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002437 ATT ACHMENT A LAND ANNOTATION DURANGO, COLORADO PROCESSING SITE NORTHERN, MIDDLE AND SOUTHERN PARCELS The Uraniwn Mill Tailings Radiation Control Act (Public Law 95-604), Section 104, requires that the State notify any person who purchases a designated processing site of the nature and extent of residual radioactive materials removed from the site, including notice of the date when such action took place, and the condition of the site after such action. The following information is provided to fulfill this requirement. The Durango, Colorado processing site originally consisted of th.J:ee separate land parcels. The northern parcel contained the mill site, two tailings piles and remnants of old buildings. The southern parcel, located approximately 0.5 miles to the south, contained raffinate ponds, which were used for the disposal and evaporation of contaminated liquids from the mill process. The two sites are cOlUlected by a cw-rently impassable service road cut into the face of Smelter Mountain which is the third parcel. Approximately 2,500,000 cubic ya.:ds of contammated materials which included 1) tailings; 2) $ubpiJe soils; 3) surficial materials in the mill yard; 4) windblown materials; and 5) raffinate ponds and contents were removed from the sites from 1987 to 1990. The remediation was conducted in accordance with regulations promulgated by the U.S. Environmental Protection Agency, in 40 CFR 192. These regulations require that the concentration of radium-226 in land averaged over any area of 100 square meters shall not exceed the background level by more than: 5 pCilg (picocuries per gram), averaged over the fLTst 15 Cm of soil below the surface, and 15 pCi/g averaged over 15 cm thick layers below the surface. After remediation was complete the sites were backfilled with approximately 230,000 cubic yards of clean material, graded for drainage and revegetated. Backfill materials were routinely analyzed for radium-226 and were determined to have concentrations near background. Material with radiurn-226 concentrations less than 5 pCi/g wen: used for surface backfill. Excavation of residual radioactive material was also condueted for Thorium-230 on the southern parcel. For thorium-230, the cleanup standard was determined as a projected 1,000 year Radium-226 concentration based on the ingrowth of the thorium to radium This resulted in a thorium-230 concentration of approximately 35 pCi/g as the clean-up standard. AU verification soil samples from the two sites met the EP A standards of 5 and 15 pCilg radium 226 plus background (1.6 pCi/g) except for grid H-38-20 which, including the thorium-230 results, after 1000 years would have a projected concentration of 18.6 pCi/g of radiwn-226. (The actual concentrations at this location are 49.4 pCilg thorium-230 and 1.8 pCilg radiurn-226). This grid is located on the southern parcel, as shown on the attached map. The northern parcel also contains slag from a lead smelter which operated On the site prior to