What is storm water? Is it the puddle our children splash in or maybe the little stream along the road after a downpour that runs into storm drains?
Storm Water is defined by the US Environmental Protection Agency (EPA) as urban runoff and snowmelt runoff, consisting only of those discharges which originate from precipitation events. Storm water is precipitation that flows across a surface to a storm drain system or receiving waters. Examples of this include: the water that flows off a building’s roof when it rains (runoff from an impervious surface); the water that flows into streams when snow on the ground melts (runoff from a semi-pervious surface); and the water that flows from a vegetated surface when rainfall exceeds the rate at which it can infiltrate into the soil (runoff from a pervious surface).
When something is pervious, it has the ability to allow a liquid to pass through. When all factors are equal, runoff increases as the surface becomes more impervious. For example, grass fields are more pervious and absorb more runoff than an asphalt parking lot.
During precipitation events in urban areas, rain water picks up and transports pollutants through storm water systems, and ultimately to waters of the Commonwealth. Examples of pollutants are motor oil or fuels from vehicles, soils and dust, winter de-icing materials, and spilled or dumped chemicals.
What is a Municipal Separate Storm Sewer System (MS4)?
Municipal Separate Storm Sewer Systems, as defined by EPA, are categorized by population, and Lower Paxton Township is defined as a small MS4. Under the Clean Water Act, the EPA developed a multi-year, multi-phase program called the National Pollution Discharge Elimination System (NPDES). Under Phase II of this program, small MS4s are required to obtain a permit for their storm water management system.
A storm water management system consists of any pipe, ditch or gully, or system of pipes, ditches, or gullies, owned or operated by a government and used for collecting and conveying storm water.
Lower Paxton Township’s storm water management system consists of tens of thousands of feet of pipe along with hundreds of manholes and inlets that discharge into private facilities or local waterways. Generally, storm water facilities located within a public right-of-way are the responsibility of the Township. Facilities outside a public right-of-way are the responsibility of a landowner or a Home Owners’ Association (HOA). There are instances of facilities located outside a public right-of-way where easements have been provided to the Township for maintenance.