Article 949 DESIGN CRITERIA

Article 949
DESIGN CRITERIA

Sections:

949.01 Design criteria for stormwater management and drainage facilities.

A. General Design Guidelines.

1. Stormwater shall not be transferred from one watershed to another, unless (a) the watersheds are subwatersheds of a common watershed which join together within the perimeter of the property; (b) the effect of the transfer does not alter the peak rate discharge onto adjacent lands; or (c) easements from the affected landowner(s) are provided.

2. Consideration shall be given to the relationship of the subject property to the drainage pattern of the watershed. A concentrated discharge of stormwater to an adjacent property shall be within an existing watercourse or confined in an easement or returned to a predevelopment flow type condition.

3. Stormwater BMPs and recharge facilities are encouraged (e.g., rooftop storage, drywells, cisterns, recreation area ponding, diversion structures, porous pavements, holding tanks, infiltration systems, in-line storage in storm sewers, and grading patterns). They shall be located, designed, and constructed in accordance with the latest technical guidance published by PADEP, provided they are accompanied by detailed engineering plans and performance capabilities and supporting site specific soils, geology, runoff and groundwater and infiltration rate data to verify proposed designs. Additional guidance from other sources may be accepted at the discretion of the municipal engineer (a preapplication meeting is suggested).

4. All existing and natural watercourses, channels, drainage systems and areas of surface water concentration shall be maintained in their existing condition unless an alteration is approved by the appropriate regulatory agency.

5. The design of all stormwater management facilities shall incorporate sound engineering principles and practices. The City of Meadville shall reserve the right to disapprove any design that would result in the continuation or exacerbation of a documented adverse hydrologic or hydraulic condition within the watershed, as identified in the plan.

6. The design and construction of multiple use stormwater detention facilities are strongly encouraged. In addition to stormwater management, facilities should, where appropriate, allow for recreational uses including ball fields, play areas, picnic grounds, etc. Consultation with the City of Meadville and prior approval are required before design. Provision for permanent wet ponds with stormwater management capabilities may also be appropriate.

a. Multiple use basins should be constructed so that potentially dangerous conditions are not created.

b. Water quality basins or recharge basins that are designed for a slow release of water or other extended detention ponds are not permitted for recreational uses, unless the ponded areas are clearly separated and secure.

7. Should any stormwater management facility require a dam safety permit under PADEP Chapter 105, the facility shall be designed in accordance with Chapter 105 and meet the regulations of Chapter 105 concerning dam safety.

B. Stormwater Management Facility Design Considerations. All stormwater management facilities shall meet the requirements contained in the Crawford County stormwater management facility design criteria. (Ord. 3687, 2011)

949.02 Calculation methodology.

A. All calculations shall be consistent with the guidelines set forth in the BMP manual, as amended by standards established from time to time by the city engineer.

B. Stormwater runoff from all development sites shall be calculated using either the rational method or the NRCS rainfall-runoff methodology. Methods shall be selected by the design professional based on the individual limitations and suitability of each method for a particular site. (Ord. 3687, 2011)