Washed Up Materials

Storm sewer systems carry a great amount of solid mate­rials that discharge directly to receiving waters. Much of this material does not sink when discharged, but is able to float and accumulate on the banks of rivers and streams and tends to wash up on shorelines and public beaches. Depending on the impact these materials have on the area in which they have been discharged, recreational and/or commercial activities such as swimming or fishing may be banned.

One of the NPDES requirements for CSO dischargers is the control of floatable material. The purpose of this requirement is to assure that the CSO discharger is aware of the high public visibility and aesthetic impact that solid and floatable material can have on the com­munity. Although the most visible impact may be aes­thetic, public health concerns are significant because ability of medically-related items such as syringes to be discharged through CSOs.

In the past, many communities trying to control their float­able discharges have constructed catchments upstream of their CSO discharge points. The catchments could be as simple as a bar screen or simple trash rack, or as complicat­ed as a regulator chamber with removable netting. The idea is that solids and floatable materials would he trapped in these structures while allowing stormwater to be dis­charged. At some point a maintenance crew would come and collect the solids and floatables and dispose of them properly.

Problems arise when inflow occurs at the unprotected stormwater outfall or at the outfalls where faulty flapgates are present. Rising waters can travel back upstream into the catchments entraining the solids and floatables the system was designed to trap. Many times these solids would lodge in upstream piping, causing pipe blockage and reduced flow capacity.

Tideflex Check Valves, combined with mechanical solids/floatables collection systems, provide a cost-effective and regulatory compliant solids/floatables control strategy. The Tideflex Check Valves offer excellent backflow prevention under the harshest conditions, ensuring that backflow will not wash collected floatable debris out of catchments, racks or screens.