FOR IMMEDIATE RELEASE                                      Contact:  Jeff Hawk, 412-395-7501
Release No. 08-355                                                      CELRP-PA@usace.army.mil      
December 30, 2008                                                       Mobile: 412-526-5426

Army Corps stabilizes failing Allegheny River navigation dam
More work required to complete scour repair project

PITTSBURGH -- The U.S. Army Corps of Engineers, Pittsburgh, announced today that efforts to stabilize a failing navigation dam on the Allegheny River near Clinton, Pa., have succeeded. The Army Corps initiated an emergency repair contract in early November after divers discovered severe scour conditions underneath Allegheny River Lock and Dam No. 6 during an inspection. The Corps’ contractor, Brayman Construction Corporation, mobilized to the site soon after the discovery and began placing concrete into a large void extending nearly 200 ft along the length of the thousand-foot-long dam, up to 20 ft deep, and about two-thirds of the way underneath the dam.

The Army Corps deemed the dam unstable and took measures to ensure it was operated safely while crews repaired the damage. Officials were concerned that ice loads on the dam or large chunks of ice slamming into the dam could knock it off its exposed wood piling foundation and into the river.

Brayman Construction crews first installed a steel wall along the toe of the dam to seal off the void and then filled it with sixty truckloads of concrete designed for underwater placement. 

“We were able to place 600 cubic yards of concrete into the void to stabilize the dam while we had low flows in the river,” said Brian Greene, project manager for the Corps. River flows have remained too high the past two weeks to complete the project, which entails filling a few smaller voids and placing rock along the downstream portion of the dam to prevent further erosion. Workers have also installed foot-high wood panels called “flash boards” on top of the dam, which divert water away from the work area.

Army Corps officials report that while more work is required to complete the project, critical repairs needed to shore up the dam has been completed.

“We’re constantly monitoring the river conditions and looking for an opportunity to finish the project when flows are low enough to do the work safely,” added Greene. “We have about a week’s worth of work remaining.”

Rain and melting snow have created high flows on the river that are three times the level needed for crews to safely complete repairs to the 80-year-old structure. The contractor has staged a high-speed drill rig on site and materials nearby so that the crews can react quickly to a favorable change in the river conditions.

An inspection of the remaining seven Allegheny River lock and dam facilities did not reveal severe erosion problems at other structures, though Allegheny River Lock and Dam No. 5 shows similar, less severe erosion that will require some repair work.

Pittsburgh District officials say that age, fatigue and the deteriorating condition of the region’s navigation system coupled with hundreds of millions of dollars of unfunded critical maintenance work on the Allegheny, Monongahela, and Upper Ohio Rivers will probably result in additional unplanned repairs.

“We’re in fix-as-fails mode,” said Colonel Michael Crall, district engineer for the Corps in Pittsburgh. “We’re making critical repairs that threaten the reliability of the system and trying to slow the increasing number of unscheduled breakdowns,” he added.

Crall applauded the engagement and coordination of local stakeholders during the repair effort, including Sithe Energies, which owns and operates the hydropower station on the dam and is adjacent to the work site. During the repairs, Sithe Energies drew as much water as possible through its hydroelectric plant to reduce flows over the dam and to facilitate lower flow conditions for construction crews. The United States Coast Guard’s Marine Safety Unit Pittsburgh assisted by placing warning buoys around the work site to alert commercial vessels and recreational boaters.

The quick response may have spared the region from several serious impacts had the dam failed. A loss of the pool would have shut down commercial and recreational navigation on the river. Severe water quality degradation for the first week would have impacted water intakes and sanitary facilities. The hydropower facility located at the dam would have suffered severe damage and ceased operations. One of the largest wetlands in the region -- the Cogley’s Island Complex downstream of Kittanning, Pa. -- would have dried up and federally listed mussel species would have been negatively impacted.

Jeff Hawk
Public Affairs Officer
US Army Corps of Engineers, Pittsburgh
1000 Liberty Ave, 22nd Floor
Pittsburgh, PA  15222-4186
412-395-7501 (Office)
412-526-5435 (Mobile)
412-395-7503 (Fax)