At 10:29 a.m. on June 3, Dykon Blasting Corp. set off a warning siren and then pressed a very important button. It sounded like the game buzzer at the end of a Hornets game, but this siren signaled the end of an era.
Thousands of spectators watched as 52 shaped charges exploded, shearing through the steel beams of the Charlotte Coliseum. After 13 seconds, the structure, located on 170 acres (69 ha), fell to the ground in a giant cloud of dust and settled into the 50 ft. (15 m) deep coliseum bowl. The crowd cheered, though there were some tears as well, especially from those who held fond memories of the coliseum.
Some spectators wore Hornets colors in memory of the basketball team that played there for 14 years.
“It was truly a family event,” said Stephanie Kegley of CST Environmental. “Adults, children, even the family pets came out to see the coliseum’s final performance.”
The demolition had happened half an hour late because of inclement weather.
“The cloud coverage actually determined when we were going to push the button,” Kegley explained. “They had to delay it to ensure the clouds were going to be above 1,200 feet to minimize the shock.”
If the contractors had not waited, a wave of energy and sound could have fanned outward from the implosion and broken windows or caused other damage to surrounding buildings.
“The shockwave is like a water hose,” Kegley explained. “If you put your hand in front of the water as it comes out, it fans to all sides. When cloud coverage is below 1,200 feet, it reacts like the hand in front of the hose. The wave from the shock fans out instead of up toward the sky.”
A tropical storm, Barry, loomed overhead, causing low cloud coverage, and threatening to disrupt the planned implosion, but the coliseum was determined to take its final bow that day. CST and Dykon watched the clouds and picked the perfect time to press the button with minimal shock.
“Demolition is a science,” Kegley said, “a process of calculations and simulations to get the correct results.”
One part of the science is choosing the right explosives. While most demolitions implode concrete structures, Charlotte Coliseum had a steel frame. To cut through the steel columns, Dykon used shaped charges, which are like small rockets. All their force is pointed in one direction. Placing shaped charges requires great precision, but they can cut through steel, iron and other dense materials.
After the implosion, CST and Dykon performed safety checks on the building.
“Even after it implodes, how do you guarantee that all the charges went off?” asked Kegley. “Dykon has cameras set up. They have equipment that counts those charges, so it’s a very technical process. You don’t think about it at the time, but you can’t have crews going in there and cleaning up if all the charges haven’t gone off.”
Some fans were sad to see the coliseum fall, but a part of the great building will remain on-site.
“We’ve been able to recycle approximately 80 percent of the material,” said Mark Lee, demolition operations manager of CST. “We’re crushing a lot of the concrete on-site. There’s a hole about 60 to 70 feet below grade. We’re filling that 60-foot hole with crushed concrete and with some of the soil in the area.”
Part of the building will remain on-site in a dramatically different form. The recycling is important to CST Environmental.
“You have to think about the end result [of this type of project] from the get go,” said Lee, “which is why we chose to do an interior gut.”
The interior gut removed drywall, carpet, windows, insulation and other materials that would have mixed with the concrete and made things messy had CST not removed them.
“The cleaner we can keep the concrete by separating it from the C and D debris, the easier it is to sell,” Lee explained.
CST used crushers, excavators, track loaders, Bobcats, dozers, Nye grapples, Nye concrete processors, lifts, LaBounty MSD 100 second member shears and Cat MP 30 third member shears to complete the job.
“You have to make sure the shear is capable of handling the size of the material on the project. There are 18-inch beams with inch-and-a-quarter flanges and the LaBounty shear will cut through that. That allows us to process the steel a lot faster, so we can ship it off to a recycler,” Lee said.
CST also is preparing the land around the coliseum for its next generation of inhabitants — the City Park buildings. City Park will be a 170-acre development with residences, stores, office space, a hotel and a 3-mi. trail for walking, running and biking.
To prepare the site, CST graded and compacted approximately 150,000 cu. yd. (115,000 cu m) of soil around the project hillside, evening out the land, and hired a subcontractor to clear trees around the coliseum.
“There were about 15 to 20 acres of highly dense forested area,” Lee said. “A sub came in and logged it all and cleared out the stumps. Then we had to do an erosion control to prevent sediment runoff and storm water pollution.”
CST is the general contractor for the demolition phase of the project. Pope & Land Enterprises Inc. of Atlanta, Ga., hired CST after purchasing the coliseum from the city in January 2006, when the Charlotte Bobcats left for their new uptown home, the Charlotte Bobcats Arena.
CST expects to finish the project in early October.
“All in all it’ll be a good project [for the community]. A lot of people were sad to see it go, but the redevelopment will be great,” Lee said. CEG