Hydrodynamic Separator

The newer, more sophisticated devices, such as hydrodynamic separators, catch 100 percent of litter and organic debris. In other words, they catch everything down to a hair on your head or 50 microns, including flood-causing sediments, litter, oxygen-lowering organics like grass clippings, branches, and parking lot pollutants (i.e. oils, litter, debris). They represent hundreds of volunteers picking up litter.

Hydrodynamic separators reside below the ground and when full you call in a vacuum truck. The vacuum trucks pop the manhole cover, insert the vacuum truck hose, suck it all out, and take it to a landfill. In Pensacola, they call in the trucks a few times a year for each underground device.  If the devices are not emptied, they automatically go into bypass mode.  In Pensacola—once at the landfill--they dry it all out, separate the litter, and reuse the sediments for fill needed in other projects.  Depending on how much stormwater is treated and the kind of litter or pollution entering a watershed determines the cost of this equipment. The cost of this equipment ranges from $10,000 to $300,000. 

Band-a-Longs and Litter Traps

Band-a-longs with litter trap cages are perfect for in-stream stormwater solutions and can be placed in a dry river bed (like Ward Creek) where they will rise and fall with the water level and catch about 85-90 percent. They must be placed where there is easy access to clean them out. They range in cost from $14,000 for the smallest unit such as the Bandit and between $160,000-$300,000 for their larger band-a-long models. For the larger models, a crane is needed to lift the cage and empty the contents.

Booms

Oil booms with skirts are also used to manage stormwater debris and litter and catch about 80 percent. Once installed, they can be a challenge to access. Some are accessed by boat. Some cities build a bridge over them and hand pick from the top, while others put on chest waders and get in the water to collect the litter. Depending on access, a vacuum truck can be used to empty them.

Booms are high maintenance devices because if not cleaned out after each storm, litter merely goes under and over them. Booms are cheap to buy and install usually costing a few thousand dollars installed, and a broken boom can be replaced for under $1,000.