Leader Times
29 October 2008
By Tribune Review News Service
BETHEL — Emergency repairs needed to prevent a possible collapse at Lock and Dam No. 6 along the Allegheny River could be finished by year’s end.
"We are very concerned that ice collecting on the dam or large chunks of ice slamming into the dam may cause it to fail," said Army Corps of Engineers Col. Michael Crall in a statement. Crall is the Corps’ district engineer based in Pittsburgh.
"We are taking immediate actions to address the high risk of failure at the dam before winter arrives," Crall said.
As a precaution, the Army Corps of Engineers is inspecting the remaining seven Allegheny River dams.
Dam No. 6 spans the river between Bethel Township and the Clinton section of South Buffalo.
The repairs are being made after an inspection two weeks ago uncovered more undermining than expected at the bottom of the dam.
Jeffrey Hawk, spokesman for the Army Corps of Engineers, emphasized that there is no threat to people living along the river downstream of the dam.
"There are consequences," Hawk said of a possible dam collapse. "They are serious, but they are not lifethreatening. You’d have to be in the river or on the dam. That’s the most dangerous place to be if this dam were to go."
"We don’t expect it (river) to spill over the banks and cause flooding in local communities," he said.
Mike Ferris, who lives along the river a few miles downriver from Lock and Dam No. 6 is a member of three organizations that advocate for improvements to the lock and dam system.
He agrees with the Army Corps’ assessment.
Ferris said he doesn’t believe there is an imminent threat, but adds, "Do I think that it needs to be repaired by winter? No question."
Hawk said contractors visited the facility north of Freeport on Tuesday. At least six indicated they will bid on the repairs.
"We hope to … have the fix in place by the end of the year," Hawk said.
Environmental impact
Hawk said the effect of the repair operation would be similar to when a lock and dam is taken out of operation for maintenance.
In such cases, there is no control of the pool behind it, resulting in higher flow if there is rain or excessive runoff upstream.
He said those incidences often happen without causing problems.
Hawk said if the dam were to fail, most of the immediate impact would be environmental. Mussels on protected federal lists could be harmed. There would be declines in river water quality and quantity.
That would affect one of the largest wetlands in the region — the Cogleys Island Complex downstream of Kittanning.
"A dam failure would drain Pool 6 downriver of Lock and Dam No. 7, which could leave water intakes high and dry," Hawk said.
The concern would be the fluctuation of water levels in the pool and a loss of water quantity that industrial and municipal water intakes rely on, he said.
If the dam would fail and collapse into the river, Hawk said it would close the section of the river between Locks and Dams No. 5 in Natrona and 7 in Kittanning to river traffic.
That could create problems for industries that depend on the river for supplies such as power plants that receive coal by barge.
"That lock and dam, at this point in the season, would be used by commercial traffic by appointment only,"
Hawk said. "We will continue to do that. Unless the dam fails, this (repair) won’t close our lock operations."
A hydropower power plant at the dam, owned by Sithe Energy of Ford City, a division of Dynergy, Houston, Texas, would be severely damaged and have to cease operations, according to Hawk.
Sithe manager Robert Hanna said a lock collapse would put the company "...out of business."
"We are cooperating with the Corps in every way possible," Hanna said. "We control the pond level and can lower it to assist the engineers in inspections and repairs. Normally at this time of year you pray for rain, however, right now we're praying for it to hold off a bit."
Sithe sells hydro-produced electric power directly to Allegheny Power. Hanna said if the company's hydro-generating plant is shut down, Allegheny Power would have to increase the output of its coal generating plants to meet customer demands.
Erosion problem
According to Hawk and Ferris, the base of the dam wall downstream is being undermined.
It affects about 200 feet of the roughly 1,000-foot dam on the side where a hydroelectric plant is located.
At its worst, it extends two-thirds of the way into the dam and about 15 feet below the apron, Hawk said.
In the recent inspection, a remote-controlled submersible vehicle was used first and then a dive team was sent in to film the damage, which was then examined by engineers, Hawk said.
Ferris said Dam No. 6 rests on wooden pilings.
The fix
Although the contractors will come up with their own proposals, Hawk expects the fix to be similar to a repair made to Lock and Dam No. 3 along the Monongahela River.
That involved pounding in metal sheet piling along the dam wall down to the apron, then drilling into the dam and injecting a concrete grout to fill in any voids.
"It’s like a flowable concrete and that provides some stability against the sheet piling," Hawk said.
A rock rip-rap would then be placed below the dam to provide additional protection downstream.
"We have to figure out what is causing this (erosion)," Hawk said. "We work very hard to find that erosion and curb it when we find it."
The situation brought an immediate response from James McCarville, executive director of the Port of Pittsburgh, who underscored the need for more financial help from the federal government to maintain the locks and dams.
"The erosion at Allegheny Lock and Dam No. 6, and the danger it poses, is symptomatic of a long-term problem affecting almost all of our locks and dams," McCarville said.
"While intelligent and annual maintenance would be the logical, proactive and efficient solution to maintain our aging navigation infrastructure, the historic lack of such funding is not only risky to commerce, but it is a much more expensive way of maintaining our waterways — clearly pennywise and pound foolish."
Ferris said the Allegheny River locks and dams have lasted twice as long as they were expected to when built and he credits the Army Corps for keeping the locks operational.
Ferris looks to Congress to provide much more money in order to prevent some future disaster somewhere along the nation’s rivers.
Lock 6 is 80 years old with construction starting in 1927 and opening for river traffic in 1928.
According to Corps of Engineers records, Lock 6 had 111 commercial vessels, 98 empty barges, 61 loaded barges, and 916 recreational vessels pass through in 2007.
Tom Yerace can be reached at tyerace@tribweb.com. Tom Mitchell of the Leader times contributed to reporting this story.<>