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Post Construction

The intent of Post Construction Overflow Ditch Storm Water Management is to assure that storm water runoff from developed land does not negatively impact receiving streams, either through hydrologic impacts or pollutant discharges. Thus, traditional storm water controls which simply address the peak rate of storm water discharge from flood-producing storm events are not adequate. As land is developed, it becomes more impervious. Vegetation in open fields and forests is replaced with paved surfaces and rooftops. This results in more rainfall becoming storm water runoff. In addition, conveyance systems are installed to drain the site more efficiently resulting in storm water runoff with more energy than the runoff from undeveloped land. These hydrologic impacts, coupled with the increased concentration of pollutants contained in storm water runoff from developed land use, result in degradation of the water resources to which the storm water is discharged. The smaller the receiving stream, the greater the importance of controlling the hydrologic and subsequent hydraulic impacts of the construction project.

All storm water collection systems for any proposed site development involving one (1) acre or more of property shall be designed to meet the Ohio EPA’s Construction General Permit #OHC000005. Post-construction best management practices (BMPs) will need to be included with the site design to serve the site. Such practices for permanent site BMPs to meet the water quality requirements may include, but are not limited to: bioretention cells, storm water detention structures (both wet and dry extended detention basins), vegetated swales and vegetated filter strips designed using water quality flow, and sequential systems (which combine several practices). The design of Post-Construction storm water controls for the site shall be in accordance with the above referenced OEPA Construction General Permit. A list of standard BMPs is included in Tables 4a and 4b (pages 21 and 22 of 60) of the Construction General Permit. BMPs shall be designed according to the methodology included in the Ohio Department of Natural Resources (ODNR) Rainwater and Land Development Manual or in another design manual acceptable for use by Ohio EPA.

The design of Post-Construction storm water controls shall be in accordance with the Ohio EPA’s Construction General Permit #OHC000005, the City of Oregon’s Storm Water Management Plan, and Codified Ordinances of Oregon, Ohio Section 1177.06 Storm Sewers.

Design Resources

Storm Water Requirements for Site Plan Development, City of Oregon

ODNR’s Rainwater and Land Development Manual Development Manual (Ohio’s Standards for Stormwater Management Land Development and Urban Stream Protection)

Guidance Regarding Post-Construction Storm Water Management Requirements of Ohio EPA’s Storm Water Construction General Permit #OHC000002.