic, hydraulic, and structural computations for all stormwater management facilities.

Maps 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 map(s) shall include, but not be limited to:

The location of the project relative to highways, municipalities, or other identifiable landmarks.

Watershed(s) within which the project is located [e.g., Tohickon Creek, Neshaminy Creek, Delaware River (South)].

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 waterlines 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. The 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.

(12)

The date of submission.

(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.

(14)

A North arrow.

(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)

Overland drainage paths.

(20)

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 Part.

(22)

A construction detail of any improvements made to sinkholes and the location of all notes to be posted, as specified in this Part.

(23)

A statement on the plan, signed by the landowner, acknowledging the stormwater BMPs and management facilities 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 Plumstead Township Stormwater Management Ordinance."

Required Supplemental Information.

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 Part.

(c)

Stormwater management BMPs to be applied both during and after development.

(d)

Expected project time schedule.

A soil erosion and sedimentation control plan, where applicable, including all reviews and approvals, as required by PADEP and/or the Bucks County Conservation District.

A geologic assessment of the effects of runoff on sinkholes as specified in this Part.

(4)

The effect of the project (in terms of runoff volume, peak flow, and discharge durations) on adjacent properties and on any existing Township stormwater collection system that may receive runoff from the project site.

(5)

A declaration of adequacy and highway occupancy permit from the PennDOT District Office when utilization of a PennDOT 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.

Stormwater Management BMPs.

All stormwater management BMPs must be located on a plan and profile drawings and described in detail.

When infiltration methods such as seepage pits, beds, or trenches are proposed, the locations of existing and proposed septic tanks, 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.

All calculations, assumptions, and criteria used in the design of the stormwater management BMPs 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.

§ 26-138 Plan Submission.

[Ord. No. 2022-01, 7/12/2022]

For all activities regulated by this Part, the steps below shall be followed for submission. For any activities that require a PADEP joint permit application and regulated under Chapter 102 (Erosion and Sediment Control), Chapter 105 (Dam Safety and Waterway Management), or Chapter 106 (Floodplain Management) of PADEP's Rules and Regulations, require a PennDOT 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.

The stormwater management plan shall be submitted by the developer as part of the preliminary plan submission for the regulated activity.

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.

Distribution of the stormwater management plan will be as follows:

One hard copy to be retained by the Township, accompanied by the requisite Township review fee and escrow, as specified in this Part.