Abstract: A system for transportation of sludge material comprising an elongated tank having an arcuate bottom portion extending longitudinally of the tank and having a withdrawal port located in the arcuate bottom portion of the tank. An elongated conveyor system is disposed in the tank and comprises inner and outer auger flights mounted in the tank an axle extending longitudinally of the tank. The auger flights transcend only a minor cross sectional area of the tank and are configured to have opposing pitch slopes. The outer auger flight provides a positive pitch angle in the direction of the withdrawal port to displace sludge material toward the withdrawal port. The compound conveyor system embodies inner and outer auger flights as described previously in which at least the outer auger flight is in the form of a ribbon which is spaced axially from the axle on which it is supported and is wrapped around the axle in a manner in which the inner diameter of the ribbon flight is spaced radially from the axle.