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EF RADINFO Logo National Emission Standards for Hazardous Air Pollutants:
Subpart W: Operating Uranium Mill Tailings Piles



Description of Source:Uranium ore generally contains less than 1% uranium. Thus, the process used to extract the uranium from the ore generates a large amount of waste. This waste is called uranium mill tailings. Tailings are collected in impoundments that vary in size from 20 to 400 acres. The radium contained within the mill tailings decays and emits Radon-222, a radioactive gas known to cause lung cancer in people. This Subpart applies to operating uranium mill tailings piles. Subpart T applies to the disposal of uranium mill tailings piles once they are no longer operational.


The Standard:Radon-222 emissions to the ambient air from an existing uranium mill tailings pile shall not exceed 20 picocuries per square meter per second of Radon-222. In addition, new tailings piles must meet one of the two following work practices:

  1. Phased disposal, using lined impoundments which are filled and then immediately dried and covered to meet federal standards. No more than two piles can be in operation at any time (including existing impoundments) and they cannot be more than 40 acres.
  2. Continuous disposal which requires that tailings be dewatered and immediately disposed of. No more than 10 acres can be uncovered at any time and the tailings pile must be operated in accordance with 40 CFR Part 192.32(a).


Reporting Requirements:Owners and operators of uranium mill tailings piles must conduct radon emissions testing each year and report the results to EPA in writing.


More Information:Follow this link to the 40 CFR 61, Subpart W.Exit Disclaimer
Follow this link to the Radiation NESHAPs Home Page.

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