Retention/Detention Ponds

Practical Solution

The “How To”

Creation of a retention or detention pond should be undertaken only after careful consideration of the current status and future needs of the area. These ponds take up space and require regular maintenance. It is also important to note that retention ponds must be designed to keep people from trying to enter the pond area.

There are many resources available to assist in designing and maintaining retention/detention ponds. The US EPA's Storm Water Technology Fact Sheet: Wet Detention Ponds provides a good overview of detention ponds, as well as a section on advantages/disadvantages. The authors point out that the benefits far outweigh the disadvantages in most cases. The US EPA's Stormwater Best Management Practice Design Guide provides information about where retention and detention ponds are most appropriate, design criteria, and maintenance. An article on best practices for water management from the Missouri Office of Administration provides information on various kinds of retention/detention ponds, including detention ponds (p. 1), extended detention ponds (p. 9), infiltration basins (p. 17) and infiltration trenches (p. 25). The Missouri Botanical Garden also offers guidance on Design and Plant Selection for Bio Retention Facilities.

Once the ponds are built, they require regular maintenance. This article on Maintaining Detention Ponds provides a good overview. The City of Wentzville also published a Citizen’s Guide for retention/detention pond maintenance.

Dollars & Cents

The formula below was calculated by a study (Brown and Schueler, 1997) which is promoted by the EPA as the construction costs formula for retention ponds.

C = 24.5V^0.705

where:

C = Construction, design and permitting cost;

V = Volume in the pond to include the 10-year storm (ft³).

 

Using this equation, typical construction costs are:

$45,700 for a 1 acre-foot facility

$232,000 for a 10 acre-foot facility

$1,170,000 for a 100 acre-foot facility

Measuring Success

The Recarga Model is an excellent resource. This model is used to evaluate the performance of bioretention facilities, rain gardens, and infiltration basins. Communities can use this tool to evaluate the performance of a new retention or detention pond. The Metropolitan St. Louis Sewer District (MSD) uses the Recarga Model and other performance measures to evaluate stormwater management practices. These other performance measures include the EPA's SWMM tool and other measures developed by MSD.

OneSTL's Water Quality performance measure will also be an indicator of how successful retention and detention pond projects are. This is a measure of the impaired (polluted) rivers and streams in the region, and the desired trend is downward.