Stormwater

Proper stormwater management is key to flood prevention. In the early 1990’s, the State of Delaware adopted regulations which required developers to control the quantity of stormwater runoff for land development projects. Such regulations state that water should leave the post-developed site, during specific storm events, at the pre-development flow rate.

Not only are good stormwater management practices key to managing water quantity, but they are also significant in improving water quality. Those same regulations, designed to manage stormwater quantity, contain requirements that are intended to manage the pollutant levels in stormwater runoff. During a 1” rainstorm, 27,000 gallons of water falls across a single acre of land. There are 10,600 acres of impervious area in the Christina River Watershed alone, which is just 1 of the 21 watersheds in New Castle County. That’s over 286 million gallons of runoff that needs to be properly managed to protect water quality.

Pursuant to Delaware Code, Stormwater management facilities have been designed to improve both stormwater quantity and quality. Since July of 1991, enforcement of the Codes and regulations which governs such facilities, has been delegated to New Castle County. Per Federal and State laws, the Department. of Public Works is responsible for annually inspecting over 2,700 Stormwater Management Facilities located in the County.

Public Works Inspectors conduct field inspections of each facility, a minimum of once per year, to ensure that the facilities are functioning per their design. Property owners are advised, via mailed inspection reports, of any maintenance and repairs needed, to return the facility to its approved plan condition. If facilities are not maintained properly, corrective actions may be taken.

There are many different types of stormwater management practices. The type that is implemented depends upon onsite-specific conditions such as, compatibility with the proposed development, location in a drainage watershed, and existing land conditions. The following stormwater management practices are typical in New Castle County:

  1. Wet ponds
  2. Dry Ponds
  3. Bio-filtration Practices such as Bioretention Facilities and Bioswales
  4. Underground Storage Tanks
  5. Sand Filters
  6. Green Roofs, and
  7. Porous Pavement