Rocky Flats

Site Decontamination and Demolition (2001 – 2004)

Prior to ceasing operations in 1989, Rocky Flats had been a nuclear weapon component manufacturing facility for nearly forty years. Four decades of processing plutonium, uranium, beryllium and other hazardous materials had left the site’s facilities, soils and groundwater severely contaminated. Now owned by the US Department of Energy and designated a Superfund site by the US Environmental Protection Agency, the Rocky Flats Environmental Technology Site is being remediated by Kaiser-Hill Company with the help of MACTEC and several other subcontractors. Final site closure is scheduled for December 2006, after which the site will be converted into a national wildlife refuge.

MACTEC’s primary role in the cleanup was the decontamination and demolition (D&D) of several onsite facilities. We also developed, implemented, and maintained the project’s Radiological Protection Program (which included all radiological engineering and controls), Health and Safety Plan, Quality Assurance Plan, Demolition Plan, and associated training programs.

The first step in the D&D process was to dismantle facility components such as equipment, process support systems, safety systems, electrical systems, utilities, piping, interior partitions, interior concrete walls and slabs, and concrete masonry unit walls. To dismantle and remove the contaminated piping systems, we used small equipment inside the buildings, thus minimizing human exposure. This resulted in a time savings of three months and a cost savings of approximately $400,000.

Once dismantlement was complete, the walls, floors, columns and ceilings of the facilities were decontaminated using a hydrolasing process. The process employed a fully encapsulated and automated ultra-high-pressure water system to completely remove coatings, surface and subsurface contamination, and structural material. The supersonic water jets could be adjusted to break apart surface materials (without damaging the surface) or to disintegrate subsurface materials. Once separated, the contaminated materials were immediately vacuumed and directed to an onsite wastewater treatment system.

This system saved our client nearly $5 million by treating and recycling the contaminated wastewater instead of containerizing and transporting it for disposal. The system included two parallel units—each with a processing capacity of fifteen gallons per minute—that operated independently with separately adjustable processing rates, allowing one system to undergo maintenance and/or repair while the other continued processing. In all, more than one million gallons of wastewater were recycled.

After decontamination, the facilities had to be demolished and removed. During the demolition process, the use of heavy equipment inside the buildings, along with a combination of air handlers and dust suppressors, kept airborne radioactivity levels well below derived air concentration (DAC) guidelines. This saved our client money by eliminating the need for anti-contamination clothing and respiratory protection.

Exceptional Radiological Controls and Methods Safely Executed for Infinity Room

The most highly contaminated facilities at Rocky Flats were the Building 771/774 complex and Room 141. Classified as the site’s most hazardous building, Building 771 had served as the primary plutonium production facility during the plant’s operative years, while Building 774 had been used to treat the radioactive and non-radioactive wastes generated in Building 771.

Room 141, also known as the “Infinity Room,” was originally designed as a vault for nuclear weapon components and was later converted to a pump room for plutonium processing. During routine operations over thirty years ago, the pumps failed, and the room became contaminated at levels higher than instrumentation could measure. As a result, the door to the room was welded shut, and the room remained sealed for over three decades.

During initial entries into the room, airborne radioactivity levels exceeded one million DAC, surface level contamination exceeded one billion disintegrations per minute per 100 cm 2 alpha, and dose rates measured to 40 millirems per hour from Am-241 contamination. To contain these high levels of contamination, we used concrete overlay on the floor, along with pump pedestals and spray fixative for the walls and ceilings.

Because the room was originally designed as a vault, its twelve-inch-thick concrete walls contained considerable steel reinforcement. The walls were cut horizontally using a diamond wire cable saw, pushed over or lifted to a lay-down area, size-reduced, packaged, and bound for transport to the Waste Isolation Pilot Plant, where the debris was entombed in salt caverns. After removing Room 141, we completed under-slab characterization and soil decontamination on the site where the facility had stood. The entire process was accomplished with less than 20 mrem external exposure and approximately 100 DAC airborne exposure.

Despite significant hazards and varying levels of contamination, we and our subcontractors completed this 34-month project with a perfect safety record. Through the National Safety Council’s Occupational Safety/Health Award Program, the Council presented us with a Perfect Record award in December 2004 for working 517,562 hours without a lost-time incident.

For more information about the Rocky Flats Closure Project, please visit http://www.rfets.gov/doe/.