Let’s first, in its simplest terms, define what it means for something to be temporary or permanent. Temporary is something that is only to last for a short period of time and then possibly will no longer be needed for its initial purpose. Permanent is something that is expected to stay in place to provide long term stability or is required for functional soundness.
A temporary basin best management practice (BMP) is structurally designed settling pond to slowly capture stormwater runoff. The primary objective is to detain stormwater for a short period time, and through a slow-release mechanism such as a baffle allowing sediment to filter out. These types of temporary structures typically have a useful life of approximately 18 months or until the construction is completed and the final stabilization phase is taking place.
According to the Florida Department of Environmental Protection (FDEP)’s Construction Generic Permit (CGP), temporary drainage basins are required for construction sites that are 10 acres or more. Additionally, a temporary sediment basin must provide adequate storage based on construction area size, embankment stabilization controls, and stormwater velocity dissipation measures.
To improve the effectiveness of a temporary sediment basin, it should be located to catch the largest possible amount of stormwater runoff from the disturbed construction area. Placing this effective BMP at a low-lying area where natural drainage can take place is a critical step to increase the structure’s effectiveness.
Temporary sediment basins may be designed to become permanent structures after construction is completed. Whenever these structures are to become permanent, they must be designed as permanent ponds by a qualified professional engineer. Permanent ponds are beyond the scope of a temporary Basin BMP.
Permanent sediment pond structures are defined as detention or retention ponds. Detention ponds and retention ponds are excellent structures to consider for permanent stormwater runoff controls. However, space is a critical factor and must be seriously consideration prior to construction if they are required based on the landscape.
Retention ponds are sometimes called dry ponds therefore are usually dry except during or after rain event. The objective is to slow down stormwater, hold it, and establish the ability to store the water and allow it to dissipate. A detention pond is an area where stormwater is temporarily stored, or detained, and is eventually allowed to drain slowly into local receiving waters.
Temporary or permanent sediment basins, especially during construction, are expected to be inspected on a routine basis and after a rain event causing stormwater runoff to occur on the site. The primary objective for all inspections is to review and determine any maintenance that may be required to ensure sediment accumulation remains below 50 percent.
Site developers and contractors must successfully integrate a storm drain system and sediment controls into their site designs and plans. KCI is here to help. Call us today at 888-346-7779.
