Pittsburgh Post-Gazette
29 October 2008
By Don Hopey,
Severe erosion under Allegheny River Lock and Dam No. 6 above Freeport, Armstrong County, threatens to undermine the stability of the dam and will necessitate emergency repairs
A recent inspection of the 80-year-old Army Corp of Engineers navigation dam by divers discovered the erosion underneat the downriver "toe" of the dam, which makes it vulnerable to failure if hit by barges, ice flow or high water
Because the dam, 32 miles upriver from Pittsburgh's Point, is a navigation structure and not a flood control dam with a large reservoir behind it, the corps said yesterday there is no immediate threat to public safety or flooding concerns.
"There's not any danger to life," said Jeff Hawk, a corps spokesman. "Basically a dam failure would drain Pool 6 and cause loss of navigation capacity for commercial an recreational river users and short-term water degradation."
Most of the Lock and Dam No. 6 use is by noncommercial, recreational boaters because it is upriver from most industry and power plants. According to corps statistics, 916 of the 1,037 vessels that locked through the dam between river pools 5 and 6 last year were recreatioonal boats.
But failure of the dam would also impact public water supplies and industry intakes along that section of the river, damage or destroy a hydropower operation on the dam and drain the Cogleys Island wetlands, one of the region's largest. It could also damage beds of federally listed freshwater mussels
The erosion undercuts approximately 200 feet of the 1,140-foot-long lock and dam structure. At its worst, it extends approximately two-thirds of the way under the dam, Mr Hawk said.
He said a pre-bid meeting was held at the dam yesterday for six contractors. They will submit bids for the work, which should begin in six to eight weeks and be finished before the end of the year.
The repairs will consist of sinking metal pilings and sheets into the water below the dam and packing rock behind it to stabilize the structure.
"It's a fairly simple fix, nothing extravagant," Mr. Hawk said. "It will provide stability to the dam and allow it to continue to operate."
Similar emergency repairs to the eroded "scour" below the Emsworth Lock and Dam on the Ohio River, 6.2 miles below Pittsburgh, were made in 2005, and the corps plans to spend about $20 million for more foundation support work at that structure in 2009 and 2010.
The Allegheny No. 6 Lock and Dam complex is one of eight corps' navigational dams on the Allegheny River. There are another 15 navigational dams on the Monongahela and upper Ohio rivers, almost all of them old and in need of critical repairs.
Pittsburgh is the second-busiest inland port in the nation, shipping and receiving more than 40 million tons of cargo a year, about 70 percent of it coal for power plants, steel and coke mills.
In a State of the Infrastructure report in July, the corps reported that the Pittsburgh District system of locks and dams is the nation's "oldest, largest and most fatigued navigation system in its inland waterways inventory."
"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," said James R. McCarville, executive director of the Port of Pittsburgh Commission.
"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 proves to be a much more expensive way of maintaining our waterways, clearly penny wise and pound foolish."
Don Hopey can be reached at dhopey@post-gazette.com or 412-263-1983.
First published on October 29, 2008 at 12:00 am