Stormwater Detention Basin Retrofit
St. James Church and School, Great Swamp, NJ
F. X. Browne, Inc. designed a stormwater wetland retrofit project for an existing dry detention basin at a church in the Great Swamp Watershed in New Jersey. The detention basin was converted to a pond-wetland system to provide water quantity and water quality benefits.
The existing basin provided stormwater storage for flood control but did not provide water quality treatment of stormwater, particularly for smaller storms. The retrofit design deepened the basin to add a forebay for sediment removal and equalization. The low flow channel was removed from the basin and the remainder of the basin was recontoured to create a meandering path from inlet to outlet. Plants were hand-selected for different parts of the basin based on water depth and location. The stormwater wetland provides water quality treatment of stormwater in addition to the flood storage for which it was originally designed. Water quality monitoring was performed to evaluate the pollutant removal efficiency of the retrofitted basin.