In the Wet
In the WetPutzmeister concrete placing system places tremmie concrete for the Olmsted Locks and Dam project
STURTEVANT, WI (November 1, 2010) – As part of one of the last phases of the Olmsted Locks and Dam Project, a Putzmeister concrete placing system is placing up to 140,000 cubic yards (107,308m) of tremmie concrete via the “In-the-Wet” method, a first in the United States, for the new Locks and Dams No. 52 and 53.
Located on the Ohio River beginning in Pittsburgh, Pennsylvania and flowing west 981 miles (1,579km) to the Mississippi River at Cairo, Illinois, are 19 modern locks and dams that provide a nine-foot (2.74m) depth year-round channel for navigation that will allow the traffic on the river to lower from an elevation of 710 feet (216m) at Pittsburgh to an elevation of 250 feet (76m) above sea level at Cairo, Illinois, dropping a total of 460 feet (140m). The continued increase of water-borne commerce on the Ohio River has required periodic improvements in the waterways transportation infrastructure.
Two of the current locks and dams, No. 52 and 53, originally built in 1929 and located on the Ohio River between Paducah, Kentucky and Cairo, Illinois, cannot meet the current and future traffic demands without significant delays because of their age and dated design.
As a result, the U.S. Army Corps of Engineers (the Corps) and the navigation industry are replacing Locks and Dams No. 52 and 53, one of the largest civil works projects undertaken by the Corps.
Construction of the 20th and final lock of the Olmsted Locks and Dam Project at river mile 964.4 was authorized by the U.S. Congress on November 17, 1988, by passage of the Water Resources Development Act of 1988 (Public Law 100-676).
Construction for the project began in November 1992.
Several phases make up the Olmsted Locks and Dam project:
1. Access Road/ Resident Engineers Office (Completed June 1994)
2. Lock Cofferdam (Completed December 1995)
3. Lock Construction (Completed March 2002)
4. Bulkheads (Completed July 2005)
5. Lock Approach Walls (Completed April 2004)
6. Dam Construction (In progress)
7. Demolition of Locks and Dams 52 and 53 (upon completion of the dam construction)
The joint venture Washington Group Alberici (WGA) was awarded the $564 million contract from the Corps for construction of one of the last phases of the project, which includes constructing a 2,700-foot-long (823m) concrete dam across the river. The dam will comprise five, 110-foot (33.5m) tainter gates and a navigable pass section with boat-operated wicket gates along with a fixed weir tying the dam into the Kentucky bank.
Construction began in spring 2004 and the estimated completion date is December 2015.
The dam is being constructed using the "in-the-wet" method, a first for the Corps on a dam of this size. The “in-the-wet” method is where the construction of a dam is done under water. Normally, the water is drained out of the dam and the construction work is done “in-the-dry.” The “in-the-wet” method was used because WGA wanted to gain experience in using the method as well as knowledge of equipment technology used using this method.
“There is nothing standard about this job,” says James Whitworth, marine engineer with WGA. “The ‘in-the-wet’ method required us to think outside of the box to figure out how we would construct the dam underwater. We had to determine which equipment would be the most efficient in this unique job environment.”
As part of the dam construction, precast shells are being constructed on land adjacent to the dam location and are being floated into position and set underwater on a prepared bed of select fill, piles and continuity rebar grids. Once the shells are in place, tremmie concrete is tremmied under the precast shells to form a continuous bond between the piles, rebar, and surface shell, and provide more strength and fuller foundation overall for the dam.
WGA consulted with Putzmeister’s Special Applications Business (SAB) to help figure out what equipment would be best suited to deliver the tremmie concrete.
SAB is a partnership between Putzmeister America, Allentown Shotcrete Technology, Inc., Esser Pipe Technology and Maxon Industries, Incorporated (Maxon).
“Through the complete systems approach,” explains Whitworth, “they offer all products to all projects for various industries, including dams. After discussing with SAB the specific needs of the project and the environmental circumstances, we determined that they could provide us a complete concrete delivery system for the dam construction. They don’t just sell one component of a system, they manufacture and provide every component of the system, and that’s huge because it means less time I have to search for another company that has the other system components needed.”
The equipment that SAB proposed and is being used to deliver the tremmie concrete includes:
• Two freestanding MX 42/46Z-Meter placing booms mounted on two freestanding pin towers
• One 31-Meter placing boom
• Two BSA 2112 skid-mounted concrete trailer pumps
• One 40-Meter truck-mounted concrete boom pump
• Four Maxon Maxcrete IV 18-cubic yard (13.7m3) remix hoppers
• Two DVH 5/2 diversion valves
The equipment arrived on site in early spring 2010.
The Mix, Equipment and Process
The tremmie concrete mix the system is delivering is a self-leveling mix to ensure that it fills up every square inch under the shell for ultimate strength.
“The mix’s strength is 5,000 psi (34 MPa) at 90 days and has a 10-inch (254mm) slump,” comments Whitworth. “It does not need any vibrating.”
Placing the concrete for each of the 28 shells is a non-stop 36-hour, step-by-step process.
First, the 40Z-Meter truck-mounted concrete pump, located on the river side of the project, delivers the concrete through 300 feet (91m) of slickline across the lock chambers.
“The 40Z not only helps to deliver the concrete quickly through the slickline with up to 210 cubic yards per hour (160m3/hr) output, but it also allows for smooth and controllable pumping with its free flow hydraulic system,” notes Whitworth. “And that’s what we need for these long pours.”
In addition, the boom pump works with pressures up to 1,233 psi (85 bar).
Then, at the end of the slickline is the 31-Meter placing boom that places the concrete into the four stationary mixer drums on each of the two delivery barges.
“The 31-Meter placing boom is perfect for customized applications like ours, providing us the utmost versatility in the concrete placement process,” comments Whitworth.
Next, the delivery barges go to the placing barge where the stationary mixer drums dump the concrete into the Maxcrete remix hoppers.
Two delivery barges are constantly rotating between the 31-Meter boom and the placing barge to provide the most efficient placement of concrete during the non-stop pours.
“The remix hoppers offer fast loading, fast discharge and complete remix capabilities,” says Whitworth. “And those characteristics are crucial to the project given our non-stop pour process; it’s almost as if this style of remixer was made specifically for this project.”
The remix hoppers then place the concrete into the hoppers of the BSA trailer pumps.
“The two BSA 2112 trailer pumps performance has been outstanding,” comments Whitworth. “We’ve been averaging 100 cubic yards per hour (76m3) from each pump but they are capable of pumping up to 142 cubic yards per hour (109m3). The rate of output from these trailer pumps has been vital in ensuring we stay on track with how much concrete needs to be placed.”
Two DVH 5/2 diversion valves are hooked up between the BSA 2112s and the MX 42/46Z placing booms.
“The diversion valves have been an added support of muscle within this system,” explains Whitworth. “They provide the flexibility to use either trailer pump with either placing boom, and provide cleanout routes. In addition, the valves can easily handle high pressures up to 1,885 psi (130 bar) without leaking.”
After the trailer pumps and diversion valves, the concrete travels up to the two MX 42/46Z placing booms. Here is where the concrete is placed into the tremie pipes that travel underwater to its final resting place underneath the precast concrete shells.
The two Z-Fold, five-section MX 42/46Z placing booms are the largest placing booms in the industry that do not require a counterweight.
“Not needing a counterweight on these placing booms saves us time and reduces labor costs,” says Whitworth. “Anywhere we can save time and money is a huge benefit to us.”
Both placing booms’ reach has proven to be invaluable on site as well.
“Their monstrous 138-foot one-inch (42.09m) horizontal reach places concrete exactly where we need to into the tremmie pipes,” adds Whitworth. “With these pours being nonstop, we don’t have time for a system that doesn’t place the concrete precisely where it needs to be.
“To-date, the concrete placing system has delivered 2,000 cubic yards (1,529m3) of concrete for one precast shell,” explains Whitworth. “The system will deliver up to 5,000 cubic yards (3,823m3) of concrete for each of the remaining pours.”
The concrete placing system is estimated to be on site through 2015.