Waste Encapsulation

Avanti grouts are used extensively in stabilizing soils and creating impermeable barriers to stop the migration of hazardous wastes, including radioactive materials.

Below are a few examples:

In Pennsylvania, Rembco used grouting to contain oil leaking under an oil refinery's sea wall. The concrete wall had been constructed on top of old wharf piling. Over time, tidal action caused erosion, resulting in leakage at the wall's base.

"At high tide," says Dick Berry, "water seeped under the wall, picked up oil, and as the tide went out, carried the oil into the Delaware River. Grouting with a combination of time-release bentonite and cement-based grout with chemical grouts as set control agents solved the problem along approximately 550 feet of sea wall."

Grout was pumped through pipes installed behind the sea wall by wash boring and driving pipes to positions below the tide's lowest level. Spot leaks from joints and pipe penetrations were sealed with urethane-based grout.

"If you can lock any radioactive material away long enough," he says, "it degrades to a point where it no longer is harmful."

At Tennessee's Oak Ridge National Laboratory, Rembco used three types of grout to address leakage of low-level radioactive and chemical materials buried in waste trenches. Cement based, microfine cement based, and chemical solution grouts were applied to encapsulate contents of the trenches, reducing leaching of contaminants to the nearby stream to an almost insignificant level.

"This was accomplished with little hazard to personnel by driving sleeve port grout pipes, instead of drilling them in, and controlling overflow water from the trenches during operation," says Berry.

The cost of the program was $2.4 million, says Berry. An additional $1.6 million was spent on monitoring, radiation safety, engineering and field administration. The $4 million total for both was under the project budget by nearly $1 million and was about 10 percent of the $40 to $50 million which would have been required for the next-best alternative.

"The economics were driven," says Berry, "by the fact that these four trenches were responsible for about 90 percent of the polluting leakage into this particular stream."

On another project at Oak Ridge, grout stopped leakage of radioactive waste from a contaminated wastewater pond. Escaping material was entering a storm sewer system and flowing into a surface stream.

A cured-in-place liner placed inside the sewer failed to stop the radioactive drainage with contaminated waste.

"Grouting outside the pipe with acrylic-based chemical water-stop grout corrected the leakage, retaining waste in the pond," says Berry. "The project was handled safely and at very low cost."

At an old mine in Virginia, coal fines broke through clay seals placed along old underground drifts, and began contaminating the adjacent river.

"Depth of the fines from an impoundment dam had reached about 30 feet above the leaking zone when the breach of the seals was discovered," says Berry. "By setting casing from a bench above the leaking areas, the seals were renewed by grouting with a time-release bentonite material. This allowed the facility's washing plant to stay in production while the fix was accomplished."

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