Storm Water Conveyance

As a community continues to develop, additional demands are placed on its storm water conveyance systems. A storm water system usually has several components that can include catch basins, storm sewers, creeks, storm water detention ponds, lift stations, force mains, ditches, and drainage features to accommodate storm water runoff. Consequently, improving storm water management is frequently one of the largest undertakings a community faces.

Storm water management improvements should be comprehensive in scope and aimed at addressing aspects of not only increasing conveyance capacity, but also at reducing peak flows and total runoff.

Most communities usually address only the first aspect of storm management which is to improve conveyance. This is accomplished by installing larger pipes to increase the flow carrying capacity. Another means of improving conveyance capacity is by providing adequate maintenance (cleaning) of the various structures within the system.

There are many options to reduce peak flows and reduce total runoff, ranging from increasing vegetation (grassy areas and tree planting), reducing or eliminating impervious areas, modification to conveyance structures, and creation of detention storage. In recent years, detention storage (or detention ponds) have drawn a lot of attention due to the many advantages they propose.

Detention ponds can be either wet or dry. Wet detention ponds are storm water control structures providing both retention and treatment of contaminated storm water runoff. A detention pond consists of a permanent pool of water into which storm water runoff is directed. Runoff from each rain event is detained and treated in the pond until it is displaced by runoff from the next storm. By capturing and retaining runoff during storm events, wet detention ponds control both storm water quantity and quality. In addition, evaporation and groundwater infiltration often play a significant role in the reduction of total runoff.

Benefits of wet retention ponds include decreased potential for downstream flooding and stream bank erosion and improved water quality due to the removal of suspended solids, metals, and dissolved nutrients.

Dry retention ponds are usually design to take advantage of permeable soils to promote groundwater infiltration. However, when designing dry water ponds, water quality should be carefully addressed.

A side benefit of reducing total runoff (with either a dry or wet retention pond) is the reduction in size or even elimination of improvements to a conveyance system.

Services

Jones & Henry can assist your community in improving all aspects of a storm water drainage system including:

  • Developing a Master Plan for system improvement
  • Developing a hydrologic/hydraulic models of the system to assess system deficiency and propose improvements
  • Storm and sanitary sewer separation
  • Design of storm sewers, culverts and inlet structures
  • Design of lift stations and force mains,
  • Design of detention ponds
  • Oversight of construction

 

Jones & Henry
Engineers, Ltd.