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7 <br /> 2. WASTE DUMP RADIONUCLIDE CONTAMiVRTION <br /> FIELD WORK AND LITERATURE SEARCH <br /> An estimate of the extent of radionuclide contamination In the waste dumps of <br /> 7 each of the nine inactive uranium mine complexes teas made from a survey of <br /> available literature and public mine production records for 1948-1970, and <br /> from consultation with a recognized authority on mine production (William L. <br /> Chenoweth, Grand Junction, Colorado) . The estimates were developed according <br /> to mining scenarios and geologic units. <br /> Field measurements were taken on the dumps of each mine to estimate the near- <br /> surface equivalent radium concentrations in picocuries per gran (pCi/g) . A <br /> delta-gamma scintillometer was used to perform these in situ measurements. A <br /> delta-gamma scintillometer measures gamma rays, but includes a removable <br /> shield that permits distinguishing background radiation from the radiation <br /> directly beneath the scintillometer, The calculation of results using this <br /> instrument includes subtraction of an average factor to account for naturally <br /> occurring thorium and potassium. The remaining gamaa-ray signal is assumed to <br /> come entirely from radium in the soil . The results are reported in units of <br /> equivalent pCi/g of radium because gamma-rays from radium danghters are <br /> measured. <br /> DISCUSSION OF RESULTS <br /> The results of the literature search of mine production records are contained <br /> in Appendix B. Ore production was estimated from Atomic Energy Commission <br /> (AEC) records, State of Utah records, and information in the personal files of <br /> William L. CLenoweth. Ore production is believed accurate to within a few <br /> hundred tons. <br /> Ore-to-waste ratios were obtained from various U.S. Bureau of Mines reports <br /> of uranium mining on the Colorado Plateau. These ratios may be conservative <br /> as the ore and waste were measured while mining was occurring in ore bodies <br /> 1 and do not take into account drifting in barren ground to reach other ore <br /> bodies. <br /> The results of the delta-gamma scintillometer measurements are listed in <br /> Table 4. The standards for the DOE Uranium Mill Tailings Remedial Action <br /> Program (Uh-MP) are 5 pCi/g above background in the top 15 c■ of soil . and <br /> 15 pCi/g above background for any deeper 15-cm-thick layer, averaged over <br /> 100 m2. Background concentrations are typically about I pCi/g. The radium <br /> concentration of the Grand Junction (Climax) , Colorado, mill tailings pile. * <br /> for example, is approximately 700 pCi/g. These values are provided for <br /> comparison purposes. <br /> Equivalent radium concentrations ranged from essentially background values at <br /> .� the Brushy Basin Mine and much of th. Rey Grecp tc - ,jg; ur a.,oi <br /> i <br /> 7 'Remedial Actions at the Forser Climax Uranium Company Uranium Mill Site <br /> Grand Junction, Mesa County, Colorado, Final Environmental Impact Statement, <br /> DOE/EIS-128-F, U.S. Department of Energy, December, 1986. <br /> 6 <br />