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Wolf Creek Dam project is right on schedule


By BILL MARDIS, Someret Commonwealth Journal

A construction update this week from Wolf Creek Dam indicates rehabilitation of the mile-long structure is on schedule and progressing as planned for completion in three years.

Allison Jarrett, public affairs specialist for the U.S. Army Corps of Engineers, said Treviicos Soletanche JV, general contractor for the project, has completed installation of the last panels of the protective concrete embankment wall in Technique Areas 1 and 2. The two technique areas are test spots to confirm integrity of the process to stop uncontrolled seepage through the dam that has been declared in high risk of failure.

The protective concrete embankment wall in its entirety consists of 427 concrete panels, 6 feet wide and 10 feet long, to stabilize the earthen section of the dam while a permanent barrier wall is installed.

The protective concrete embankment wall will extend from the work platform on the upstream side of the dam downward to the base of the earthen section. This wall, as well as an original wall installed in the 1970s, will remain in the dam to augment the permanent barrier wall that will extend as much as 100 feet into the bedrock below the dam. The permanent wall is scheduled for completion in October 2012.

The original wall, installed after more serious leaks developed in the dam during the late 1960s, was not long enough or deep enough to permanently repair the dam. The first wall extended only about 25 feet into the bedrock below the dam and stopped short of protecting the entire length of the structure. Seepage increased to the point that an outside panel of experts declared the structure in high risk of failure. The Corps announced publicly in August 2005 that a major rehabilitation of the dam was necessary.

Jarrett said this week that subcontractor Hayward Baker has grouted 100 primary and secondary holes along the right rim near Halcomb’s Landing. Testing results indicate 94 tertiary (third) holes will be required to meet closure criteria (about 75 percent of these tertiaries are completed). She said Hayward Baker has completed grouting large cavities in Critical Area 1 and has begun grouting the rock beneath.

A really troublesome spot is Critical Area 1 near where the earthen and concrete sections of the dam join. Original efforts to pump high-mobility (thin) grout into the critical area increased seepage and there was indication of material movement inside the dam.

Grouting was halted, resulting in an incomplete grout curtain to temporarily control seepage. The problem delayed any consideration of raising the lake level until October 2010, meaning the lake will remain at its current level through next summer.

CLIC