ABSTRACT: This report summarizes regional geologic data pertinent to construction of a dam and reservoir on the Patoka River near Ellsworth, eastern Dubois County, Ind. The river occupies a valley that in its lower (western) reaches is broad by comparison with most valleys in the dissected upland area through which the river flows. The broad valley is underlain by alluvial and lacustrine deposits that in the vicinity of the damsite are 50 to 80 feet thick. This stage of valley filling was caused by blocking of the mouth of the old upper Patoka valley by glacial and glaciofluvial deposits. Bedrock in the area includes one group of formations of Pennsylvanian age and four groups of Mississippian age. The Pennsylvanian rocks are principally sandstones and shales; Mississippian rocks include approximately equal amounts of sandstones, shales and limestones. A disconformity separates Pennsylvanian from Mississippian rocks, and all of these formations dip almost due west at about 25 feet per mile. The only serious geologic problems involved in construction of a dam and reservoir at Ellsworth are centered around the damsite. Two beds of cavernous limestone, 14 feet and 30 feet thick, occur in the valley walls at the damsite and in adjacent parts of the reservoir area. Detailed engineering studies must be made to determine the extent and nature of the treatment that will be necessary to prevent serious leakage through these limestones. Other engineering studies will be needed to determine the bearing capacities of the thick valley fill and the suitability of available unconsolidated deposits for earth-fill in the dam. Limestone for rockfill and concrete aggregate is in adequate supply. The flood pool should not be raised above the proposed 550-foot altitude to avoid seriously increasing leakage and bearing problems.
Gray, H. H. 1963, Geology of the upper Patoka drainage basin: Indiana Geological Survey Special Report 02, 23 p., 6 fig.
You may also like:
Can't find what you're looking for? Feel free to contact us directly:
Publication Sales Office
Indiana Geological and Water Survey
420 N. Walnut St.
Bloomington, IN 47404
IGS Return Policy
All sales are final. Materials may not be returned after they have been accepted by the customer. Any discrepencies in mail orders must be reported to IGWS within 10 days of receipt of order.
The Indiana Geological and Water Survey will refund the purchase price and sales tax of products if returned with the original sales receipt within 10 days of receipt of order. Refunds will be issued with the same method of payment as indicated on the original receipt except for cash purchases, which will be refunded by check. Items must be returned in the same condition as purchased. Refunds on digital products and services are not allowed, except for defective media such as CD-ROMs, flash drives, and so on. The customer is responsible for paying shipping costs to return items.