Imploding 150 missile silos along the Red River Valley in eastern North Dakota requires precise timing and the cooperation of several agencies to ensure the project is completed safely and on time.
The first silo was imploded on Oct. 6, 1999 near Langdon, ND, close to the Canadian border. Before the ground froze last fall, 13 more were imploded by Veit & Co. Inc., Rogers, MN.
In all, 150 silos have to be imploded by November 2001, as is required by the Strategic Arms Reduction Treaty, which calls for the dismantlement of some missile sites. The 150 missiles stood sentry for almost one-third of the last century across 11,000 square miles from Valley City in east central North Dakota to the Canadian border.
Bart Anderson, vice president of Veit & Co. Inc., said one of the challenges of the project is the magnitude, since it is spread out over such a large area. Anderson added that he had previously worked for a company that imploded 150 missile sites in Missouri and so he is very familiar with the procedure, aiding him in this project.
In 1995, the federal Base Realignment and Closure Commission decided to empty the Minuteman III missile silos under the jurisdiction of the Grand Forks Air Force Base in eastern North Dakota. The last missile was removed from its silo in June 1998 in preparation for the demolition of the silos and their control facilities, according to the Omaha District U.S. Army Corps of Engineers, who is overseeing the project. The sites range from a 30-minute to a 3-hour drive from the Air Force base.
The Corps worked with the U.S. Air Force to prepare the specifications and drawings for the $13.8 million project. The 150 silos are being imploded in three phases, with 50 silos and five missile launch control facilities in each phase, explained Larry Bringewatt, project manager with the U.S. Army Corps of Engineers, Omaha Division. Work on the second phase began this spring and the third phase will be launched in 2001. Funding is received as each phase is to begin.
Bringewatt added that the Corps previously worked with the Air Force, having put together a package in 1992 and 1993 to demolish 150 missile silos at Ellsworth Air Force Base in South Dakota, and 150 at Whiteman Air Force Base in Missouri.
However, added Bringewatt, the Grand Forks Air Force Base project is not identical to the previous projects. The Grand Forks silos were built later than the ones at Ellsworth. The generators were in a capsule underground at the Grand Forks sites, while the ones at Ellsworth were in a building that was partially out of the ground. And the top of the silos and the lids for the silos were more heavily reinforced at the Grand Forks silos.
The first step to implode the missile sites connected to the Grand Forks Air Force Base is to salvage the metal liners from the silos, which the equipment crew works on. Each of the silos is constructed with a 120-centimeter (2 ft.) steel liner plate that is surrounded by 3 meters (10 ft.) of reinforced concrete. The bottom 18 meters (60 ft) of the 27-meter (90 ft.) silos are 3.6 meters (12 ft.) in diameter while the top 9 meters (30 ft.) is 11 meters (36 ft.) in diameter. Once the metal liners are salvaged, a drilling and blasting crew drills holes into the silos, using an Ingersoll-Rand ECM 370 drill, and packs the holes with about 800 pounds of explosives to blast the silo.
Drilling takes about two days and preparation takes another day. The top 6 meters (20 ft) are blasted and the bottom 21 meters (70 ft.) remain in tact. Two 350 Cat backhoes are brought in to tear apart the debris, digging to a depth of 6 meters (20 ft.).
The preparation includes torching plate metal and doing scarf cuts so the metal implodes properly, Anderson said. Since concrete is poured against the steel, a scarf cut is used to put a groove in the metal so it tears away.
The launch control facilities are basically underground bunkers, which are two capsules 18 meters (60 ft.) below grade, Bringewatt said. One capsule had mechanical equipment, air handling equipment and a generator, while the other was the living space with the control equipment.
Safety issues are always a concern when explosives are involved. For the drilling crew a safety cage was built that fits over the top of a silo hole to keep workers from falling 27 meters (90 ft.). All the steel cutting is done through lead paint and so is done under respiratory supplied air.
Since some of the sites were close to wetlands, environmental concerns were taken into consideration and steps were taken to ensure wetlands were not impacted, according to the Corps. Bringewatt added that steps were laid out on how to grade the area to maintain the existing drainage. Permits were obtained from the state of North Dakota to handle any water discharge. Some of the sites were full of water and storm water permits were obtained to pump the water out of the site. All the water was tested before it was pumped.
Because there was living space in a one-story building above ground and in a capsule, sewage was contained in lagoons. Most of the lagoons were dry but some contained sludge that had to be sampled and tested as part of the closure. No problems are expected with the sludge but if there should be a problem, environmental rules take over as to how the sludge will be handled.
There is one launch control facility for every 10 silos. Some of the deeper lagoons were abandoned while others were removed, Bringewatt added, all of which was done according to the U.S. Environmental Protection Agency standards and state environmental standards.
Anderson said that 180, 4,000-gallon to 15,000-gallon diesel storage tanks for the emergency generators had been installed just prior to the arms reduction treaty and so were removed and sold to local farmers and gas stations.
After the implosion, which sends chunks of concrete into the air about 100 feet with a muffled boom and a dust cloud with debris, the rubble goes down into the silo and a 46-centimeter (18 in.) thick concrete cap is placed on top of the silo for 90 days. This 90-day observation period provides Russians with an opportunity to check the status of the project by technical means, so they are confident the dismantlement and implosion have been complete by the date specified in the treaty.
A 99-metric ton (110 ton) silo closure door is buried 3 meters (10 ft.) below the surface in front of the destroyed silo. “The lid doesn’t shatter very well so rather than trying to shatter it they just bury it,” said Bringewatt.
So far the entire project is on schedule. All the implosions are expected to be finished by July 30, 2001, which will leave 90 days before the last step is started at the beginning of November 2001. Then, a third crew from Veit & Co. will begin backfilling over the sites and re-spread some gravel and seed some grass. Backfilling will be done with the materials that are on site.
A fence will be left around the area to define the land, which will then go through a reclamation process where area residents will have a chance to purchase it from the government. Since all the proper steps will be taken to meet environmental codes, the land can be used for basically any purpose including building or grazing, Anderson said.
Today's top stories
