Building a Concrete Bunker

In a secluded mountainous location within the Carolinas, advanced features of Putzmeister truck-mounted concrete boom pumps are being utilized to pump concrete for a unique application -- an underground bunker to be used should catastrophic disaster strike in 2012 as predicted by Nostradamus.

The large 13,000-square foot bunker is designed to help its occupants escape the major effects from nuclear blasts and radioactive fallout as well as provide protection from natural disasters. The bomb shelter will be used by its anonymous owners for emergencies only, while hidden near the couple's primary residence for quick evacuation.

To ensure the greatest resiliency, the bunker is being built below the earth's surface with concrete, deemed the strongest material for its long-lasting durability. To construct both the underground fallout shelter and its three-story lookout tower in the most time and labor efficient manner, three boom pumps are placing 3,900 cubic yards of concrete to finish the $3.5+ million project by 2011. This targeted completion date is two years after the project's May 2009 start date and one year prior to Nosterdamus' 2012 warning.

The Chosen Ones
Responsible for the unusual project's construction is general contractor Baxter Norris Construction, Inc. of Zionville, North Carolina, and concrete contractor Ocmulgee Concrete Services, Inc. of Morrisville, North Carolina. Chandler Concrete of Burlington, North Carolina, is supplying the concrete, and HFK Corporation (HFK) with locations in Burnsville, North Carolina, and Hollywood, Florida, is providing the concrete pumping services.

To handle precise concrete placement, HFK is putting the compact size of their three-axle truck-mounted concrete boom pumps to the test. This includes a 32Z-Meter, first on the site to handle the footings, and also a 36Z-Meter. However, the bulk of the concrete is being pumped with a 40Z-Meter.

"We specifically purchased a Putzmeister 40Z-Meter for this project because the model offers long reach and an ultra-lightweight design of less than 56,000 pounds (25,400kg), not to mention it's mounted on a more maneuverable three-axle truck," says HFK's vice president Frank Kahn Jr.

"A three-axle truck was a 'must,' because just getting to the job site requires navigating a mile-long gravel road up a steep mountain that has switchbacks with three-point turns," says Kahn Jr. "A four-axle vehicle just wouldn't be able to make those hairpin turns."

Kahn Jr. adds, "Once on the job site, there was limited space so we needed the machine's tight turning radius and compact outrigger footprint to safely set up the boom pump."

Another important feature was the 40Z's long 115-foot two-inch horizontal reach. Kahn Jr. notes, "With the longer reach of the boom pump, we could access all areas of the pour and avoid the labor of dealing with extra delivery line."

Non-Stop Pumping
The first major concrete pour was the footings that were connected to eight massive holes. The process required an exorbitant amount of concrete as the largest of the eight holes was 20 feet square and 10 feet deep.

Having started at seven o'clock in the morning, HFK continuously pumped concrete for 18 hours, as over 750 cubic yards of concrete, more than double the amount initially expected, had to be pumped non-stop to avoid cold joints. Adding to the job's complexity, the restrictive job site's space allowed room enough for only one ready mix truck at a time to be discharged into the pump's hopper. This was further compounded by a one-lane gravel road, which allowed only one ready mix truck at a time to travel its extremely narrow path. Any vehicle that met another on this road would require one or the other to back down.