Storm water

Definition of Storm water

Storm water is the discharge of water due to runoff from precipitation.  Storm water runoff occurs when precipitation from rain or snowmelt flows over impervious surfaces.  Impervious surfaces are areas that impede the infiltration of water into the soil.  Concrete, asphalt, rooftops and even severely compacted areas of soil are considered impervious. 

Storm water can pick up debris, chemicals, dirt, and other pollutants.  These substances are then carried into storm sewer systems or directly to a waterway.  This discharge can destroy aquatic habitat, lessen aesthetic value, and threaten public health with contaminated food, drinking water supplies, and recreational waterways. For more information on preventing waterways pollution go to Project Clean Rivers.

Storm water Pollution

The following are guidelines for preventing storm water pollution: 
  • Compost or mulch yard waste.  Don't leave it in the street or sweep into storm drains or streams.
  • Use lawn care products (ie: fertilizer, herbicides, and pesticides) sparingly.
  • Plant trees and vegetation.  The root system stabilized the ground and thus slowing runoff and erosion.
  • Properly dispose of household hazardous waste (ie: engine oils, paints, pesticides, etc), yard waste, pet waste, and kitchen grease.
  • Never dump anything into storm drains and sewers (it is illegal).
  • Keep drainage ditch and swales free of debris, litter, and obstructions.
  • Wash cars at a commercial wash or over areas of gravel or grass.
  • Sweep debris from sidewalks and driveways rather than washing debris away.
  • Report hazardous spills, illegal dumping, blockages, and unusual odors.

Gahanna Woods Detention Basin

The Gahanna Woods Detention Basin is located off of Taylor Station Rd just south of Havens Corners Rd.  The basin is part of the Gahanna Woods Park and is adjacent to the Gahanna Woods Nature Preserve.  It was built in 2012 to detain peak storm water flows and improve water quality in the stream.  Click here for more details.

Sycamore Run Stream Restoration

Residents along the lower reaches of the Sycamore Run Watershed have experienced high flows during storm events.  This in turn has caused stream erosion.  The area of the stream just south of the Hamilton Rd crossing has experienced severe erosion and floodplain degradation.  The has secured a federal grant to fund a stream restoration project.  The project consists of restoring over 1,000 feet of the Sycamore Run by stabilizing the stream channel, reconnecting the wooded floodplain and developing a stream habitat through native riparian plant species.  The project will ultimately be accessible to the public and will include a trail and interpretive signs.  Click here for more details.

Rain Gardens

A rain garden is an alternative way to alleviate storm water runoff.  Native plants in a rain garden slow the flow of storm water from impervious surfaces.  This allows the storm water to infiltrate the ground.  This prevents erosion and pollution distribution into the stream and river beds.  These gardens help eliminate pollutants, control erosion and prevent flooding.  It does all of this while adding the beauty of plants and flowers to your landscape. You can place rain gardens near downspouts, driveways, sump pump outlets or in the path of storm water flow through your yard.  The Rain Garden Initiative is a cost share program that will offer you up to $250 to install a rain garden on your property. This program is only available to six residents each year.  Click here to learn more about the program or call Franklin Soil and Water Conservation District at 614-486-9613.

Rain Barrels

A rain barrel is a drum barrel that is used as a cistern to collect and store rainwater from your roof.  This rainwater would otherwise be lost as runoff and flow into a storm drain.  Rain barrels are placed under a gutter downspout.  The water collected can then be used to water your lawn, water flowers, wash your car, top off a swimming pool, and other such activities.  One advantage of rain barrels is that they save homeowners money while conserving water and protecting the environment.  Gahanna was recently added to Franklin Soil and Water Conservation District’s GreenSpot Rain Barrel Program.  Click here to learn more about the program and to download the registration form.  If you need further information about the program you can call Franklin Soil and Water Conservation District at 614-486-9613.

NPDES Phase II Program

The City owns and maintains a system of storm drains and pipes that are designed to carry storm water (rain and snowmelt) from areas of potential flooding (ie: streets and parking lots) to the closest stream.  This system, which also includes roadside ditches, is known as a municipal separate storm sewer system or MS4 for short.  Unlike sanitary sewer systems, MS4s do not lead to a wastewater treatment plant.  They carry storm water directly, without treatment, to local waterways.

The U.S. Environmental Protection Agency and the Ohio Environmental Protection Agency enforce urban storm water regulations.  These regulations are associated with a program known as the National Pollutant Discharge Elimination System (NPDES).  This program requires local governments to develop a plan to reduce storm water pollution in order to protect and improve waterways.

The program is comprised of six control measures that will reduce pollutant discharge.  These include the following:

  • Public Education and Outreach: newsletters, websites, and workshops relating storm water issues
  • Public Participation and Involvement: programs and events that involve people in storm water management (ie: the rain garden initiative and stream cleanup days)
  • Illicit Discharge Detection and Elimination: ensures that only rainwater and snowmelt go down the drain
  • Construction Site Runoff Control: review construction project's site plans to certify sediment, excessive runoff, and pollution will not enter streams or waterways
  • Post-Construction Runoff Control: verify that runoff and pollution control structures are maintained
  • Pollution Prevention and Good Housekeeping: measures taken by the City to protect waterways (ie: street sweeping and catch basin maintenance)
The City is required to submit a NPDES report for their MS4 system every year to the Ohio EPA in order to receive a permit to allow storm water to enter streams and rivers.  Click here to review the Gahanna's 2013 NPDES report.

Illicit Discharge Detection and Elimination (IDDE) PLan

The Illicit Discharge Detection and Elimination (IDDE) Plan is a component of the National Pollutant Discharge Elimination System (NPDES) program described above.  This plan outlines how the City will find and eliminate pollutants that are entering the MS4 illegally to ensure that only rainwater and snowmelt go down the storm drain.  Pollutants are categorized as anything other than clean rainwater or snowmelt.  These ‘illicit discharges’ can enter through a storm drain on a street or parking lot, a pipe from a poorly functioning household sewage treatment system or a home or workplace drain connected to the MS4 instead of the sanitary sewer system.
The primary method that Gahanna uses to monitor pollutants entering its MS4 is dry-weather screening.  Inspectors check outfalls, where storm sewer pipes empty to local waterways.  If there has been no rain for a few days, and water is flowing from the pipes, where is it coming from?  If it is clean, it may be from groundwater infiltration or a small stream that was enclosed in a pipe during development.  Unfortunately, it is often from a poorly functioning septic system and is contributing nutrients, detergents and E. coli to a local stream.  Other instances of illicit discharge might be washing machines incorrectly draining into basement sumps, car repair or other small business floor drains connected to storm sewer lines and homeowners dumping paint, automotive fluids, dead leaves, pet waste, etc down curbside storm drains. 
Another important aspect of the City's IDDE plan is encouraging residents to report when they see or smell signs of pollutants in local streams or ditches.  If you see or smell signs of pollutants please contact the Department of Public Service at 614-342-4005 between 8:00 am and 5:00 pm, Monday through Friday. 
For more information and an opportunity to review the IDDE Plan, click here.  
The City welcomes public comments on the plan.  If you are interested in submitting comments, click here.

Storm water management plan

The City is required to submit a storm water management plan to the Ohio EPA during the first term of the permit cycle.  The report outlines the City's compliance status with permit regulations (such as NPDES), an evaluation of management procedures and analysis of progress goals.  The Storm Water Management Plan can be found by clicking here.

Additional Resources

Franklin Soil and Water Conservation District, FSWCD
Ohio Department of Natural Resources, ODNR:
Ohio Environmental Protection Agency, OhioEPA:


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