Seepage Remediation at Patoka Lake, Indiana

Patoka Lake, constructed in the mid 1970s, required extensive foundation treatment to minimize leakage through highly solutioned limestone foundations. Treatments included both grouting and the construction of a concrete cutoffwall; however minimal foundation treatment was performed in an area now experiencing sinkhole development and leakage.

High (record) rainfalls in the Spring of 1996 forced reservoir waters into the spillway entrance where it remained for an extended amount of time. This resulted in the development of sinkholes and the subsequent reservoir leakage from the spillway to the Robert Hall Cave emergent downstream of the project. Consequently, the discharge at the Robert Hall weir experienced an increase from a normal 40 gpm to an estimated 4000 gpm. Total reservoir leakage was minimized by emergency sandbagging and filling of the sinkholes. Subsequent geotechnical and geophysical investigations were conducted to determine the most prudent temporary and permanent methods of repair. The investigations in the area of minimal foundation treatment have documented localized zones where the limestone section has undergone complete solutioning; therefore, without corrective action, the potential exists for loss of reservoir to approximately 30 feet below seasonal pool. A temporary levee has been constructed across the spillway entrance to provide an effective, cost efficient means to minimize further sinkhole development in the spillway floor until the design and construction of a sufficient cutoff is in place. 12 pp., 2 references.