Placing concrete on a jobsite almost 2 miles from civilization sounds overwhelming, but it’s all in a day’s work for Cliff Barbieri, president of Advanced Tower Services in Albuquerque, New Mexico. His company builds communication towers for TV and radio, local public safety, and the federal government throughout the U.S., work that requires pouring foundations and footers for the towers, and concrete pads for prefabricated buildings that house radio equipment and for generators.
When the project is done, “everybody only sees the tower for what's above the ground,” says Barbieri. “We try to impress on our customers when we bid that more than 50% of that tower project is below the ground.”
Business is good, but each job has unique challenges. This year, Advanced Tower Services has several projects in New Mexico and Colorado, which have vast swaths of mountainous territory far from big cities. One is on a 9,000-foot mountaintop with no roads, so crews haul water, aggregate, cement, and equipment to the jobsite by helicopter. Barbieri’s tried meeting batch trucks at the bottom of hills and hauling loads up with crane buckets, loaders, or forklifts, but “engineers don’t like those methods because of the possibility of segregation of materials. It’s not your typical back up a concrete truck to a site and start pouring like you do in town.”
He overcomes that objection with the Cart-Away Universal Batching Equipment, or C.U.B.E. Made by Cart-Away Concrete Systems Inc. of McMinnville, Oregon, the 1.5-yard-capacity mixer is larger than other portable mixers but light enough to load onto a flat bed or small trailer and move around with a high reach lift. Customers have placed them miles down into mines and on barges to pour piers on islands.
“By being able to batch it on site, we’re getting fresh concrete in the hole right away,” says Barbieri. The portable batch plant and mixer has a 36-inch-by-120-inch sand and gravel conveyor on top that can be loaded by a skid steer. The belt discharges directly into the mouth of the mixer.
Advanced Tower Services recently built a microwave tower on White Sands Missile Range in New Mexico. It was on a mountaintop with a long access road far from a paved road. The crew had to navigate a 6-mile climb up an average 12% grade. Not an easy task.
Here’s how the project unfolded.
Days One, Two, and Three
Haul all dry aggregate and cement in super sacks, water, water pumps, C.U.B.E., and steel tower components to the top of the mountain. The location’s too steep and treacherous for a dump truck, so Barbieri uses an old Army 2½-ton 6x6 cargo truck.
While one crew hauled in the materials, another dug out the foundation – 5 feet deep and 20 feet square – using track hoes with hammers and breakers. Excavation took about two-and-a-half days because of all the rock.
The foundation crew starts tying rebar, placing forms, and getting the anchor bolts for the tower set. Then they configure the batch plant and get the water trailers filled, the pumps running, and all material set up for the pour.
Sometimes things go sideways. “We have to be prepared for equipment breakdowns or if something else goes wrong,” says Barbieri. “We may have to do a quick repair on site or bring in a mechanic. Most of our guys are pretty mechanical so they can fix most stuff on the fly.” This project ran smoothly.
Days Five and Six
On the day of the pour, the crew goes in as early in the morning as possible to start batching concrete.
The C.U.B.E. mixes 1.5 cubic yards at a time and this job required 22 yards. “We had to pour monolithically because the engineers didn't want any cold joints,” Barbieri says. “We had some delays that morning getting some prep work done. Then it took us about 12 hours to mix and do the pour all on site.”
Barbieri has found the optimal crew size is eight members. “That enables us to keep the batch plant up and running while we have other guys working in the foundation and supplying the concrete to them so they can place it.”
Because most projects are in areas with a lot of freeze-thaw, Barbieri uses an air entrainment admixture. In some cases, he also adds a retarding plasticizer to allow more workability and to allow for the time it takes to make batches on site.
A couple days later, they'll strip the forms, backfill the excavation, level the site, and start erecting the steel tower, which comes prefabricated from the manufacturer in a knockdown configuration. Barbieri’s team assembles the sections on site and then erects the tower.
In an interesting twist, Advanced Tower Services is having its busiest year ever, mostly because of obsolescence. Using a crane, or on occasion gin poles or rigging techniques, Barbieri’s team removes the towers and jack hammers out the foundations.
“For the last 30 years or 40 years we’ve been building towers and now we’re taking them down,” he says.