Fall Creek Falls State Park Dam

S&ME provided dam inspection and programmatic design and construction cost estimating for an approximate 78-feet earthen dam at Fall Creek Falls State Park.  The dam was constructed around 1969 and experienced progressive surface sloughing on the downstream slope due to a steep slope inclination of 2(Horizontal) to 1(Vertical).

Fall Creek Falls Dam was with zoned embankment construction with a central Impervious Core fill and exterior Common Fill material.  The Impervious Core fill was specified to be compacted to 95 percent standard Proctor with the Common Fill was specified at 90 relative compaction and experienced surface sloughing.

S&ME performed topographic survey and bathymetric studies for the dam area. A geophysical survey of the dam site was performed for the downstream dam area including spontaneous potential (SP) and frequency domain electromagnetics (FDEM).  A natural resources jurisdictional study was performed in the dam area.  A CCTV camera study was performed to evaluate the interior condition of the service spillway 48-inch outlet culvert.

S&ME performed a subsurface exploration for the dam including fifteen soil test borings and six piezometers.  The soil test borings included SPT testing and sampling and undisturbed sampling. Laboratory testing including triaxial shear and soil index testing were performed to estimate engineering properties of the zoned embankment materials.   Hand auger borings and test pit excavations were also performed along the downstream slope to evaluate near surface soil conditions.

Slope stability analysis was performed using subsurface soil and water level data and laboratory test data from the exploration using Slope/W.  The stability analysis included steady-seepage, rapid-drawdown, and seismic analysis.

Our teams also developed repair plans for the dam that include excavation of the sloughed soil materials, construction of a weighted filter overlay/rockfill berm on the downstream slope, and modifications to the 48-inch diameter service spillway culvert outlet.  The embankment repairs were designed and permitted through TN Safe Dams. A revised dam breach and inundation study for the dam using HEC-RAS was also prepared for submission to TN Safe Dams.