Breaking down big demo jobs

Photos courtesy of Jackson Demolition Services

Situated at the confluence of Baker Creek and the Mulberry Fork of the Black Warrior River in Parrish, Alabama, Southern Co.’s retired Gorgas Electric Generating Plant, better known as Plant Gorgas, presented Jackson Demolition Services with several obstacles to overcome in one of its more challenging projects.

“The original power plant had been around for almost a hundred years and had been a staple in the community,” says Mark Ramun, vice president of industrial services for Schenectady, New York-based Jackson Demolition.

In operation since 1917, the plant was shut down in 2019 in response to clean energy initiatives the company sought to meet when unit Nos. 8, 9 and 10 were decommissioned.

Jackson’s job was to take down these units, which once produced a total of 1,166 megawatts of power. In addition to taking down the power generation structures, including the boiler and turbine buildings, Jackson had to remove two smokestacks, one 250 feet tall, the other 750 feet tall, as well as nearly 250 other structures—some in the river and over the creek. From a technical standpoint, the scale of the project was nothing new to Jackson Demolition, Ramun says.

“Challenges bring out the best in our team, and we knew from day one that this project was uniquely challenging,” he says.

Not only was the site nestled between a protected body of water and a river, but it also was bounded on the opposite side by a private cemetery that couldn’t be disturbed. Additionally, the existing transmission and distribution stations were to remain operational. For those reasons, Alabama Power Co., a subsidiary of Southern Co., requested that those 250 assets on the 1,200-acre-plus site be dismantled rather than demolished.

“The client’s project management team had previously demolished two smaller units at this site, and they wanted the larger units to be dismantled in the safest manner possible,” Ramun says. “We felt strongly that explosive demolition would provide the best solution, so we gave them some options.”

Jackson submitted two bids for the project: the base bid to dismantle all structures and an alternate proposal that included explosive demolition of select structures. Bids for the job were submitted in February 2020, and the project was awarded in May 2020.

From great heights

Safely bringing down the 750-foot chimney was one of the trickier parts of the process at Plant Gorgas, Ramun says. The chimney was surrounded by obstructions on all sides in its original configuration, including high power lines, the river, creek and the private family cemetery on the north side. Jackson decided to remove the top 400 feet of the chimney robotically and then blast the remaining 350 feet using explosives.

Jackson took on Pullman Services, a Columbia, Maryland-based chimney specialist, as a subcontractor to help dismantle the taller chimney. The company, which specializes in power generation infrastructure, used a robot to gradually dismantle the stack from the top down. The robot reached out to the wall of the stack and systematically tore it down along the edges, dropping the concrete into the center of the stack.

The first phase of the chimney removal took several months to complete because the reinforced fiberglass plastic liner was much thicker than expected.

“The liner had to be removed by hand before our team could install the robot to dismantle the concrete chimney,” says Josh Kelly, corporate health, safety and environmental director for Jackson Demolition.

The whole process took Pullman just over nine months to complete.

Once the spider robot chewed up the stack and got the height down to about 350 feet, Jackson safely demolished the remaining chimney in an explosive felling conducted in February.

Preparing for the big bang

Dismantling the boiler buildings that housed the generators and turbines was time-consuming, and planning the blast required detailed engineering to get the 200-foot-tall buildings to fall in the right location. Any error would have endangered critical assets, potentially leaving area residents temporarily without electricity.

But, before anything could be imploded, preparations of the building and protection systems needed to be complete. Jackson removed the turbine buildings first to access the 45-foot-deep basement. The company installed a ramp to the basement level and proceeded to remove equipment and materials from underneath the boiler and turbine buildings.

“We had six to eight machines and over a dozen burners working in the basements at any given time. Our staff worked carefully in tight quarters to ensure everyone’s safety,” Jackson Demolition Services Project Manager Terry Polena says.

Jackson built up protective debris piles between the buildings and structures to remain, in addition to high-capacity netting systems along the building’s south side at the fourth and ninth floors where explosives were to be placed. Jackson worked closely with demolition blasting specialist Controlled Demolition Inc. (CDI), Phoenix, Maryland, to engineer and execute the explosive felling.

CDI designed the blast to drop the boiler buildings into their own basements, minimizing vibrations and flying debris, while directing the selective catalytic reduction (SCR) building on the west side of unit 10 to fall to the northeast and the 250-foot-tall chimney to be felled to the west.

Some of the columns at Plant Gorgas were so thick that explosives wouldn’t bring them down alone, so Ramun says workers used torches to shave down the columns prior to installing the explosives.

“The reality is, we worked in that building for a year before we could put explosive material in it,” Polena says.

The boiler building, SCR building and shorter stack were safely imploded in September 2021.

Working over water

Another challenge on this project was removing a 60,000-square-foot storeroom building from over Baker Creek, Ramun says.

The precast concrete storeroom building was built over the water on more than 480 batter piles. These piles needed to be removed to the mud line without any debris falling into the water.

Jackson Demolition subcontracted Veit Co., a specialty contracting and disposal company based in Rogers, Minnesota, to remove the storeroom building.

“Veit has a marine demolition group that was able to perform work in and over the water,” Ramun says. “Bringing Veit in for the marine elements of this project allowed our teams to press forward on multiple aspects of this project at once to keep pace with an aggressive project schedule.”

Veit dismantled the storeroom in a systematic fashion, sawing the concrete floors and foundation beams into manageable pieces that were removed by crane to expose the piles for divers to remove from the water.

Veit also removed a 450-ton barge unloader in the river that required underwater demolition work, as well. For this work, divers used wire rope concrete saws to cut steel and concrete pylons into smaller segments, which then had to be removed by crane in light of their weight of approximately 40,000 pounds apiece.

Wrapping it up

While the COVID-19 pandemic had a significant impact on most business operations around the world, the Gorgas project’s overall timeline did not change. Some work was momentarily delayed and rescheduled, but no work on the critical path was affected by the pandemic.

“The client’s team worked diligently to keep the project on schedule, and our whole team was able to mitigate delays by staying focused on the tasks at hand. Nobody knew what to expect with this pandemic, and there were weeks when resources were disrupted, but there were no real showstoppers” Kelly says.

In total, Jackson reused or recycled more than 98 percent of the materials encountered—with more than 60,000 gross tons of ferrous metal, more than 4 million pounds of nonferrous metal and more than 15,000 tons of concrete, which was used as clean backfill on-site.

Additionally, Jackson and its subcontractors safely worked more than 225,000 manhours on this project without a single lost time, restricted injury or environmental issue.

The whole project team had a “partnership” mentality geared toward completing the project in a safe and environmentally responsible manner, Kelly adds.

“Everyone worked together. We took time on the front end to communicate our plans so that everyone on the team could provide feedback before finalizing our execution plans,” Kelly says. “We asked ourselves a lot of questions and whiteboarded a lot of ideas before we settled on any one approach. Everyone really worked well together on this project, and the result is a safely executed project.”

The author is managing editor of Construction & Demolition Recycling and can be reached at bgaetjens@gie.net.