Wet Pond Design Without Visible Forebays to Reduce Cost of Operation and Maintenance and Use of Forebay Space for Other Purposes

Saifuddin Ahmed, TX, PE CFM LEED AP

Stormwater wet ponds serve mainly two purposes – by temporarily detaining flood peaks for a pre-determined period and then release the runoff slowly at a prescribed rate and lower velocity and by treating runoff by settling impure particles present in influent stormwater to the pond forebay so that treated and clean stormwater is released out of the pond. Traditional designs show forebay as a visible separate compartment in wet ponds. The main functions of forebay are to settle and retain impure particles present in runoff as a result of reduction of velocity in it and to control odor produced by sediments in its deeper portion as it is dug about 6’ to 9’ below pond inlet pipes. The forebay is cleaned every few years by dredging and moving out settled sediments to reclaim the volume lost to sediment deposition to sustain its intended function of removal of polluted particles present in storm runoff and this maintenance operation became costly for some jurisdictions.