A depression designed to hold stormwater for 24 - 72 hours in order to allow sediment and pollutants to settle before the water drains. According to Fairfax County, dryponds planted with wetland plants and that support wetlands species perform better than those planted with lawn grass.
Of the man made ponds designed exclusively for stormwater management, dry ponds are probably the simplest to design, thus most common. They are designed only to settle out coarse particles of sediment and have no permanent pool. Lawn grass may be a poor choice for vegetation simply because it may not survive occasional inundation.
According to the U.S. EPA, typical pollutant rates are:

Total Suspended Solids	61%
Total Phosphorous	19%
Total Nitrogen	31%
Nitrate Nitrogen	9%
Metals	26% - 54%

AKA

extended detention basins, detention ponds, extended detention ponds

PERFORMANCE CRITERIA

Water quality of water exiting drypond.

ILLUSTRATION



CASE STUDIES
Mill Creek Canyon Earthworks Park, Kent

ADDITIONAL RESOURCES

Fairfax County Fact Sheet:http://www.fairfaxcounty.gov/dpwes/environmental/swm_quickref.htm

StormwaterCenter.net Fact Sheet:http://www.stormwatercenter.net/Assorted%20Fact%20Sheets/Tool6_Stormwater_Practices/Pond/Dry%20ED%20Pond.htm