A Dam Fast Underwater Concrete Pour
A Dam Fast Underwater Concrete PourStrategic setup of boom pumps and an expert crew rapidly accomplish two underwater concrete pours during urgent construction of water control weir
STURTEVANT, WI (February 16, 2009) – To beat the peak of Florida’s 2008 hurricane season, the emergency construction of the S-65E Tailwater Weir project tested the speed, ingenuity and around-the-clock performance of contractors and Putzmeister truck-mounted concrete boom pumps to build a specially-designed water control weir or lowhead dam in the Kissimmee River.
Construction of the $18.6 million weir, the largest single structure ever built by the South Florida Water Management District (SFWMD), required 4.6 million pounds (2,086,525kg) of 70-foot-long (21.34m) steel sheets and 110 million pounds (50,000,000kg) of riprap and bedding stone. It also required a special strategy to quickly place 5,450 total cubic yards (4,167m³) of concrete underwater, challenging the equipment and construction crews to perform under extraordinary conditions.
“Typically, this type of project would take at least a year to build,” says SFWMD lead project manager Kathleen Collins, P.E. “However the new weir was functional on August 2, just five months after its March 2008 construction start date and even 14 days ahead of its accelerated construction schedule. Everyone involved in the project did an amazing job.”
A Weir Necessity
Though a two-year water shortage and rainfall deficit steadily dropped Lake Okeechobee’s water level to an all-time record low of 8.82 feet (2.69m) on July 2, 2007, the SFWMD had concerns about strengthening its flood protection system in Florida’s unpredictable climate.
Due to the drought conditions, static stability failure at the S-65E water control structure was likely to occur. Therefore, the SFWMD deemed construction of the S-65E Tailwater Weir necessary and, thus, began the largest and most complicated of four emergency improvement projects undertaken in 2008.
The new weir is designed to reduce head differential and relieve water pressure at that structure, which would lessen the exposure to flotation, sliding and scour. The weir acts as a small overflow-type dam for managing the level of the river downstream of S-65E, which is the last gated spillway on the Kissimmee River before discharging into Lake Okeechobee.
On the heels of Tropical Storm Fay, just weeks after the weir’s completion, SFWMD transitioned almost overnight from managing a water shortage to lowering canals for flood protection.
“Without the weir, there was a real possibility that S-65E would not have withstood the impact from the historic deluge brought by Tropical Storm Fay,” says Collins. “Serious flooding might have been the result of failure.”
Ironically, building a weir to reduce water pressure literally meant adding pressure on contractors to meet a compressed completion date before peak hurricane season arrived. It also required crews to tackle a complex tremie pour.
The Florida-based companies responsible for the concrete placing feat included general contractor American Bridge Company (AB) of Tampa, known for their strong marine construction capabilities; concrete pumping contractor Brothers Concrete Pumping Service, Inc. (Brothers) of Fort Lauderdale, a locally owned and operated business with over 30 years experience pumping concrete; and ready mix supplier Maschmeyer Concrete Company of Florida, Inc. (Maschmeyer) of Lake Park, equipped with over 60 ready mix trucks, four batch plants and a portable job site plant.
The distinctive weir, about a mile downstream of S-65E, was built with eight 58-foot (17.68m) diameter filled sheet pile cells, four on each side of the canal, forming an L shape. Circular cells were utilized for more uniform water pressure and improved stability atop clay soil. Between the cells, the 200-foot-wide (60.96m) weir required two lines of sheet pile separated by an eight-foot (2.44m) thick concrete scour mat, 90 feet (27.43m) long. The large, deep concrete base would ensure that water pressure wouldn’t uplift the structure as the river was forced through the weir.
A Strategic Plan
The unusual placement of concrete underwater demanded a fast, smooth and continuous tremie pour. Taking the lead roles, Steve Degen, Brothers sales representative, and Allen Dronko, AB project manager, developed a highly strategic plan to meet the job’s special demands.
The complex undertaking was divided into two pours with 2,750 cubic yards (2,100m³) of concrete placed for the first pour in June 2008, and 2,700 cubic yards (2,065m³) for the second one a month later. Skillfully executed under the direction of AB superintendent Marc Wooten, each pour required a fast concrete output for a targeted completion within 20 hours. To meet this specification, the plan employed a tactical layout of four Putzmeister truck-mounted concrete boom pumps selected for their long reaching booms, smooth concrete flow and high volume pump cells.
Roller Coaster Journey
“The schematics of equipment setup were similar for both pours, except for using different boom pump models based on the reach needed from land,” says Degen. “The two pours were finished far earlier than the 20-hour goal, with the second one the faster of the two. It averaged 170 cubic yards an hour (130m³/hr) output for completion in only 16 hours.”
Equipment setup resembled a roller coaster ride, as the concrete journeyed up and down concrete delivery line en route to its final destination. The second pour, for example, featured a 52Z-Meter truck-mounted boom pump positioned on solid ground, where it extended its long 157-foot 6-inch (48.01m) horizontal boom to reach a barge. At this point, the unit’s 10-foot-long (3.05m) end hose was connected to 90 feet (27.43m) of slick line, which was anchored on the barge using U-bolts and redheads. The slick line bypassed the second boom pump’s hopper also on the same barge and connected to deck pipe at the back end of a 58-Meter boom pump.
The concrete continued its journey 174 feet 3 inches (52.10m) horizontally through the 58-Meter boom that reached over water. It then went through the boom pump’s end hose and tremie pipe. The tremie pipe’s lower end was kept immersed in fresh concrete so the rising concrete from the bottom displaced the water without washing out the cement content.
About 120 feet (36.58m) away, a similar equipment arrangement incorporated a 42X-Meter boom pump set up on land, with its boom fully extended 124 feet 8 inches (38m) horizontally to access a second barge. Its end hose was connected to 90 feet (27.43m) of slick line, which traveled to deck pipe at the backend of a 46X-Meter boom pump, again bypassing the hopper. The concrete continued 136 feet 2 inches (41.50m) through the 46X-Meter’s outstretched horizontal boom, its end hose and tremie pipe, which also placed concrete into the submerged structure.
Although a detailed engineering layout indicated the precise placement of equipment, barges and slick line, the location of the alligator audience was missing. The mere presence of these reptiles nearby added to the intensity on the job site, as the crew kept one eye on the surrounding water while busy working to meet an aggressive schedule.
Smooth yet Powerful
The two truck-mounted boom pumps on barges were specifically used as placing booms, as the two boom pumps on land were the real workhorses. Their high pressure .16H pump cells pumped concrete the entire distance, traveling up and down an extensive amount of delivery line from the unit’s hopper on land to its final point of placement.
“This job was a testimonial for the power of the boom pumps on land to effortlessly push the concrete at long distances over 450 feet (137m),” says Degen, “and the units still achieved high volumes that were recorded up to 230 cubic yards an hour (176m³/hr) during peak performance.”
Smooth concrete flow was also critical to the project’s success. “To maintain the integrity of the concrete during an underwater tremie pour, the boom must remain steady in order to keep the lower end of the tremie pipe embedded in concrete,” says Jim Henegar, co-owner of Miami, Florida-based Thomas Machinery, Inc., an authorized Putzmeister distributor. “A smoother flow without boom bounce was achieved with the pump’s exclusive free flow hydraulics.”
“The closed loop design of the free flow system provides infinitely variable output control for smoother pumping,” adds Henegar. “Additionally, it generates less heat and requires less horsepower, which results in a cooler running hydraulic oil system and less fuel consumption.”
“The pumps’ pressure ran at about 2,900 psi (200 bar), and the temperature never exceeded 140 degrees Fahrenheit (60 degrees Celsius),” adds Degen. “The units were pumping smoothly and not being taxed whatsoever.”
“We finished both pours in record time, which was up to 20 percent faster than required in the specification,” says Paul Merson co-owner at Brothers. “This performance by our equipment and boom pump operators especially impressed one of American Bridge’s senior managers who was scheduled to see the last part of the second pour, but missed it because we finished four hours earlier than planned.”
A Cool Mix
Both pours occurred over a weekend, starting at five o’clock in the evening and finishing up the following morning. As concrete temperature was a major concern, a special 3,000-psi mix was specified that incorporated a 70 percent blast furnace slag and super-plasticizers.
“Maschmeyer consistently produced an excellent mix that pumped like ice cream,“ says Degen. “Plus they did an outstanding job of continuously supplying the concrete to keep up the volume.“
For the long periods of non-stop pumping during the two different pours, Brothers stationed a mechanic and a backup boom pump on site. Although the mechanic did oversee pumping operations, he was not called upon to handle any equipment malfunctions. The same holds true for the spare boom pump, which was never needed due to the pumping equipment’s reliability.
“Typically on a pour like this, we expect at least a hydraulic hose to fail on a boom pump; but we didn’t have any service issues, not even a blown hose,” says Dronko. “The equipment worked perfectly, and Brothers did an exceptional job from setup to teardown.”
“Not one single mechanical breakdown occurred during the 17.5 hours of continuous pumping on the first pour, or during the 16 non-stop hours on the second one,” says Steve Merson, co-owner at Brothers. “That type of reliable performance shows the backbone of our Putzmeister equipment.“
“For dependable pumping, we also strongly emphasize equipment maintenance,” notes Steve Merson, who additionally credits the concrete pumping company’s success to meticulous service and maintenance since 1978 when the two Merson brothers established operations. Today, the family-owned company includes a main location in Fort Lauderdale and a satellite branch in Stuart, Florida, which totals over 35 experienced employees and a sizeable fleet of 15 truck-mounted boom pumps, five separate placing booms and 13 trailer-mounted pumps.
As a result of the two successful concrete pours, the project met its completion date.
“I’ve been involved in numerous projects over my 28 years in concrete pumping, but never one of this duration and intensity,” says Degen. “I’m really proud that both pours went so smoothly and that we did our part in reliably and efficiently pumping the concrete to keep this job on schedule.”
“Brothers came through for us when we needed it,” notes Jack Chenneville, AB senior project manager who acknowledged the value of its vendors to accomplish the difficult project within a short time frame.
“Teamwork made a huge difference on this emergency project,” concludes Dronko who credits the entire construction team for their 24/7 dedication in finishing the weir 14 days ahead of schedule. Unbeknownst at the time, this major accomplishment would ultimately make a huge difference in avoiding more serious consequences when Tropical Storm Fay hit the region so soon after the weir’s completion. In addition, the weir’s flood control benefits were again realized when hurricanes Gustav, Hanna and Ike missed South Florida but still unleashed substantial rains.
The new weir, having already proven effective, can pass up to 30,000 cubic feet of water per second (850m³/sec) or enough water to fill 1,000 swimming pools in a minute. This allows proper design discharge, protects the structural integrity of S-65E and facilitates operation of the flood control system under severe conditions.