Separate Placing Booms and Condo Boom Converge in Colorado
Southwest Concrete Pumping in Denver is experiencing a surge in separate placing boom work compared to past years. “We are a full service pump company and the market has really been pushing us to build with separate placing booms, “explains Bob Rosendale, co-owner of the 17 year old firm. As the city has sprawled up to the foothills of the Rockies and big city traffic woes have become the norm, a percentage of the population is seeking an urban retreat in downtown condominiums and lofts.
The timing couldn’t have been better for Southwest. “Just as the single family homes slowed down, this commercial condo work started to spring up, “ Rosendale explains. “And the contractors for these medium and high rise structures are savvy to placing methods.” Inevitably, limited access precludes truck-mounted boom pumps even if they could top out smaller structures. And trailer pumps must be accompanied by a placing boom. “Dragging hose is just not an option when the majority of these projects are post-tensioned cast-in-place structures with caissons, decks, columns and core walls,” Rosendale states.
In developing their separate placing boom skills, Southwest has adopted several different methods of mounting, lifting and placing. In addition to solving access problems, an early set-up gets the efficiencies of the separate placing boom involved from the start. Southwest utilizes detachable booms whenever possible. These units allow the boom to be easily separated from the truck for mounting on top of masts. This allows them to operate high utilization pumps that can place a foundation wall in the morning and detach the boom in the afternoon for deck pours on a high rise. The company owns Schwing truck pumps with detachable booms in 28, 32 and 39-meter sizes. “We made the decision to purchase detachables before we had these jobs and then the separate placing boom business started to take off, “Rosendale mentioned, “So the decision and the timing worked out well.”
Schwing high pressure boom pumps can be ordered with a detachable option to meet the needs of high rise placement but that works as an everyday pump with the boom attached. The KVM 39X models allow a powerpack with hydraulic reservoir to be purchased separately allowing the boom to be flown without this accessory to keep picking weight low.
This downtown Denver 8 story condo on Little Raven Street dictated that the boom be erected so early in the project that it was secured into the slab on grade. The 39-foot mast was set into a floor frame in the slab on grade and two feet of ground was dug out to leave room for the mast end. Another floor frame 14-feet up on the next deck secured the upper portion of the mast that supported a 28-meter placing boom.
“Access was so tight on this project, we had to position the pump three-hundred feet away from the standpipe,” explains Rosendale. Their experience on this project encouraged Southwest to develop a dedicated team for their placing boom projects to streamline assembly, lifting and pumping. “We look for the operators that have the ability and experience to perform repetitively without cutting corners,” explains Eric Ball, Southwest Field Manager. He mentioned that separate placing boom duty has become a prized profession at the company. “There’s a waiting list of operators.”
Southwest secured the pumping contract for a 27-story tower at 17th and Fillmore in the downtown core that is due to be completed in the Spring. This time the project required a 32-meter boom on a 39-foot mast secured in floor frames at the fifth level. Sales have been so brisk for a second tower that the mast and boom will be swung over to an adjacent site when the first tower is topped out.
“The contractor liked the performance of the placing boom so much that they want it installed sooner on the second tower,“ Rosendale noted, “The crew is placing over 80 yards per hour more than 270-feet up.” The Pinnacle is the tallest residential structure in Denver.
Southwest is using the truck pump at ground level to place the concrete. It utilizes a high-pressure2023-4 pump kit that applies 1007 psi to the concrete and offers 170 yards per hour output. The pump features high and low pressure settings. “We haven’t switched it to the high pressure setting and it is meeting all of our expectations, “Rosendale mentioned.
On this project, pour schedules have kept the boom on the site. When there is a break in the action, the truck pump can be driven to Southwest’s nearby shop for routine service in a more spacious and comfortable environment.
One Lincoln Park
Osborn Development Co., based in Denver, kicked off its 32-story One Lincoln Park project in March 2006 in downtown Denver. The groundbreaking was nearly a year ahead of schedule, due largely to brisk sales. Swinerton Builders, Arvada, CO is the general contractor on the project. In qualifying the placement method and brand of equipment to be used, Swinerton wanted to see other projects similar to One Lincoln Park. Southwest took the Swinerton superintendent to several projects – as far away as Miami – and won the contract over competitors.
‘After Swinerton concluded that we were their best choice to pump the project , we looked at the building site and realized this would be a unique challenge,” Rosendale recalls. One issue was that limited access on three sides of the project due to city streets and a light rail line precluded the use of boom pumps to reach all of the foundation work. Another issue was that two tower cranes were planned for the project, but the contractor announced later that the decision was made to go with only one. “Crane time became extremely valuable and they told us we could use the crane to set up the mast at the beginning and to take it down at the end…and that’s it.” This posed a challenge for the pumper. The elevations of the lower floors dictated that the mast be at ground level. “We called Schwing and they proposed a free-standing mast that would convert to a self-climbing set-up as the job progressed.” according to Rosendale.
Southwest chose one of their KVM 39X generation 2 detachable booms for the project for several reasons: The 114-foot reach of the 4-section Roll and Fold boom would reach all corners. The lightweight 12,890 pound boom could be flown to the mast by a hydraulic crane that was temporarily on-site to erect the tower crane. The free-standing configuration enabled the placing boom to pour all of the concrete in the projects early stages.
For set-up, a six-foot mast with forged flange was incorporated into the building’s foundation. “We placed the caissons first, foundations walls, the slab on grade, core walls, columns and decks from the free-standing mast,” explains Rosendale. “The Roll and Fold placing boom was extremely effective at reaching in close to the mast when the boom was at a higher elevation than the pour.” The boom placed several floors around its free-standing set-up. “When it was time to raise the boom and mast we were able to unbolt the flange connection, engage the self-climbing feature and raise it in no time.” The mast continues to self-climb supported by floor frames in the decks.
Rosendale credits the help of Schwing’s separate placing boom specialist, Jim Dickerman, with the company’s success with this method of placement. “Whenever we are trying something new, Jim is available and will find solutions to help with equipment installation. He continues to be a great help in engineering some of these unusual configurations.”
A similar set-up to One Lincoln Park was recently applied to a project that Southwest is pumping in Aspen. With property going for nearly $45 million an acre, developers build right to the lot lines. “There is really no place for any of the subcontractors to stage their equipment on the site,” Rosendale said. Even though this condo will only be a 70-foot high structure, a free-standing separate placing boom was called for because the building is tucked into the side of the ski mountain further restricting access.
The Generation 2 detachable 39-meter boom was chosen for its ability to reach the entire pour area and is currently placing slabs and foundation walls from a 39-foot free-standing mast. Schwing’s Generation 2 technology allows for the lightest weight to reach ratio of any detachable boom in its class which also allows it to be mounted on a maneuverable, and economical, three-axle truck. The boom will be transitioned into a slab supported mast and the tower crane will only need to raise it five times to top out the structure. The lightweight advantage of the boom is appreciated by the contractor. The weight advantage is made possible by separating the powerpack and reservoir from the boom when lifting.
Pouring in the mountains in winter has placed additional strain on the pumping crew. “We are constructing the most concrete intensive part of the building at the toughest time of the year due to weather,” Rosendale commented. Most of the pours are tented and heated to 70-degrees in the below zero temperatures.
Success with Separate Placing Booms
The emerging popularity of separate placing booms in Colorado has positioned Southwest as a leader for concrete placement at upper levels. “Most people see the advantages of a separate placing boom for high rise construction,” notes Rosendale, “While that is true, we have found that it is just as valuable down low at the very beginning of a project.”