|Geologic features at Bonny Damsite consist of the following;|
1)Valley fill alluvium to depth of 15-20 feet, stream deposited material consisting mainly of silt, sand and gravel.
2)Valley sides of soft Ogallala sandstone encountered beneath the alluvium is a fairly impervious material, lightly cemented and fine sand in grade size.
3)A loess mantle over the high land, which varies from silt to silty fine sand.
4)Fine sand located at the right portion of the dam which overlies sand and silt of the valley fill and is in turn overlain by alluvial sand and silt.
5)Pierre shale bedrock underlies the entire region and is usually found at depths from 55 to 60 feet beneath the valley floor.
6)Talus forming a narrow strip on each side of the valley.