Putzmeister Pumps Help Booming Arkansas Region Keep Infrastructure On Track with Economic Growth April 2004
STURTEVANT, Wis. (March 29, 2004) – With a host of high-profile companies based in northwest Arkansas, the area including the communities of Bentonville, Rogers, Springdale and Fayetteville now boasts the nation’s sixth fastest growing economy.
Retail giant Wal-Mart, meat producer Tyson Foods, the huge trucking company J.B. Hunt and the University of Arkansas, all located along a 30-mile section of Interstate 49, are key components in the region’s powerful economic engine.
But because of the continued influx of businesses and people, pressure is increasing on existing infrastructure such as wastewater treatment plants.
To keep pace, the city of Springdale is undertaking a major expansion and upgrade of its wastewater treatment facilities. BRB Contractors Inc., Topeka, Kan., was awarded a $29 million contract for the project that began during the summer of 2003.
The work involves constructing a number of new amenities including buildings to house grit and scum removal processes, polishing filter equipment, sludge processing machinery, an effluent pump station, a booster pump station and process trains, which alone will consume 11,000 yards of concrete. Overall, the project will demand more than 20,000 yards of concrete.
The process trains, the largest phase of the project, is basically a huge concrete basin some 461 feet in length and 240 feet wide. Wastewater enters one end and flows through an aerated raceway. The structure encompasses a 19-foot-high wall that is more than 2,000 feet in length and ranges in width from 12-20 inches. Waste breaks down into progressively smaller particles as it travels through various sections of the basin and ultimately enters the final clarifiers.
Having worked together previously on three other water treatment projects, BRB Contractors Superintendent Steve Homewood again called on Luther Stem Concrete Pumping, Fort Smith, Ark., to handle all concrete placement.
“I started working with BRB on a job in Oklahoma about four years ago where we pumped 10,000 yards of concrete at the city of Norman Wastewater Treatment Plant,” Luther Stem, owner of the concrete pumping company, said. “Since then, we have worked together at Stillwater, Okla., and we recently completed a project for the city of Fort Smith. We know the BRB employees and have a great working relationship with them.”
The first pour at the Springdale plant was made on July 23, 2003. “We started with our 43-Meter Putzmeister pump on the east end of the aeration basin,” Stem said. “Since the basin was approximately 20 feet in the ground, we needed as much reach as we could get for the pours. We made several floor-section pours across that end of the basin and started moving down the north side when a problem surfaced.”
Although numerous geological studies were conducted of the area and test holes had been drilled to pinpoint any areas of concern, a small section of the basin caved in when a dump truck was driven over it. The area was excavated and flowable fill was poured into the hole.
After another hole formed a short distance away, engineers decided to drill a series of holes, 6-inches wide and 40-feet deep and to fill them with a grout mixture to eliminate any other potential voids. Approximately 1,200 holes were drilled on an 8x8-foot grid stretching the entire length and width of the structure.
At first, the company drilling the holes also was pumping the grout, using a small line pump and 2-inch-diameter hose. When water was discovered in some of the holes, engineers called for pumping of the grout to start at the bottom of the holes so the water would be forced out ahead of the grout.
Homewood asked Stem if he could devise an efficient method of getting grout down the small holes. “At first, I hooked a 2-inch hose onto my 28-Meter pump using pipe reducers. That worked fairly well until a rock or something wedged the hose into the hole and we couldn’t pull it out with a backhoe,” Stem said.
“It looked rather funny, like a bird pulling a worm out of a hole. Except every time the backhoe operator would let off the controls, the hose would go back down into the hole.”
Not wanting to lose another hose, Stem came up with an alternative plan. “I took four sections of lightweight conduit and coupled them together and welded a 2-inch weld-on on one end of the pipe. It didn’t weigh anything, but we had to be careful lifting it into the air for fear of it breaking at the threaded couplings. We had it safety strapped at every section and it worked fairly well. I did most of the pumping on the holes myself with my oldest pump, my 28-Meter. It has a smaller pump cell and is really smooth when you need to pump slowly.
“I would lower the pipe all the way into the holes until the reducer was right at the top of the ground. We would start pumping and slowly raise the pipe filling the voids. Most of the voids didn’t take much grout, maybe four or five strokes of the pump. On the other hand, we had one hole that took over 130 yards of grout.
“Even though we were using a very liquid sand and cement mixture, I fashioned a screen to go over the hopper grates to catch anything big, like oversized rocks or debris that might clog up the reducers. All told, over 1,700 yards of grout was used to fill all the holes.”
Once the void problem was eliminated, concrete pouring began in earnest and at a rapid pace. “We have been making two to sometimes three pours a week,” Stem said. “They usually have three or four floor sections to do in the morning, followed by a wall section or two in the afternoon. We are looking at nearly a year just to finish the process trains basin and another year to finish the entire job.”
Stem said he has used every Putzmeister pump in his fleet. “Most of the pours have been made with my 28Z-Meter and 36-Meter pumps,” he said. “Occasionally we need the 43-Meter to reach over one section of wall that has already been poured and make a floor pour on the other side. It’s a fairly large hole in the ground. We’ve been making pours there since this summer and looking at it now, it looks like we still have a long way to go.”
Most of the pours have been in the range of 100-150 yards, but four pours on the grit and scum removal-building floor each exceeded 300 yards. Arkhola Ready Mix, Springdale, is providing a 4,000-psi mix that has been pumped without a problem.
“Jobs like the wastewater treatment facilities are our bread and butter,” Stem said. “When you know that you are going to be pumping consistently one or two times a week for 18 months, you count your blessings. That’s why we do our best to take care of our best customers like BRB. We know what they expect from our pumps and our operators and we do our best to deliver.”
Luther Stem Concrete Pumping was founded in the 1940s by Stem’s grandfather, Luther N. Stem Sr., who started the business as a dump truck service. Stem’s father, Luther N. Stem Jr., took control in 1951. In 1962, he built his first swimming pool in his own backyard. Soon afterward, people began asking him to build them a swimming pool.
That is how Luther Stem Pools & Spas developed. As the oldest swimming pool company in Arkansas, the business specializes in building custom residential concrete swimming pools with designs such as rock waterfalls, free-form layouts and custom water features.
In the 1990s, the present owner, Luther Stem III, expanded the business to include a concrete pumping division with a fleet of Putzmeister equipment. Now he takes on a variety of challenging pumping projects, using his problem-solving capabilities to handle jobs like the wastewater treatment plant.
JOB SPECS: Owner: City of Springdale, Ark. General Contractor: BRB Contractors Inc., Topeka, Kan. Concrete Supplier: Arkhola Ready-Mix, Springdale, Ark. Pumping Contractor: Luther Stem Concrete Pumping, Fort Smith, Ark. Equipment: Putzmeister 28, 28Z, 36 and 43-Meter concrete boom pumps