Up the River with a Pump
Up the River with a PumpLuther Stem of Luther Stem Concrete Pumping in Fort Smith, Ark., never thought he would be taking a boat to work in the morning. But that's what happened when he started a special bridge project for the Jensen Construction Company. On a regular basis, his 28Z-Meter Putzmeister boom pump would be loaded on a barge and taken out on the Arkansas River to pump casings in a most challenging manner.
Difficult bridge jobs with limited access and challenging terrain was the norm for the pumping company, as Luther had worked with this same contractor on the Interstate 49 project between Fayetteville and Fort Smith. That job covered 40 miles with more than 20 bridges and overpasses, some as long as a half mile and up to 215 feet tall.
As a result, Keith Ulmer, area manager for Jensen, called upon Luther's services once more. This time the job required spanning the Arkansas River just below the Kerr Dam, located approximately nine miles from Sallisaw, Okla.
This would be the third bridge built at this site over the past 65 years. The first bridge, a small narrow span across the river, had to be torn down when the McClellan Kerr River project began in the late 60s.
Existing bridge to be torn down
The second and present two-lane bridge was built to accommodate barge traffic on the river, but it will be torn down when the third new and much larger 1,600-foot-long by 84-foot-wide bridge is completed within the next 8 to 12 months.
The pier work near the water's edge started in May 2001, consisting of 12 piers 9 feet in diameter and ranging from 40 to 70 feet deep. The first pier was pumped on May 24, 2001, at the bridge's south end, approximately 200 feet from the water. The remaining 12 piers out in the water were bigger at 12 feet in diameter and about 100 feet deep. The first of these 12 deep-river piers was pumped on July 9.
Getting concrete to the remote location on the water provided the greatest challenge. Because of river traffic and the river's swift current just below the hydroelectric dam, running line over barges was ruled out. Dumping via crane and bucket directly into the casings was not the answer, as they wanted to prevent voids in the concrete.
The only logical alternative was to load the company's newest 28Z-Meter Putzmeister boom pump onto a barge, head down river from the dam to the bridge site and pump the casings. The 28-Meter Z-fold was chosen because of its compact size, which would allow easier transporting on the barge. Once there, the barge (with pump atop it) was set up alongside the work platform surrounding the pier.
Sponge inserted in pipe
Jensen workers vertically hooked together three 30-foot-long sections of 5-inch pipe with heavy-duty welds on the ends. A sponge was put in the end of the pipe before it was lowered to the bottom of the riverbed to keep it from filling with water. The pump was hooked up with a 12-foot-long 5-inch hose and inserted into the pipe. When ready to start the pour, the total 90-foot section was raised about 18 inches off the bottom of the river via a crane on an adjoining barge, and the pumping began.
The concrete was a 4000-psi Class A State mix with 3/4-inch aggregate, ranging from a 7-inch to 8-inch slump. Mid Continent Concrete Company supplied all the concrete from their Sallisaw, Okla., branch nine miles away.
Their mixer trucks backed down a ramp to the river's edge where they unloaded into three lay-down buckets, each holding about 4 cubic yards. The buckets were lifted onto one of two barges and floated out to the work platform. At that point, a second crane on a barge would pick up the buckets one at a time and dump into a large 4-cubic-yard bin that Jensen had constructed to snugly fit around the hopper of the Putzmeister 28-Meter Z-fold pump.
Even though the concrete was handled a great deal by going from one location to the next, an impressive rate of 50 to 60 yards an hour was still attained. As the pumping continued, the pipe was raised a little at a time. The coordination between the crane and pump was crucial, making sure not to kink or pull too hard on the hose and to let the crane do all the lifting.
Re-hooking took only 10 minutes
Gradually, the sections were raised out of the water; and the crane and pump operators simultaneously swung them down onto two steel girders positioned on a barge. Then, they would unhook the hose from the pipe, go back to the pipes that were still in the water, re-hook and start pumping again. Although this particular part of the process sounds time-consuming, it only took about 10 minutes. Usually the equipment was ready to pump before one barge could pull out and another back in.
As there could be absolutely no interruptions in pumping until the concrete started pushing out of the water at the top of the casings, Ron Barnes, Jensen's general superintendent questioned the reliability of the pump. Luther said, "I told him I wasn't worried one bit. I wouldn't take on a job like this if I didn't have complete confidence in my pumps or operators."
Luther also noted that he enjoys working with companies like Jensen. "They know what they are doing and will work with you to get the job done right."
Although problems can occur with any piece of equipment at any time, every pier was pumped without a hitch. Plus, it was done in one of the hottest settings — a red barge in the middle of the Arkansas River during the scorching summer months.
Noise created a challenge
Not only was it extremely hot on the water, but it was also exceptionally noisy. The noise of the river traffic, barges and working cranes added to the loud sound factor.
Luther said, "Because of the noise, I would often go over to the pump's hopper and look inside just to make sure it was pumping. There were times the pipe's end would be 10, 15 or even 20 feet deep into the concrete and the boom was hardly moving."
The twelve different pours out in the 30-foot river consumed about 425 yards of concrete each, and they usually lasted about eight hours.
Since the completion of all the pier work, Jensen has been setting the bridge beams in preparation of the deck work that should start sometime early this summer. Because of the width of the bridge and height over the water, some of the pours will need two pumps - one on each side of the center barrier. Once extended over the bridge deck, each pump will be stretched out to its maximum reach and 300 feet of 5-inch pipe added on. A mini placer will be used to further assist.
To date, Luther Stem Concrete Pumping has pumped more than 7,000 yards of concrete with 3,500 to 4,000 yards still remaining. The $20 million project should be completed in late 2002 or early 2003.
Luther summed it up best by saying, "I like to pump concrete because every day is different. You go somewhere different, do something different and have the opportunity to work with different people. This bridge job and going to work by boat has certainly been yet another positive experience in pumping concrete."