Post-construction storm water management is necessary because runoff from developed areas can significantly impact local streams and rivers if it is not properly managed. There are two general types of impacts that occur. First, there is typically an increase in some types and quantities of pollutants in storm water runoff. As water flows over these sites, it transports harmful contaminants such as oil and grease, pesticides, heavy metals, and various nutrients, (e.g., nitrogen and phosphorous). These pollutants become suspended in the runoff and are conveyed to receiving water bodies, such as lakes and creeks.
The second post-construction impact occurs as a result of increased storm water runoff volume and rates due to an increase in impervious (hard or paved) surfaces. The added impervious area reduces the amount of rain water that soaks into the ground, and speeds the flow of the water toward a storm drain or open channel. This can result both in localized and downstream flooding, as well as stream bank erosion, if management practices aren’t put in place to address the added volume and increased flow.
Post Construction BMPs can be structural or non-structural in nature. As the name implies, structural management practices are constructed measures and include such items as retention ponds, filter strips and rain water gardens.
However, it is not always necessary to construct a treatment practice to manage storm water runoff. Runoff problems can be addressed efficiently with sound planning procedures. Master Plans, Comprehensive Plans, and zoning ordinances can promote improved water quality by guiding growth of a community away from sensitive areas and by restricting certain types of growth (industrial, for example) to areas that can support it without compromising water quality. Non-structural management practices can include buffer strip and riparian zone preservation, minimization of disturbance and imperviousness, and maximization of open space.
BMP Manual
In 2004, Clermont County worked cooperatively with Sanitation District No. 1 of Northern Kentucky and the Louisville Metropolitan Sewer District to develop a manual of regional post-construction best management practices. The manual contains fact sheets for different BMPs, each of which includes information on the advantages and disadvantages of the BMP, its limitations, estimated costs, design specifications and maintenance requirements. Links to each individual fact sheet are provided to the right. (Note that the stream setback fact sheet is taken directly from the ODNR Rainwater Manual).
The fact sheets are not intended to provide engineering specifications for the BMPs. For more information on design specifications, the user should refer to the ODNR Rainwater and Development Manual (2006 edition).
Clermont County extends its thanks to Sanitation District No. 1 of Northern Kentucky and the Louisville MSD for their help in developing this manual. Clermont County would also like to express its gratitude and thanks to the Metropolitan Council of St. Paul, MN, on which this manual is strongly based, and the Metropolitan Government of Nashville and Davidson County, TN, Department of Public Works, Engineering Division for permission to use their Stormwater Management Manual.