The Sweet Winds of Change
The Sweet Winds of ChangePutzmeister 32-meter boom pump handles challenging concrete mix to help construct wind turbines within leading Texas market.
STURTEVANT, WI (July 30, 2007) – In the quest for an unlimited source of energy, man has turned to one of the oldest – wind. The American Wind Energy Association has a vision of wind energy supplying 20 percent of America’s electricity needs by 2030. That’s a big leap forward, as wind is presently less than one percent of the total U.S. electricity generation.
Although wind is only a small part of today’s energy sources, it’s big in Texas. Recently surpassing California, Texas took the lead in wind capacity production at 2,768 megawatts (MW) for 2006. This equates to one-quarter of the total U.S. capacity, which is enough to power more than 700,000 average American homes. Texas can also boast that almost a third of the U.S. wind generating facilities are being built in the Lone Star State today, and 990 MW more are proposed for construction there.
“The growing number of wind farms means big business for Texas construction, and every contractor wants in on the action,” says Frank Ontiveros, general manager at Action Concrete Pumping in Grand Prairie, Texas.
A “Sweet” Market
Action, relying on their Putzmeister BSF 32-meter truck-mounted boom pump, recently placed more than 26,500 cubic yards of a “hot” and challenging concrete mix for a wind farm near Sweetwater, Texas. The specific project was Phase IV of the Sweetwater Wind Farm electric generation facility development for Sweetwater Wind Power, LLC. It was completed under the capable direction of the Mortenson Construction’s Energy Group based in Minneapolis, Minnesota – a leading construction firm within the renewable energy industry.
“We saw the market’s potential a decade ago,” says Brent Bergland, director of business development for Mortenson’s Energy Group, “and since we already had the core competency in our industrial market sectors, we entered the market in 1998 by constructing our first utility scale project.”
Today, Mortenson has built more than 45 of these green power facilities starting to dot the U.S. landscape. Plus, they have even more projects underway throughout the U.S. that presently include 10 wind farms in nine states.
A Foundation of Support
For the Sweetwater project, Mortenson managed three phases of the six-phase development. Overall, their project scope included erection of wind turbines (previously known as windmills) along with building roads, foundations, collection systems, a transmission line and a substation. For Phase IV, Mortenson was specifically responsible for the infrastructure to support 135 69-meter Mitsubishi turbines. Each turbine is capable of producing one megawatt of power that can provide electricity for between 250 — 300 average American homes.
Action’s role was to pump the structural concrete for each turbine’s mud mat, foundation and pedestal. The octagonal foundation required concrete to be pumped at a shallow thickness along its sides, while increasing to a greater thickness at its center. It resembled a shallow pyramid when viewed from its side. Centered atop the foundation was a wide pedestal, which required concrete to be placed within its tall, circular shape.
“It was absolutely critical that each foundation and pedestal support a giant 226-foot tall turbine,” says Tony Baeza, Action’s co-owner, “so everyone associated with the job was very particular about the concrete’s strength and its precise placement.”
“Fundamentally, all wind turbine construction requires a similar concrete placing approach,” says Rick Ortiz, Mortenson’s project manager. “However, the concrete specs differ on each project, being dictated by the size and type of wind turbine, along with the seasonal temperatures during concrete placement.”
In Texas, it’s typically hot. As heat can quickly cure concrete and clog pipelines, the mix specified was a “hot” 5,000-psi mix with plasticizers. The pedestal additionally required the mix to meet air entrainment requirements, which further added to the complexity of the concrete and made it difficult to pump. Typically, crews had 45 minutes to work with the concrete once placed; however, with the air entrainment spec, this turned into a limited 15 minutes before the concrete started curing.
“The concrete was an especially tough mix with its four-inch slump, and other brands of pumping equipment had difficulties placing it on various wind farm jobs throughout Texas,” says Ontiveros. “Fortunately, we had the opportunity to show what our Putzmeister boom pump could do, and it pumped the unforgiving mix without a problem.”
“It’s really a learning curve and a timing issue with the specific concrete mix we engineered,” says Rick Ortiz. “Everything has to be set up perfectly so we’re ready to pump when the concrete arrives. If anything delays the process, the mix changes its slump, which then makes it tougher to pump. Since the specs don’t allow us to add water, the pumping equipment is then forced to handle some rather difficult concrete.”
“However, Action and their equipment did an outstanding job pumping the mix and meeting the project’s demands,” adds Rick Ortiz. “As a result, we finished the project on time and within budget.”
The specialty mix was produced by Sweetwater Ready Mix Concrete Company of Sweetwater, Texas. Due to the critical mix design and the job’s explicit requirements, Mortenson assisted the batch plant in updating to a computerization system that would more precisely document its batch plant tickets. Upon meeting the job’s clear-cut conditions, the ready mix supplier dispatched the concrete via its 14-mixer fleet.
The pumping company’s 32-meter boom pump was needed for its 105-foot reach to easily access the pour within the rocky ground conditions. The machine was also specified for its rugged S-Valve, which could efficiently pump the unforgiving mix. However, the pump’s high output capabilities were not put to use, as pumping was slow and methodical due to the precise concrete placement techniques required among the rebar.
“An incredible amount of reinforcing steel rebar was needed for each foundation and pedestal,” says Rick Ortiz. “Although the center had a nine- to 12-inch rebar grid, the outer edges and pedestal had a lot less space between the steel bars along with a bulkhead that we had to contend with. Therefore, these areas were more difficult to handle when placing and vibrating the concrete.”
“Plus, any variation in concrete, such as larger aggregate size, would further complicate the project,” adds Rick Ortiz, “making it difficult to even get a vibrator in these tight areas.”
As a result, each wind turbine foundation required three-and-a-half hours to pump, while it took a half hour for each pedestal. Two foundations and two pedestals could be completed in a day.
Wind farms are often constructed in the “middle of nowhere”, and Sweetwater was no exception. Even roads had to be built within the job site’s 37-square mile area. With the project’s remote location 180 miles from Action’s facility, the boom pump remained on-site each night while the operator camped at a nearby RV park.
Due to far travel distances to the job, a backup pump was also required on-site during all pours in the event of an equipment malfunction. This pump offered added insurance; as once started, each foundation and pedestal had to be completed during a continuous pour to maintain structural integrity without cold joints. Therefore, a 32-meter roll-and-fold boom pump sat on the sidelines ready to pump, but it was never needed.
The secluded site also made concrete delivery a complex task. With a batch plant 35 miles away from the project’s front gate and a job site covering another 37 miles, a ready mix truck’s journey to a pour could take up to an hour. Any unpredictable occurrence that delayed concrete delivery, even as trivial as a flat tire on a mixer, could wreak havoc with the mix design, the pump and the crews vibrating the “hot” concrete while waiting for more.
In addition to the concrete pumping happening on the ground, helicopters provided valuable assistance from the air, providing valuable assistance. Due to the site’s isolated location, helicopters provided evacuation training sessions in the event of an emergency. They were also used to help pull 22 miles of transmission lines.
One Done, Lots More to Go
Concrete placement for the fourth phase of the multi-million dollar Sweetwater project started in September 2006 and finished in January 2007. Later this fall, Mortenson and Action will again team up to handle more Texas projects.
On future projects, the trend is for taller turbines with greater output. This combination necessitates larger foundations and greater concrete quantities.
“As each turbine’s foundation will be larger in size, we’ll be relying on our 36-meter for its longer 117-foot reach,” says Baeza. “Plus, we again expect to pump the challenging concrete mix without any difficulties.”
Co-owners Tony Baeza and Jaime Garcia remain loyal to the Putzmeister brand. The cousins started Action Concrete Pumping in 1994 with the purchase of a pre-owned 32-meter boom pump. Today, the company has grown to 14 units operating from two strategic locations in Dallas and El Paso, Texas.
Whichever Way the Wind Blows
Deemed an attractive energy market, wind power has been the second largest source of new U.S. electricity generation for two years in a row – trailing only natural gas. U.S. wind power capacity increased 27 percent in 2006, and it is expected to grow an additional 26 percent in 2007. Could wind be the next major wave in energy generation? Will “wind superhighways” the result? The construction market can only hope.