Progress on the concrete plinth of the main dam in recent months has made the 18-inch-thick, 36-foot-wide slab one of the most prominent fixtures of the Chimney Hollow Reservoir construction site. Now at about 30 percent complete, the plinth will eventually stretch across much of the valley to help provide a solid base along the entirety of the almost 3/4-mile long dam.   

The plinth is the piece of the main dam that will tie together the above-ground elements of the dam to the subsurface portions, providing a watertight connection between the dam’s 350-foot-tall asphalt core and the grout curtain that will run as deep as 235 feet below the foundation. 

To help provide a structurally sound base for the main dam, the plinth is made up of rock anchors, steel pipes are placed through the rebar to provide a conduit for grouting and concrete poured on top in 20-foot sections. A heat-resistant water stop, specially ordered from Germany, is embedded between the plinth sections and will also be embedded in the asphalt core to make the entire plinth water tight.