Preliminary Engineering Geology Report of Dam Sites on the East Fork of the Muscatatuck River in Scott, Jennings, and Jefferson Counties, Indiana

Abstract

Preliminary engineering geology investigations have been made of four proposed dam sites and their reservoir areas in the valley of the East Fork of the Muscatatuck River and its tributaries, Big Camp and Big Graham Creeks, in northern Scott County, southern Jennings County, and western Jefferson County, Ind. In this report the geologic column of the area has been divided, according to engineering characteristics, into five units. The bedrock consists of (in ascending order) unit 1, the Osgood Formation and the Laurel Limestone of Silurian age; unit 2, the Waldron Shale and the Louisville Limestone of Silurian age and the Geneva Dolomite and the Jeffersonville Limestone of Devonian age; unit 3~ the North Vernon Limestone of Devonian age; and unit 4~ the Devonian portion of the New Albany Shale. These rocks are overlain at most places by unit 5, the unconsolidated materials that range in character from red residual limestone soils to glacial till. The bedrock formations stratigraphically below the North Vernon Limestone (units 1 and 2) are essentially sound rock and offer few problems to dam and reservoir construction except the possibility of a small amount of leakage. The Jeffersonville Limestone (the top formation of unit 2) includes a gray limestone bed that contains a few solution channels, but otherwise it is sound rock. Most of the solution channels and sinkholes in the area have been formed in the North Vernon Limestone (unit 3), and serious leakage from the reservoir probably would occur through this formation if it were not extensively grouted. The New Albany Shale (unit 4) weathers quickly where it is exposed at the surface, and spillways on the New Albany Shale must be designed to prevent the rapid erosion of the shale under the attack of running water. The red residual limestone soils (of unit 5) have high liquid limits, but these materials would make a satisfactory impermeable clay core of an earth dam. The other unconsolidated materials (glacial till, outwash silt and sand, and loess) overlying the bedrock are thin but sufficient in quantity to provide fill material for earth dams. Quarries could be opened in the limestone formations at any of the dam sites to supply concrete aggregate and fill material.