Zoning/Building Permits

Storm Water Review

The City of Meadville has been designated an MS4 (Municipal Separate Storm Sewer System) municipality by EPA and DEP. As such we are required to regulate the storm water generated within the corporate boundaries of the City. The following guidelines are presented to help the developer and his engineer determine the necessary storm water controls.

Watershed Areas:

Developments which discharge storm water into a watershed of the City of Meadville not listed below shall incorporate Best Management Practices (BMP’s) into the design of the facility. Examples of structural and non-structural BMP’s are included in chapters 5 and 6 of “Pennsylvania Stormwater Best Management Practices Manual”. This manual is available from the Pennsylvania Department of Environmental Protection. Storm water retention, storage, or infiltration shall be provided so that the post-development flows do not exceed the pre-development storm water discharge.

Neason Run

Any development which discharges storm water into this watershed shall incorporate Best Management Practices (BMP’s) into the design of the facility. Storm water retention, storage, or infiltration shall be provided so that the post-development flows do not exceed the pre-development storm water discharge

UNT of French Creek Crossing Baldwin, Lord, and Terrace Streets.

Any development which discharges storm water into this watershed shall incorporate Best Management Practices (BMP’s) into the design of the facility. Storm water retention, storage, or infiltration shall be provided so that the post-development flows do not exceed the pre-development storm water discharge.

French Creek

Any development which discharges storm water directly into French Creek shall incorporate Best Management Practices (BMP’s) into the design of the facility.

Watershed Standards/Calculation Methods

For the purpose of computing peak flow rates and runoff hydrographs from development sites, calculations shall be performed using one of the following: Soil Cover Complex (SCC) Method, Technical Release (TR) 55 or 20, or the HEC 1 or Penn State Runoff Model (PSRM). Under special circumstances the City Engineer may approve the use of other computation methods.

Predevelopment Conditions: Predevelopment conditions shall be assumed to be those which existed on any site at the time prior to the commencement of any development activities. Where a site has been developed previously and is proposed to be redeveloped, the predevelopment coefficient for the developed portion of the site shall be based upon an assumed fifty percent (50%) native land cover (i.e. grass, trees, etc) and fifty percent (50%) developed land cover (e.g., buildings, pavement, etc.). SCS runoff curve numbers selected for use in the calculations shall accurately reflect existing conditions subject to the approval of the City Engineer.

Watershed Standards/Release Rates/Procedures for Use

Storm Frequencies: Storm water management facilities for all development sites shall control the peak storm water discharge for the 2-, 10-, 25-, and 100-year storm frequencies. The Soil Conservation Service (SCS) 24-hour, Type II Rainfall Distribution shall be used for analyzing storm water runoff for both pre- and post-development conditions. The 24-hour total rainfall for these storm frequencies are as follows:

Storm Frequency Rainfall Depth (inches)

2-year 2.50 inches

10-year 3.60 inches

25-year 4.10 inches

100-year 4.80 inches

1. Release Rate Percentage: The release rate percentage defines the amount of pre-development peak rate of runoff that can be discharged from the outfall on a site after development under the 2-, 10-, and 25-year storm conditions. Under all circumstances, a 100% release rate percentage shall be applied to the 100-year frequency storm whether or not reduced release rates are specified for other return rates.

Procedure: Compute the pre- and post-development runoff hydrographs for each storm water outfall on the development site using an approved method for the required storm frequencies. Apply no on-site detention for storm water management, but include any techniques to minimize impervious surfaces and/or increase the time of concentration for storm water runoff flowing from the development site. If the post-development runoff rate and the runoff volume are less than or equal to the pre-development peak runoff rate and volume, then additional storm water control shall not be required for that outfall.

If the post-development peak runoff rate and/or volume are greater than the predevelopment peak runoff rate and/or volume, then storm water detention shall be required. The capacity of the detention facility shall be calculated by multiplying the pre-development rate of runoff from the 2-,10-, and 25-year frequency storm by the subarea release rate percentage and the predevelopment runoff rate from the 100 year storm event by 100% to determine the maximum allowable releases from any detention facility.

Parking:

Parking lots serving five (5) spaces or less shall provide storm water controls for both quantity and quality. The developer may utilize the City of Meadville’s standard design for storm water control. In lieu of using this standard, the developer may install a system of his choosing which meets the standards established by the City Engineer. Alternative designs must be prepared by an engineer licensed to practice in the Commonwealth of Pennsylvania.

Parking lots serving more than five (5) spaces shall provide storm water controls for both quantity and quality. The system shall be designed to meet the standards established by the City Engineer as previously described. Alternative designs must be prepared by an engineer licensed to practice in the Commonwealth of Pennsylvania.