V. Large‐Scale Stormwater Management

 

V. Large‐Scale Stormwater Management

The following section outlines a few large‐scale stormwater management practices. These practices require some degree of engineering, and are usually implemented for city stormwater management because of the need to manage large volumes of runoff. However, the enthusiastic community stormwater steward may find an interest in some of these applications, especially those who manage large properties, such as farmers. This section provides a brief definition of each device with some resources for further information.

  • Stormwater Planter
  • Stormwater planters are small‐scale detention devices composed of planter boxes, soil and plants. They provide stormwater detention and treatment through filtration and biological processes. There are several types of advanced stormwater planters

Flow‐through Planter: Flow‐through planters have impervious bottoms (they do not infiltrate to provide groundwater recharge. These devices can be set at or below the ground surface and are generally waterproof. They are composed of a basin within stormwater inlets, gravel or soil, and planted vegetation. The stormwater drains into the planter, filters through the media and plants, and then is drained to an outflow via a perforated drainage pipe at the bottom of the planter. The main function is to treat polluted runoff.

Infiltration Planter: Infiltration planters are very similar to flow‐through planters in design and function. The difference being that infiltration planters infiltrate the inflowing stormwater. Rather than having an impervious bottom, the bottom of an infiltration planter is composed of pervious soil. When the inflow of stormwater runoff enters the system, it infiltrates down through the plants and soil before percolating deeper into the surrounding soil.

  • Wet Ponds
  • Wet ponds are permanent pools of standing water that promote gravitational settling and biological remediation of particles and pollutants. They provide a buffer to further suspension of pollutants during new storms, while providing displacement of some of the settled water. Detention time can last anywhere from weeks to months

 

  • Constructed Wetlands
  • Constructed Wetlands are artificially created wetlands that replicate the natural process of stormwater infiltration and treatment. They are shallowly constructed depressions, often no more than a single foot deep. They provide excellent pollutant removal through slow infiltration and through biological and microbial decomposition and uptake.