Construction and Monitoring for a State of the Art Foundation Grouting Program at Rough River Dam-Paper

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Rough River Dam, a high-hazard USACE embankment dam in Kentucky, was designated an urgent safety concern because karstic bedrock beneath the dam could enable internal erosion. High reservoir events in 2007 and 2011 triggered concerning changes in instrumentation, while monitoring later confirmed strong hydraulic connections between the reservoir, foundation, and downstream stilling basin.<br /><br />From 2015 to 2017, USACE completed an exploratory and production grouting program to characterize the foundation and inform a planned cutoff wall. The work installed 328 grout holes across two partial grout lines, involving more than 39,000 linear feet of drilling and approximately 213,000 gallons of grout. Construction incorporated sonic drilling through the embankment, staged grouting, instrumented packers to measure pressure at the injection point, automated monitoring of more than 100 instruments, and electronic records and real-time data systems.<br /><br />The investigation found extensive solution features, clay-filled voids, and interconnected pathways in the Haney and Beech Creek limestones. Grout emerging in the stilling basin, rapid piezometer responses, and communication between widely separated boreholes confirmed that karst pathways connected areas beneath and across the dam, including beneath the outlet conduit. These observations established the potential for unfiltered seepage exits and continued erosion.<br /><br />Grouting reduced seepage in some areas and increased head loss across the dam foundation, but monitoring indicates that preferential flow paths remain, especially near the foundation contact and beneath the conduit. The improvement is considered temporary: another major high-pool event could increase seepage and accelerate erosion. Continued instrumentation monitoring is therefore critical until a cutoff wall is built to permanently address the foundation risk.

Keywords

Rough River Dam

USACE

karstic bedrock

internal erosion

embankment dam

grouting program

foundation seepage

cutoff wall

piezometer monitoring

solution features