Rehabilitation of Buckeye Lake Dam in central Ohio presented significant logistical and technical challenges given the history of the site, limited access and the proximity of private residences to the work. Covering almost 200 years, Buckeye Lake has a rich and varied history of industry and recreation. Presently a State Park administered under the Ohio Department of Natural Resources, the seepage, stability and hydraulic performance of the existing embankment dam was deemed unacceptable necessitating rehabilitation of the structure. Flanked by private residential and commercial properties at the downstream dam crest, construction of the new seepage barrier and new dam necessitated selection of appropriate construction methods and close coordination with the public. After presenting a brief history of the site, this paper focuses primarily on the different deep soil mixing methods utilized to construct the seepage barrier as well as the use of additional deep soil mixing downstream of the seepage barrier to construct a composite gravity dam structure.

According to the USACE National Inventory of Dams, there are nearly 84,000 dams in the United States. More than 30% of these are Significant or High Hazard, and nearly 50% are more than 50 years old. The USACE estimates that the total cost for needed dam repairs in the US exceeds $50 Billion, with $16 Billion needed for high hazard dams. More than 83% of the dams in the US are earthen embankments. One of the most serious and unacceptable performance problems for embankment dams is excessive seepage. An earthen dam with seepage problems will most likely have experienced some type of damage to the embankment or soil rock interface. Rehabilitating dams with seepage deficiencies often requires drilling through the dam and into the rock foundation for the purpose of constructing a grouted cutoff. Grouting of a rock foundation requires that multiple items of equipment be tripped in and out of a hole multiple times. For this reason, it is common that a hole is cased through the embankment with standpipe and the overburden drill tooling removed. Creating penetrations through an earthen dam and into the foundation has the potential to create hydraulic interconnections that did not exist previously and can result in dam safety concerns. Given that the casings remain in place, proper sealing of the casing annulus is crucial to the long term integrity of the dam. Grouting operations result in significant hydraulic pressures being applied and the sequence of grouting operations and predominant orientation of the rock joints must also be considered to maximize the protection afforded to the embankment.

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