Abstract: A dam of earth or rock fill is provided with an impervious core by forming a trench near the center of the fill and sequentially building plate-shaped wall sections in the trench from poured soil-cement mixture. The wall sections which are superimposed on each other in edge-to-edge relationship are hingedly connected by joint assemblies of tough, yieldable material, such as soil-cement enriched with bentonite.

Abstract: An earth basin of a waste water clarification plant is divided by two concentric, cylindrical partitions into a central, circular, settling area to which the waste water is fed from an inlet, a circularly annular activating area surrounding the settling area and connected therewith by an overflow, and a final clarification area surrounding the outer partition and extending therefrom to the oval embankment of the basin which extends in a concentric semi-circle 180.degree. about the common axis of the partitions, but is elongated radially over the remainder of the basin circumference.