Catch basins can be cleaned out by hand, but a eductor truck (commonly referred to using the brand name Vactor) is more commonly used. The eductor truck uses hydrodynamic pressure and a vacuum, to loosen and removes solids and standing liquids (typically liquid remaining in the sump of the stormwater facility from preceding precipitation events) from a catch basin or other stormwater facility. The waste is carried in a tank mounted on the truck and the entire load is dumped at a central site. This system has a problem in that it creates a large amount of liquid in comparison with solids. The liquids are difficult to transport and places to properly dump the liquids are difficult to find.
Street sweepers are used to remove litter, debris, and fines from street and parking lot surfaces. Street sweeping systems vary from mechanical broom sweepers, to vacuum/brooms, to regenerative air systems. Street sweeping is good method and necessary method for removing litter and other coarse street waste. However, its usefulness is limited by access, slope, and wet weather and difficulties in removing the finer and more contaminated particles. Better removal of the finer particles may be accomplished using regenerative air systems in conjunction with the broom or broom/vacuum systems.
Current street waste disposal and utilization practices are extremely varied. Solid disposal and/or use varies from landfill disposal, asphalt and concrete manufacture, hazardous waste treatment, reuse, fill and dumping in pits. Some of these methods are not appropriate.
Liquid disposal is also varied. For example, some communities decant liquids into sumps to separate liquids from the solids. Liquids settle anywhere from two hours to overnight. Liquids overflow into the sanitary sewer when more liquids are added and solids are removed about every other day. At other locations; solids and liquids are dumped into a holding bay where liquids run off, drain into settling tanks and then are discharged into the sanitary sewer. Unfortunately, dumping in pits and letting the liquid run off is also used for liquid and solid disposal.
The Thurston County regional decant facility received 340 cubic yards of catch basin solids from Olympia, Lacey, Tumwater, and Thurston County government in 1994 (Meyer, 1995). A survey by Snohomish County Department of Public Works (1994) estimated government agency street grit collection for the Snohomish County area at 4,540 tons (3,500 cubic yards). The Snohomish County survey also shows the extreme variations in the amount of street waste collected in a year in that the Everett estimate was 12 pounds per resident while the Edmonds estimate was 75 pounds per resident.
In Alameda County, California, the amount of street sweepings collected per mile ranged from 1.4 to 2.0 cubic yards (Alameda County, 1993).
Eductor truck operators typically decant liquids in the field before going to special site to dump solids. With less water, trucks are safer to operate, load limit problems less, and more solids can be hauled. The average truck decants three times a day with approximately 1200 gallons per decant (Herrera, 1991). Liquids are decanted back into the cleaned catch basin, storm sewer, sanitary sewer, or into surface water.
© 2005 World Sweeper