| The Heart River has incised about 125 feet into the gently rolling prairie topography and the Heart Butte Dam has been place in a relatively narrow constriction of the river. Rock at the dam and appurtenances is predominantly fine-grained, light gray sandstone of the Ft. Union Formation, containing hard, concretionary strata near the abutment crests and a series if interbedded shales in the exposed section beneath the dam. The orientation of bedding planes is nearly horizontal and the rock is slightly to moderately jointed. Alluvium in the river valley ranges from a few feet to about thirty feet in thickness. |
