Storm Water Technical Assistance

The Storm Water Technical Assistance Section assists local and state governments, developers, contractors, designers with controlling the negative impacts associated with new and existing development, including increased runoff, polluted storm water, stream erosion and loss of floodplain services. This section provides guidance for cost-effective and preventive measures (best management practices) that can be applied to limit these impacts during construction and after development. These practices control erosion and trap sediments during construction, treat pollutants from developed areas and reduce storm water runoff and protect downstream waters. Practice standards and specifications are available through the Rainwater and Land Development manual. Training for the development industry, as well as state and local government personnel, is offered for practice design, storm water management plan review and construction site inspection.

This section delivers economic, social and environmental value to Ohioans by helping developers and communities ensure projects minimize or mitigate environmental impacts in the most cost effective manner. For example, developers, contractors and local government employees are trained how to design, build and inspect storm water practices that reduce sediment, pollution and other impacts to Ohio’s streams and lakes.

Stream systems, including their corridors, and wetland resources are vital environmental features and are extremely sensitive to urbanization. The intent of this book is to allow development to occur while minimizing the impact to water resources, especially streams.

This manual defines Ohio’s standards and specifications for storm water practices implemented during land development. The target audience is that group of professionals involved in the design and implementation of development projects, but it is also used by others interested in implementing sound practices that minimize erosion, sediment and storm water impacts.

The manual integrates water resource protection into development site planning in order to maintain or improve stream integrity. Early chapters discuss practices and strategies for protecting streams and wetlands, treating storm water pollutants, and establishing permanent runoff controls. The latter chapters include chapters regarding construction-phase practices, including standards and specifications for sediment control, temporary runoff control, soil stabilization and control of pollutants other than sediment. Appendices offer additional important information for design such as storm water design examples, soils, planning around streams, and use of and impacts to soils.

NOTE: To register as a Rainwater and Land Development user, and/or to purchase printed manuals with binder for $50.00 + $10 (shipping and handling), contact us at

  • Phased Disturbance
  • Clearing and Grubbing
  • Tree and Natural Area Preservation
  • Construction Entrance
  • Dust Control
  • Grade Treatment
  • Top Soiling
  • Temporary Seeding
  • Mulching
  • Permanent Seeding
  • Sodding
  • Temporary Rolled Erosion Control Products (Erosion Control Matting)
  • Turf Reinforcement Matting

Manual Updates

The last entirely new edition of the Rainwater and Land Development manual was issued in November of 2006, but new materials have been added with changes and corrections made since that time. These are always included in new printings and in files posted to this site, but your manual may be older and need updating. Since 2012, updates have been indicated in the manual’s table of contents (Introductory Information) and is the best way to see what has been updated and when it occurred. You are encouraged to provide your name and contact information to us in order to receive news of updates and proposed changes for the manual (

Big Darby Creek Watershed

Darby water shed Location

The Big Darby Creek watershed is among the most biologically diverse stream systems of its size in the Midwest. Befitting this distinction, Ohio water quality standards regulations assign the most stringent aquatic life use designations (exceptional warmwater habitat and coldwater habitat) and the outstanding state water antidegradation category to many of the larger streams in the watershed. The watershed is home to several endangered species and Big and Little Darby Creeks are designated state and national scenic rivers.

However, recent studies document declines in water quality and stream habitat, some of which have been found to be directly related to construction activity. Among the most visible and widely publicized future threats to the Big Darby Creek watershed is conversion of farm land to suburban and commercial land uses, especially in Franklin County.

As a result, Ohio EPA has developed specific watershed conditions, found in Appendix A of OHC000005, for storm water associated with construction activity within the Big Darby Creek watershed. Appendix A implements many of the basic recommendations regarding the programs, activities and Best Management Practices developed through the Total Maximum Daily Load process and the State Water Quality Management Plan and 208 Plan. Ohio EPA believes implementation of these recommendations is necessary to protect the unique water quality and biological integrity of the Big Darby Creek system. 

Permit Compliance Materials

Related Documents

GIS Data for Download

Save the following .zip files to your computer's hard drive and use a program such as PKZIP or WINZIP to extract the files.

Stream Channel and Flood Plain Erosion

To control pollution of public waters by soil sediment from accelerated stream channel erosion and to control flood plain erosion caused by accelerated storm water runoff from development areas, the increased peak rates and volumes of runoff shall be controlled such that:

  1. The peak rate of runoff from the critical storm and all more frequent storms occurring on the development area does not exceed the peak rate of runoff from a one year frequency storm (of 24 hours duration) occurring on the same area under pre-development conditions.
  2. Storms of less frequent occurrence than the critical storm, up to the one hundred year storm, have peak runoff rates no greater than the peak runoff rates from equivalent size storms under pre-development conditions.

The critical storm for a specific development area is determined as follows:

  1. Determine by appropriate hydrologic methods the total volume of runoff from a one-year frequency, 24-hour storm occurring on the development area before and after development.
  2. From the volumes determined in (a), determine the percentage increase in volume of runoff due to development, and using this percentage, select the 24-hour critical storm from this table.

If the percentage of increase in volume of runoff is:

Equal to or Greater Than
and Less Than
the Critical Storm for Peak Rate Control will be

1 year
10 20 2 year
20 50 5 year
50 100 10 year
100 250 25 year
250 500 50 year
600 100 year


Download the Ohio Storm Water Control Guidebook


Central Office Storm Water Technical Assistance Staff

Mathews, John


(614) 265-6685

Reinhart, Justin

Water Resources Engineer

(614) 705-1149


Transportation Related Projects