Nelson Environmental Remediation and TWI team up to provide cost-effective thermal soil remediation.
Disposing of contaminated soils in a landfill may leave a company with a clean site, but it doesn’t get rid of a possible lifetime of liability for any subsequent environmental effects. Thermal remediation can clean such soils so they can be reused onsite or for other purposes.
“When we get there, it’s contaminated. When we leave, it’s certified clean,” says Kirk Shellum, the U.S. president of the Canadian firm Nelson Environmental Remediation of Edmonton, Alberta. NER, which has been in the soil remediation business for 18 years, is now providing its thermal solution in the US by teaming up with TWI Oilfield Fabrication in Fruita, Co., (formerly Todd’s Welding).
TWI has been serving the oil and gas industry for 17 years offering manufacturing and fabrication services and wanted to offer soil remediation services. “It’s a very capital-intensive business,” says Shellum, noting it was more efficient for the two firms to work together rather than offer identical services.
NER has three mobile thermal treatment systems that it can bring to a contaminated site. Such work is usually a turnkey project, including excavation, sampling, testing through an independent laboratory, treatment, post-treatment sampling and testing, backfilling and compaction.
Shellum says thermal remediation is useful at gas, oil and mining sites to remove total petroleum hydrocarbons (TPH) from drill cuttings and contaminated soils from spills of oil or gasoline at drilling sites, refineries, bulk storage facilities and pipelines. Other candidate sites include industrial plants, military bases, manufactured gas plants, flare pits and underground storage tanks. Current NER projects include a pipeline spill and an old oil well site. TWI and NER have teamed up on several projects in Colorado.
NER has sales offices in Edmonton, Calgary, Seattle, Minneapolis and France and is negotiating on projects in Eastern Europe and the Middle East.
NER’s mobile thermal desorption systems use heat to evaporate the hydrocarbons so they can be collected and combusted. NER’s three units are sized at 20, 40 and 45 tons per hour with the 20-ton system available to customers in the U.S. With its smaller size, it is easier to transport to remote sites, such as the mountains in the western U.S.
Each unit consists of four components: control house, primary treatment, bag house and secondary treatment (thermal oxidizer). “The control house is staffed by an operator at all times to make sure everything is in balance with the temperatures in the primary and secondary treatment units,” says Shellum. The process runs around the clock.
The contaminated soil is first excavated and stockpiled near the thermal desorbtion equipment so a front-end loader can feed it into a hopper. The soil is carried by a belt to a 60-inch-diameter, 28-foot-long drum that serves as the primary treatment unit. As the drum rotates the soil, a burner adds air and heats the material to anywhere from 450 to 1,000 degrees F. The company’s largest system can be configured for higher temperatures to treat long-chain hydrocarbons.
“The first thing to come off the impacted soil is the moisture,” explains Shellum. “That becomes part of the process gas stream. As the contaminants hit their boiling point, they also become part of the gas stream, which is pulled out of the drum.”
The gasses and dust are removed to the baghouse where the dust is collected. The gasses continue to the thermal oxidizer where they are combusted at temperatures ranging from 1,400 to 1,800 degrees. Shellum says the oxidizer removes from 99.5 to 99.99 percent of the contaminants before exhausting to the atmosphere.
“There are no particulates coming from the stack, just heat and water vapor,” he adds. “There’s no smoke, all you see is heat waves.” The exhaust contains nitrogen, water, oxygen and carbon dioxide.
The dust is added back into the primary treatment drum before the soil is expelled to a mixer/cooler where water is added to bring the moisture content to about 8 percent. Depending on the level of contamination, the soil is in the drum for just five to 10 minutes.
Post treatment analysis is done to make sure the soil has been decontaminated properly. The soil is now ready for reuse and compacts very well. “It can go back into the excavation site and be compacted and we’ve completely recycled the soil,” says Shellum. He adds that NER is the only soil remediation company that guarantees its results. If the soil needs further treatment, it is done at NER’s expense.
To illustrate the viability of the soil, Shellum points out that treated soil left in a pile after treatment will have weeds growing on it within three to four weeks. “If it’s topsoil that was treated, you put fertilizer on it and you can grow anything you want. You have the same material that came out of the ground going back into the ground,” without the petroleum contamination, of course.
While the soil is clean, Shellum says NER would not recommend it for use in a residential setting simply because of the stigma of it being previously contaminated and to ensure public health and safety. How it is used is up to the customer. “It works great for backfilling a large excavation at a spill site, road base, construction fill and things like that.”
Shellum says generally the option of landfilling contaminated soil is less expensive than thermal remediation, but landfilling results in a long-term liability that most companies would probably prefer to avoid. “Landfills typically use it as daily cover over the garbage,” he says. “As it rains on that landfill, contaminants begin to seep down and become part of the leachate.” The light end hydrocarbons are released untreated into the atmosphere.
Landfills keep a manifest of all materials so they have record of companies that have provided such soil. “Anyone who puts soil into a landfill has what’s called ‘cradle-to-grave liability,’” says Shellum. “The minute there is a problem or the landfill has to close, they get a tap on the shoulder to help fund a cleanup and they pay for it a second time.”
By removing the contamination, thermal remediation “severs that chain of liability right at their site,” he adds. “They may pay us more up front, but they’ll only pay us once.”
Shellum says a typical soil remediation project will cost from $50 to $80 a ton. He estimates the final cost of landfilling is between $40 and $60 a ton. “Landfills can set whatever price they want,” he adds. That is because without contaminated soil, they would have to pay to bring in cover soil. “It’s the trucking that adds up. You also have to fill in the hole left behind by removing contaminated soil.” That means buying dirt and the associated trucking costs.
NER and TWI can provide several options for a remediation project. A turnkey project would include everything from excavating the soil, through treatment and reuse. Or the equipment can be brought in to just treat soil that has already been excavated and the customer can do their own reuse work if they prefer.
It requires six to 10 semi loads to fully mobilize the equipment, so the minimum size of a project is about 5,000 tons of soil to make it an economical option. That would require about three weeks for mobilization, setup, thermal treatment and demobilization. “It all depends on the quantity of soil,” says Shellum. “But we can give a predictable and guaranteed timeframe.”
Shellum sees a good market into the future. “I’ve been in this business since 1990 when landfills were taking all the material. Thermal remediation took off and we had a growth spurt in the 90s with underground tank work.”
There are an untold number of contaminated sites around the country, and world, still waiting for cleanup, such as many manufactured gas plants, Superfund and brownfield sites. “They’re sitting next to rivers or beautiful properties,” says Shellum. “In some cases, the regulators don’t force them to do anything. Those that seem to get cleaned up are those where someone suddenly says, ‘We need that land,’ and someone pulls the trigger to get it done.”