Pressure Grouting – A Multipurpose Solution for Dam Rehabilitation

Grout curtains continue to gain popularity as both an effective short-term, and a durable long term option for reducing seepage through fractured bedrock dam foundations. Similar pressure grouting techniques can be considered to address other dam rehabilitation needs as well. This paper will discuss the means and methods that were successfully used to install a grout curtain in the fractured bedrock foundation, and address defects in overburden soils using advanced pressure grouting techniques at the Lockington Dam in Piqua, Ohio. This information should be of value to
owner/operators of similar problematic dam structures that may be evaluating pressure grouting as a means of improving overall seepage control.
Completed in 1921, the Lockington Dam stands 69-feet tall, 409-feet wide at the base and is comprised of 1.135 million cubic yards of earth with a concrete spillway structure containing two concrete drainage conduits. The dam manages a drainage area of approximately 255 square miles.
In 1999 the Miami Conservation District (MCD) launched a Dam Safety Initiative to address potential weaknesses in the existing flood protection system. Underseepage at Lockington Dam was identified as a primary issue. As a result of the hydraulic placement methods of the earthen fill during construction, some glacial outwash material was incorporated into the Dam embankment at the abutments. This material was found to contain well-graded sands, cobbles and boulders, also identified as a potential pathway for water seepage through the embankment.
Geo-Con, a trade name of Environmental Barrier Company, LLC., a specialty Geotechnical Contractor, was contracted by MCD to work with MWH Americas to install a grout curtain, intended to reduce seepage through the underlying fractured bedrock. Pressure grouting was also specified for use in the glacial outwash material overlying the bedrock. Both applications were to be completed using advanced grouting methods, including the use of balanced/stable grouts and real-time computer monitoring of the grouting parameters. The work began in May of 2010, and was successfully completed in November of the same year. This paper will detail key components of the grouting program as well as means and methods used to install the grout curtain and performance of the pressure grouting.