Ten years into a decommissioning process that will likely continue for two more decades, the Trojan Nuclear Plant cooling tower in Rainer, OR, was imploded at 7 a.m. on May 21.
Crowds of onlookers, including a large constituency of former plant employees, watched from a dock in Kalama, WA, directly across the Columbia River from the plant.
In partnership with Portland General Electric (PGE), Controlled Demolition Inc. of Phoenix, MD, spent several weeks preparing for the event.
Funded by PGE, estimated costs for the cooling tower implosion total $3.9 million, said Ariana White, PGE communications specialist. The total, which included fees for contractors, as well as security measures and other incidentals, is part of the overall Trojan Plant decommissioning budget, White said.
Implosion of the 499-ft. (152 m) tower took less than 10 seconds. Mark Loizeaux, president of CDI, called it a “textbook job,” with the tower falling into itself and leaning slightly to the south.
The subsequent dust clouds headed southeast, but dissipated quickly with no impact on nearby Interstate 5. All that remains is debris and a 35-ft. (10.6 m) wall.
Crews moved in the next day to start crushing concrete, recycling steel and tearing down the wall (which CDI officials said is not nearly as tall as they anticipated).
Explosives Bring Tower Down
Built in the early 1970s, the tower weighed approximately 42,000 tons (38,102 t), incorporated 21,000 cu. yd. (16,056 cu m) of concrete and boasted a diameter of 250 ft. (76.2 m) at the top and 385 ft. (117.3 m) at the base.
It took 2,792 lb. (1,266 kg) of nitroglycerin dynamite to take the tower down, said Doug Loizeaux, CDI’s vice president.
In preparation, the contractors used pneumatic drills to place 2,934 holes into the lower portion of the structure, in two horizontal bands. The holes were covered in layers of chain-link fence and geotextile fabric in order to control debris.
Some holes were just 100 ft. (30.5 m) off the ground, while others reached 250 ft. (76.2 m). The company used 125-ft. (38.1 m) Genie and JLG personnel lifts to do the job, along with a Grove HL50 crane for the higher holes, provided by Campbell Crane and Rigging Services Inc., based in Portland, OR.
“By the strategic placement of the explosives we were able to modify the structural integrity and turn it into kinetic energy,” said Doug.
CDI’s Oregon-licensed blaster, Thom Doud, triggered the implosion using a hand-held blasting machine.
Implosion, Doug explained, was the only logical way to take the tower down. The other option, de-building, would have taken “a lot of time.”
CDI called on Iconoc/LVI of Seattle to oversee the post-implosion clean-up. Branch Manager Reef Anderson said he expected his crew to spend approximately 16 weeks on the job. After all the rebar is removed from the site, the concrete will be crushed to a diameter between 2 and 3 in. (5.1 and 7.6 cm).
“The rebar that will be recycled is upwards of 2,000 tons,” Anderson said.
Anderson said Iconoc/LVI will have approximately eight people on the job site operating various pieces of equipment such as a Hitachi EX 700 with a bucket and thumb attachment, and EX 300 with a 5,000-lb. (2,267 kg) hammer and an EX 450 with a 10,000-lb. (4,536 kg) hammer.
They also will work with a Komatsu PC650 with an MDSI 140R shear attachment and a PC450 with a Genesis 500R shear.
Preparing for the Unexpected
Though the implosion went smoothly, CDI and PGE both had to take several potential challenges into consideration as they made plans.
Because the tower was in a seismic zone it was built with heavy reinforcement and they had to make contingencies for the possibilities of extreme wind, rain, lightening or dense fog.
Also, the Pacific Northwest is a region known for its natural beauty and strict environmental regulations, which set the bar high as far as environmental compliance, Mark said, so CDI worked closely with PGE to make sure environmental impact was minimal, if not unnoticeable.
“This is a very green project from our point of view,” said Doug. “Nothing from the [demolition] is going to a landfill.”
CDI also set off a scare charge for birds and other wildlife two minutes prior to detonation, and PGE created a .5-mile exclusion zone around the tower, including the river, highways and airspace.
And while some citizens were concerned that the implosion would generate nuclear waste, according to PGE the tower never contained radioactive material and did not contain any hazardous substances.
The Tower’s History
At one time, Trojan (which opened in May 1976) employed approximately 1,200 people and generated 1,130 megawatts of energy.
PGE sited economic reasons and a desire to find more efficient energy sources when it closed the plant in January 1993.
Decommissioning began two years later, and the plant’s four steam generators and a pressurizer were relocated to a low-level waste disposal facility in eastern Washington. The plant’s reactor vessel was transported to the same facility in 1999.
Later, contents of the facility’s fuel storage pool were transferred to concrete containers, called dry cask storage.
Today, the containers are still stored safely on the site and will remain in place until they can be moved to a forthcoming federal waste repository. PGE, along with the Oregon Department of Energy and Nuclear Regulatory Commission, keep close tabs on the containers.
Though the tower itself is gone, the 634-acre Trojan site still houses a containment building and other auxiliary structures, none of which are in operation.
Currently, the plan is to demolish the containment building in 2008.
Plans for the site’s future are still up in air, but PGE is considering several options including a new power plant or a new state park. The energy company also is building a new power plant at Port Westward in Clatskanie, OR, (15 mi. north of Trojan), set to open next year.
According to PGE, the new plant will be ultra-efficient, “generating enough electricity to power approximately 300,000 homes.” CEG