The Downstream Defender is designed to remove settleable solids, floatables, and oil from stormwater runoff. Because sediment and oil storage areas are outside the main flow path through the unit, previously collected solids, oil and floatables are not washed out (re-entrained) in the effluent during major storm events or surcharge conditions. In addition, with proper maintenance, treatment capacities are not reduced as pollutants accumulate between clean-outs.

The chart below shows the peak treatment flow rates for standard sized Downstream Defender units. Custom sized units can be provided under special circumstances. The bulk of pollutant material tends to be included in the 'first flush' of the runoff during a storm event, as the flow rates build up, therefore with a correctly sized unit, the vast majority of solids and hydrocarbons can be removed within the unit.

Notes:

1. Peak Treatment Flow rate is based on keeping headloss at a minimum and removal efficiencies within a desirable range. Higher flow rates are possible if lower removal efficiencies and higher headlosses are acceptable.
2. Headloss is defined as the difference between the top water level upstream and the top water level downstream of the unit.
   • AutoCAD drawings and Microsoft Word specifications available on disk.
   • For pricing, delivery, and custom design, please call Hydro International's Contracts Department.