The words "faster, better, cheaper" are sweet music to the ears of any serious steward of the taxpayers’ money, and this summer the Hurley delivered.
"Historical dredging costs have averaged $16.75 per cubic yard, and the Hurley cost $6.41 per cubic yard," explained Olmsted resident engineer Brad Bradley. "The cost savings on the material it removed from the dam construction footprint is well over a million dollars and that doesn’t count the savings from improving the schedule."
It was the first time in the history of the project a dredge was used to clear the area on the river’s bottom where the dam shells would be placed. The Louisville District regularly contracts for cutterhead dredges to keep the navigation channel open on the lower Ohio River. The U.S. Army Corps of Engineers Dredge Hurley was chosen for it special features.
The 353-foot-long, 108-foot-wide dustpan dredge vessel is out of Memphis, Tenn. Its two 1,500-horsepower motors drive pumps that can remove as much as 5,000 cubic yards of sand and sediment from the river bottom each hour using a vacuum-cleaner type head and deposit it safely outside the navigation channel via a long floating pipeline. It can dredge as deep as 75 feet if conditions require, which they did.
Frank Segree, the master of the Hurley, headed up the 47-member crew who worked 12-hour-shifts around the clock moving the dredged material through 1,150 feet of pipe to be surface-discharged downstream. While the diesels hummed below decks, head cooks like Helen Howard were busy in the galley ensuring hearty, balanced meals sustained the force. Marine mechanic Cletus Russell from Mumford, Tenn., endorsed Howard’s culinary skill with a satisfied smile. "These meals are fantastic," he said.
Though it was the first time Segree had worked the Ohio River, the Vicksburg, Miss., native confirmed in his double bass voice it was pretty much business as usual: "Same kind of work, just a different place."
Barry Vessels was a key player in getting the Hurley and then the permits. As the Louisville District’s navigation and dredging team leader he’s also a member of the USACE Mississippi Valley Division’s regional shallow draft dredging team.
"The states require water quality permits for most river work, including dredging and open-water disposal," Vessels said. "The Kentucky Division of Water (KDW) handles the permits for most of the Ohio River which falls within the state boundaries."
The original Olmsted permit for clam-shell dredging required on-shore disposal, and Vessels had to establish open-water sites in 2012 for channel maintenance dredging due to the extremely low water. This spring he and Olmsted project manager Matt Lowe traveled to Frankfort for a face-to-face to allay KDW’s concerns about the potential environmental impact of more open-water disposal.
"The presentation quickly illuminated the time-event progression of large sand waves working past Olmsted which prevented the area from being a stable environment for mussels and fish," Vessels explained. Vessels was also able to address KDW’s apprehension about the fish spawning season April 15-June 15 by pointing out that the area for open-water spawning between Cairo and Smithland, Ill., covered more than 20,000 acres and the dredging and pile driving would impact less than 10 acres.
Bradley said the Hurley performed pretty much as expected. In addition to removing the sand wave, it dredged a large silt trench that he said is helping reduce sediment infill on the foundation footprint.
"The Hurley’s work around the pile heads on the tainter-gate footprint for Sill Shell 5 was experimental for us," Bradley said. "We did not get all the material removed from around the pile heads that we would have liked, but a large amount was removed and dive time on the footprint should be significantly reduced."
He estimated the Hurley has the potential to put the project schedule ahead by about six weeks on an annual basis when normal seasonal low-water conditions return.