Backhoe dredges are stationary tools, with three paddles. Two of the paddles are fixed (starboard and portside), while the third paddle is moveable (backside of the pontoon).
There are two types of hydraulic dredgers: backhoes and dipper/front shovels. A backhoe is the most common type. They differ in how they work. To dredge the bottom of the lake, the backhoe pulls the bucket while the shovel pushes it. Typically, the last method is used only when the water depth is insufficient for the pontoon.
Due to the anchoring by spud poles and the fixed boom and stick the dredging depth is limited.
Some of these types of dredgers are self-propelled.
In 1999, the biggest backhoe dredger in the world was delivered by Shipyard "De Donge" to "Great Lakes Dredge & Dock Co". This dredger is equipped with a Liebherr P996 excavator and can dredge with a 13 m' bucket till approx. 17 m. depth. The dredge can however edge to a maximum depth of 30 m. in case the boom 1 stick configuration is changed. The maximum penetration/ breakout capacity is 170 tons! The weight of the excavator is 470 tons!
