Robert E. Cornish
U.S. Department of Energy
Environmental Restoration Division
P.O. Box 5400, Albuquerque, NM
ABSTRACT
The Uranium Mill Tailings Remedial Action (UMTRA) Project, a 1.45 billion dollar project to stabilize uranium mill tailings and remediate structures built with them, is nearing completion. The successful completion of this project would not be possible without exemptions and variances from a number of federal regulations. The Department of Transportation provided an exemption from regulations which, if followed verbatim, would have precluded the economical transportation of uranium mill tailings on public highways. The Department of Energy (DOE) provided exemptions from parts of 10 CFR 835 regarding radiation dose assessments for radon and radon daughters, and radiological controls on tailings in inaccessible spaces in vehicles. The Environmental Protection Agency has allowed a variance involving the measurement of radon flux to the atmosphere from completed tailings disposal cells. In addition, it was necessary to use liberal interpretations of certain DOE Orders (under the process called "graded approach"). This paper describes how these measures eliminated many costly and wasteful actions that would have been required by a literal interpretation of the regulations. Other remediation projects should avail themselves of opportunities to alter their regulatory environment.
INTRODUCTION TO THE UMTRA PROJECT
Congress created the UMTRA Project with the passage of the Uranium Mill Tailings Radiation Control Act (UMTRCA) of 1978. This act gave the Department of Energy (DOE) the responsibility for remediating 24 uranium mill tailings piles, and associated "vicinity properties", in ten states. The "vicinity properties" are structures built on or with tailings, or open land contaminated with tailings. The UMTRA Project is regulated by the NRC; the EPA has virtually no involvement with the project, except for some radon flux measurements that are done when each tailings site is almost completed.
Some tailings piles were stabilized in place. Others were first relocated to more favorable areas, and then stabilized. In both cases, the tailings end up in disposal cells, with clay covers, that resemble large municipal landfills. The UMTRA Project tailings piles range up to about five million cubic yards in volume. The largest tailings piles, at Rifle and Grand Junction, Colorado, were relocated. The tailings relocations have been among the largest mass movements of radioactive waste in history. The Rifle and Grand Junction projects each involved tailings movement rates of between 15,000 and 20,000 tons per day. There was one day in 1995 when the Rifle project had a record 920 trucks of radioactive material leave the site and travel down public highways to a disposal site several miles away. Such large rates of movement are economical only with rapid turnaround of the transporting vehicles at each end.
Uranium mill tailings are a sand-like material that remains following the chemical extraction of uranium from uranium ore. The tailings contain radium-226 and other members of the uranium decay chains. The decay of radium-226 produces radon gas, which emanates to the atmosphere from tailings piles. The radon constitutes a health risk to the UMTRA Project workers. The clay cover of a tailings disposal cell must be able to attenuate the flux of radon to the atmosphere. The radon flux to the atmosphere through the finished clay cover is measured to demonstrate compliance with the applicable regulation.
TRANSPORTATION
Several Department of Transportation (DOT) regulations could have precluded the economical transportation of tailings by introducing significant delays in the turnaround of tailings-hauling trucks. Tailings contain sufficient radioactivity to trigger some of the DOT regulatory provisions related to the transportation of hazardous materials or hazardous substances. The DOT regulation 49 CFR 172.203 (d) requires an analysis of each shipment to determine the activity of each radionuclide it contains. There would be a substantial delay if each truck had to have a specific manifest based on an actual analysis of its cargo. Another requirement, 49 CFR 173.403, says that a "closed transport vehicle" must limit access from the top. Some environmental restoration projects have shipped contaminated earth in large metal boxes with lids, but additional time would be needed to add and remove lids.
The DOT granted the DOE an exemption from certain DOT regulations that solves these problems. The exemption, DOT-E 10594, was granted on May 28, 1992, and has since been renewed three times. The exemption allows the use of a generic description of the physical and chemical composition and radioactivity content of tailings and eliminates the need for an actual analysis of each shipment. The exemption also allows the UMTRA Project to hire tailings-removal contractors who have standard earthmoving and hauling equipment, such as dump trucks. The use of standard trucks rather than specialized boxes with lids resulted in a substantial cost savings. The exemption does require that the tailings in such trucks either be covered with tarps, or sprayed with a special glue-like material to prevent tailings loss during transport. The UMTRA Project used the glue-like material in place of tarps on most of the tailings haul from the Grand Junction, Colorado, tailings pile. Elsewhere, tarps have been used.
The exemption eliminated the requirement to weigh each shipment. It also simplified the labeling and placarding requirements, and modified the spill reporting requirements. The third revision of DOT-E 10594 is still being used by the UMTRA Project, and is also available to the Grand Junction DOE office for use at the non-UMTRA tailings remediation project at Monticello, Utah.
CONTAMINATION IN VEHICLES
The DOE regulation 10 CFR 835 applies to the release of potentially contaminated materials from a radiological area to a controlled area. If prior experience suggests that contamination on inaccessible surfaces exceeds specified values, 10 CFR 835.1101 (a) (2) forbids the release of material or equipment from the radiological area.
This single provision could stop the UMTRA Project dead in its tracks. The trucks used to haul tailings typically acquire some contamination in inaccessible spaces such as nooks and crannies under the trucks, and inside brake drums. The loaded trucks are subjected to a decontaminating water spray before they leave the tailings site, but this process does not result in the complete decontamination of all areas. Experience has also shown that the decontamination process itself sometimes further fixes contamination; tailings radionuclides sometimes leach into presumably porous hot parts of the engine and transmission. Such contamination may be difficult to remove by any process short of sandblasting. The contamination inside parts such as brake drums can not be removed, and can not be shown to definitely exist or not exist, without a time-consuming partial dismantlement of the truck.
The UMTRA Project has experimented with several ways to limit the contamination of trucks. Trucks inside radiological areas are typically routed on roads that are essentially clean, even though they are inside the radiological area. Conveyor belts and hopper systems were tried at several sites; such systems may enable a truck to load or unload without actually driving inside a radiological area. The conveyor belts were not an unqualified success, as they tended to jam up on wetter, fine-grained slime-like tailings. The conveyor belts also could not handle contaminated rubble from building demolition. At all UMTRA Project sites where tailings were relocated, there were opportunities for trucks to pick up contamination.
The DOE granted an exemption from 10 CFR 835.1101 (a) (2) on January 5, 1996. This exemption allows the release of tailings trucks from radiological areas to controlled areas even when experience suggests that contamination above the applicable levels exists on inaccessible surfaces.
OCCUPATIONAL EXPOSURE TO RADON
The DOE regulation 10 CFR 835 contains several requirements involving occupational exposure to radon and radon progeny that proved impractical to implement. The major problem was that the regulation presumed that it would be practical to distinguish occupational exposure to radon and radon progeny from background exposure to the same radionuclides. Several provisions of the regulation involved record keeping and the triggering of additional measurements based on this presumption. In practice, it proved impractical to separately measure occupational exposures and background.
The DOE granted an exemption from several radon-related provisions of 10 CFR 835 on February 9, 1995. The exemption eliminated the need to attempt to separately measure occupational exposures and background. In the future, background and occupational exposures will be combined, and the exemption raises thresholds beyond which certain monitoring and air sampling is required.
ENVIRONMENTAL RADON
The only area of EPA regulation of the UMTRA Project is under the National Emission Standards for Hazardous Air Pollutants ("NESHAPS") Subpart T, which provides a standard for radon flux to the atmosphere and prescribes a method of measurement to prove compliance.
Technically, the UMTRA Project has been in violation of this regulation since December 1991, since compliance with the radon flux standard was required at that time and the UMTRA Project was not yet finished. A Federal Facilities Compliance Agreement (FFCA) ideally should have been made with the EPA, but negotiations to that end broke down and a FFCA was never signed.
Several provisions of the radon flux measurement requirements proved problematic for the UMTRA Project. The worst provision is 40 CFR 61.223 (a), which says that the radon flux measurements will be made sixty days following the completion of covering the pile to limit radon emissions. A compacted layer of clay, with a carefully controlled moisture content, is used to limit radon emissions. This layer (the radon barrier) must not be allowed to dry out. Most of the UMTRA Project sites are in the "four corners" states of the southwestern U. S., where sixty days of exposure to dry air and sunlight could seriously alter the radon attenuation properties of the radon barrier. The UMTRA Project has always followed the practice of working across the radon barrier, making the radon flux measurements as soon as an area of radon barrier is completed, and then immediately covering that area with (typically) a several foot thickness of dirt and rocks. We have informed the EPA that we will not make radon flux measurements within 10 feet of the edge of the completed radon barrier, so as to limit "edge effects" that might result from the lateral diffusion of radon. The UMTRA Project should have obtained an exemption or variance from the "sixty day" rule, but none was ever obtained.
Two additional provisions of the NESHAPS regulations have caused minor problems. The radon flux measurement protocol is given in 40 CFR 61, Appendix B, Method 115. Method 115 states that measurements shall not be made within 24 hours of a rainfall, or if the ambient temperature drops below 35 degrees F. Construction at UMTRA Project sites is often completed late in the year, when temperatures are dropping. The radon barrier is often completed in late summer or autumn, when rain is likely in the southwestern U. S. The UMTRA Project requested, and was granted, a minor variance from the EPA regarding rainfall conditions during the period of the measurements. This variance allowed the measurements to proceed if there was no more than one-tenth of an inch of rain during the preceding 24 hours. The variance applied only to the Durango, Colorado, disposal cell, which was completed in 1990. A combination of good scheduling and favorable weather allowed the UMTRA Project to complete additional sites since 1990 without violating the temperature and rainfall limits.
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