being 70 top soil in one particular instance 70 wood or 70 rock in others the apparatus discharges separated streams of fine product 3 like top soil high density product 4 like metals or rock low density product 5 like wood and oversize rejects 6 the trailer 1 comprises a structural frame 7 for supporting and mounting a disc screening assembly 8 rotary screen or trommel 9 an air separation device 10 and transport rear wheels 11 the trailer configuration is convenient for permitting ease of transport from site to site a portable generator set 12 is provided to power electric drives and controls the frame 7 incorporates jacking means 100 near the front and rear for levelling the equipment a metered feed hopper 13 and elevating conveyor 14 is used to deliver the aggregate 2 at a nominal 150 cubic yards hour to the top of the trailer 1 a short horizontal feed conveyor 15 positioned at the front and top of the trailer 1 directs the aggregate 2 to the disc screening assembly 8 the disc screening assembly 8 is a horizontal linearly aligned array of progressively increasing particle sizing sections four 4 39 wide sections 16 17 18 19 are provided passing particles possessing dimensions of less than.