1983-06-03_REVISION - M1977285 (2)

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43.90(d)(4) providing for stability of the impoundment system itself, overall • stability, erosion potential, and geomorphology of surrounding terrain shall be evaluated to assure that there are no ongoing or potential processes, such as gully erosion, which would lead to impoundment instability; CS) the impoundment shall not be located near a capable fault that could cause a maximum credible earthquake larger than that which the impoundment could reasonably be expected to withstand; and (6) the impoundment should be designed to incorporate features which will promote deposition. Design features which promote deposi- tion of sediment suspended in any runoff which flows into the impoundment area might be utilized. The object of such a design feature would be to enhance the thickness of cover over time. (e) Groundwater Protection. The following groundwater protection require- ments and those in 43.90(f) and (g) and Appendix 43-A apply during operations and until closure is completed. Groundwater monitoring to comply with these standards is required by 43.90(m). (1) The primary groundwater protection standard is a design standard for surface impoundments used to manage uranium and thorium byproduct material. Unless exempted under 43.90(e)(3), surface impoundments (except for an existing portion) shall have a liner that is designed, constructed, and installed to prevent any migration of wastes out of the impoundment to the adjacent • subsurface soil, groundwater, or surface water at any time during the active life (including the closure period) of the impoundment. If the liner is constructed of materials that may allow wastes to migrate into the liner during the active Life of the facility, impoundment closure shall include removal or decon- tamination of all waste residues, contaminated containment system components (liners, etc.), contaminated subsoils, and structures and equipment contaminated with waste and leachate. For impound- ments that will be closed with the liner material left in place, the liner shall be constructed of materials that can prevent wastes from migrating into the liner during the active life of the facility. (2) The liner required by (e)(1) above shall be: (i) constructed of materials that have appropriate chemical properties and sufficient strength and thickness to prevent failure due to pressure gradients (includic~g static head and external hydrogeologic forces), physical contact with the waste or leachate to which they are exposed, climatic conditions, the stress of installation, and the stress of daily operation; (ii) placed upon a foundation or base capable of providing support to the liner and resistance to pressure gradients above and below the liner to prevent failure of the Liner • due to settlement, compression, or uplift; and 43 - 17 (April 1990)