| (1) installation of bottom liners. Where synthetic liners are used, a leakage-detection system must be installed immediately below the liner to ensure detection of any major failures. This is in addition to the groundwater monitoring program conducted as provided in subsection (cc) of this section. Where clay liners are proposed or relatively thin, in situ clay soils are to be relied upon for seepage control, tests must be conducted with representative tailings solutions and clay materials to confirm that no significant deterioration of permeability or stability properties will occur with continuous exposure of clay to by-product material solutions. Tests must be run for a sufficient period of time to reveal any effects that may occur; (2) mill process designs that provide the maximum practicable recycle of solutions and conservation of water to reduce the net input of liquid to the by-product material impoundment; (3) dewatering of by-product material solutions by process devices and/or in situ drainage systems. At new sites, by-product material solutions must be dewatered by a drainage system installed at the bottom of the impoundment to lower the phreatic surface and reduce the driving head of seepage, unless tests show by-product material solutions are not amenable to such a system. Where in situ dewatering is to be conducted, the impoundment bottom must be graded to assure that the drains are at a low point. The drains must be protected by suitable filter materials to assure that drains remain free-running. The drainage system must also be adequately sized to assure good drainage; and (4) neutralization to promote immobilization of hazardous constituents. (m) Technical specifications must be prepared for installation of seepage control systems. A quality assurance, testing, and inspection program, which includes supervision by a qualified engineer or scientist, must be established to assure that specifications are met. If adverse groundwater impacts or conditions conducive to adverse groundwater impacts occur due to seepage, action must be taken to alleviate the impacts or conditions and restore groundwater quality to levels consistent with those before operations began. The specific seepage control and groundwater protection method, or combination of methods, to be used must be worked out on a site-specific basis. (n) In support of a by-product material disposal system proposal, the applicant/licensee must supply the following information: (1) the chemical and radioactive characteristics of the waste solutions; (2) the characteristics of the underlying soil and geologic formations particularly as they will control transport of contaminants and solutions. This must include detailed information concerning extent, thickness, uniformity, shape, and orientation of underlying strata. Hydraulic gradients and conductivities of the various formations must be determined. This information must be gathered by borings and field survey methods taken within the proposed impoundment area and in surrounding areas where contaminants might migrate to groundwater. The information gathered on boreholes must include both geologic and geophysical logs in sufficient number and degree of sophistication to allow determining significant discontinuities, fractures, and channeled deposits of high hydraulic conductivity. If field survey methods are used, they should be in addition to and calibrated with borehole logging. Hydrologic parameters such as permeability must not be determined on the basis of laboratory analysis of samples alone. A sufficient amount of field testing (e.g., pump tests) must be conducted to assure actual field properties are adequately understood. Testing must be conducted to make possible estimates of chemisorption attenuation properties of underlying soil and rock; and (3) location, extent, quality, capacity, and current uses of any groundwater at and near the site. (o) If ore is stockpiled, methods must be used to minimize penetration of radionuclides and other substances into underlying soils. (p) In disposing of by-product material, licensees must place an earthen cover over the by-product material at the end of the facility's operations and shall close the waste disposal area in accordance with a design that provides reasonable assurance of control of radiological hazards to the following: (1) be effective for 1,000 years to the extent reasonably achievable and, in any case, for at least 200 years; and (2) limit releases of radon-222 from uranium by-product materials and radon-220 from thorium by-product materials to the atmosphere so as not to exceed an average release rate of 20 picocuries per square meter per second (pCi/m2 s) to the extent practicable throughout the effective design life determined in accordance with paragraph (1) of this subsection. This average applies to the entire surface of each disposal area over a period of at least one year, but a short period compared to 100 years. Radon will come from both by-product materials and cover materials. Radon emissions from cover materials should be estimated as part of developing a closure plan for each site. The standard, however, applies only to emissions from by-product materials to the atmosphere. (q) In computing required by-product material cover thicknesses, moisture in soils in excess of amounts found normally in similar soils in similar circumstances may not be considered. Direct gamma exposure from the by-product material should be reduced to background levels. The effects of any thin synthetic layer may not be taken into account in determining the calculated radon exhalation level. Cover may not include materials that contain elevated levels of radium. Soils used for near-surface cover must be essentially the same, as far as radioactivity is concerned, as that of surrounding surface soils. If non-soil materials are proposed as cover materials, the licensee must demonstrate that such materials will not crack or degrade by differential settlement, weathering, or other mechanisms over the long term. (r) As soon as reasonably achievable after emplacement of the final cover to limit releases of radon-222 from uranium by-product material and prior to placement of erosion protection barriers of other features necessary for long-term control of the tailings, the licensee must verify through appropriate testing and analysis that the design and construction of the final radon barrier is effective in limiting releases of radon-222 to a level not exceeding 20pCi/m2 s averaged over the entire pile or impoundment using the procedures described in Appendix B, method 115 of 40 CFR Part 61, or another method of verification approved by the agency as being at least as effective in demonstrating the effectiveness of the final radon barrier. (s) When phased emplacement of the final radon barrier is included in the applicable reclamation plan, as defined in §336.1105(25) of this title, the verification of radon-222 release rates required in subsection (dd) of this section must be conducted for each portion of the pile or impoundment as the final radon barrier for that portion is emplaced. (t) Within 90 days of the completion of all testing and analysis relevant to the required verification in subsection (dd)(3) and (dd)(4) of this section, the uranium recovery licensee must report to the agency the results detailing the actions taken to verify that levels of release of radon-222 do not exceed 20 pCi/m2 s when averaged over the entire pile or impoundment. The licensee must maintain records documenting the source of input parameters, including the results of all measurements on which they are based, the calculations and/or analytical methods used to derive values for input parameters, and the procedure used to determine compliance. These records must be maintained until termination of the license and shall be kept in a form suitable for transfer to the custodial agency at the time of transfer of the site to the state or federal government in accordance with §336.1131 of this title (relating to Land Ownership of By-Product Material Disposal Sites). (u) Near-surface cover materials may not include waste, rock, or other materials that contain elevated levels of radium. Soils used for near-surface cover must be essentially the same, as far as radioactivity is concerned, as surrounding surface soils. This is to ensure that surface radon exhalation is not significantly above background because of the cover material itself. (v) The design requirements for longevity and control of radon releases apply to any portion of a licensed and/or disposal site unless such portion contains a concentration of radium in land averaged over areas of 100 square meters (m2 ), that, as a result of by-product material, does not exceed the background level by more than: (1) 5 picocuries per gram (pCi/g) of radium-226, or in the case of thorium by-product material, radium-228, averaged over the first 15 centimeters (cm) below the surface; and Cont'd... |
