A Study of Trash and Trash Interception Devices on the Cooks River Catchment, Sydney

A field study was carried out to determine the typical composition of trash collected by two floating booms and a trash rack in the Cooks River catchment. All of the samples consisted mainly of garden refuse, plastic and paper. The booms and rack differed in their abilities to collect different components of trash and consequently a choice of the most suitable trash interception device should be governed by the trash composition at a particular site. Increasing flows resulted in smaller quantities of trash being retained by the booms and rack investigated. Laboratory tests were carried out to investigate whether the type of rack currently being used in N.S.W. could be self-cleansing so as to avoid blocking during storms. These results showed that both the clear spacing between bars and the angle of inclination of racks investigated would not allow racks to be self-cleansing. Increasing flow velocity appeared to have a relatively minor influence on self-cleansing capacity. It appears that new types of trash rack installations are necessary for them to be self-cleansing.