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1 <br />753191 <br />ATTACHMENT A 341681 <br />LAND ANNOTATION <br />DURANGO, COLORADO PROCESSING SITE <br />NORTHERN, MIDDLE AND SOUTHERN PARCELS <br />The Uranium Mill Tailings Radiation Control Act (Public Law 95 -604), Section 104, requires <br />that the State notify any person who acquires a designated processing site of the nature and <br />extent of residual radioactive materials removed from the site, including notice of the date when <br />such action took place, and the condition of the site after such action. The following information <br />is provided to fulfill this requirement. <br />The Durango, Colorado processing site originally consisted of three separate land parcels. The <br />northern parcel contained the mill site, two tailings piles and remnants of old buildings. The, <br />southern parcel, located approximately 0.5 miles to the south, contained raffinate ponds, which <br />were used for the disposal and evaporation of contaminated liquids from the mill process. The <br />two sites are connected by a currently impassable service road cut into the face of Smelter <br />Mountain which is the third parcel. <br />Approximately 2,500,000 cubic yards of contaminated materials which included 1) tailings; 2) <br />subpile soils; 3).surfi.cial materials in the mill yard; 4) windblown materials; and 5) raffinate <br />ponds and contents were removed from the sites from 1 987 to 1990. The remediation was <br />conducted in accordance with regulations promulgated by the United States Environmental <br />Protection Agency (EPA), in 40 CFR 192. These regulations require that the concentration of <br />radium -226 in land averaged over any area of 100 square meters shall not exceed the background <br />level by more than: 5 pCi/g (picocuries per gram), averaged over the first 15 cm (centimeters) of <br />soil below the surface, and 15 pCi/g averaged over 15 cm thick layers of soil more than 15 cm <br />below the surface. <br />After remediation was complete the sites were backfilled with approximately 230,000 cubic <br />yards of clean material, graded for drainage and revegetated. Backfill materials were routinely <br />analyzed for radium -226 and were determined to have concentrations near background. Material <br />with radium -226 concentrations less than 5 pCi/g were used for surface backfill. Excavation of <br />residual radioactive material was also conducted for Thorium -230 on the southern parcel. For <br />thorium -230, the cleanup standard was determined as a projected 1,000 year Radium -226 <br />concentration based on the eventual decay of the thorium to radium. This resulted in a thorium- <br />230 concentration of approximately 35 pCi/g as the clean-up standard. All verification soil <br />samples from the two sites met the EPA standards of 5 and 15 pCi/g radium 226 plus background <br />(1.6 pCi/g) except for grid H -38 -20 which, including the thorium -230 results, after 1000 years <br />would have a projected concentration of 18.6 pCi/g of radium -226. (The actual concentrations at <br />this location are 49.4 pCi/g thorium -230 and 1.8 pCi/g radium -226). This grid is located on the <br />southern parcel, as shown on the attached map. This grid is covered with 2.5 to 5 feet of clean <br />backfill. <br />.EXH.IBIT -C . <br />