§ 960.4-2-1 Geohydrology. ( a ) *Qualifying condition.* The present and expected geohydrologic setting of a site shall be compatible with waste containment and isolation. The geohydrologic setting, considering the characteristics of and the processes operating within the geologic setting, shall permit compliance with ( 1 ) the requirements specified in § 960.4-1 for radionuclide releases to the accessible environment and
( 2 ) the requirements specified in 10 CFR 60.113 for radionuclide releases from the engineered-barrier system using reasonably available technology.
( b ) *Favorable conditions.* ( 1 ) Site conditions such that the pre-waste-emplacement ground-water travel time along any path of likely radionuclide travel from the disturbed zone to the accessible environment would be more than 10,000 years.
( 2 ) The nature and rates of hydrologic processes operating within the geologic setting during the Quaternary Period would, if continued into the future, not affect or would favorably affect the ability of the geologic repository to isolate the waste during the next 100,000 years.
( 3 ) Sites that have stratigraphic, structural, and hydrologic features such that the geohydrologic system can be readily characterized and modeled with reasonable certainty.
( 4 ) For disposal in the saturated zone, at least one of the following pre-waste-emplacement conditions exists: ( i ) A host rock and immediately surrounding geohydrologic units with low hydraulic conductivities.
( ii ) A downward or predominantly horizontal hydraulic gradient in the host rock and in the immediately surrounding geohydrologic units.
( iii ) A low hydraulic gradient in and between the host rock and the immediately surrounding geohydrologic units.
( iv ) High effective porosity together with low hydraulic conductivity in rock units along paths of likely radionuclide travel between the host rock and the accessible environment.
( 5 ) For disposal in the unsaturated zone, at least one of the following pre-waste-emplacement conditions exists: ( i ) A low and nearly constant degree of saturation in the host rock and in the immediately surrounding geohydrologic units.
( ii ) A water table sufficiently below the underground facility such that the fully saturated voids continuous with the water table do not encounter the host rock.
( iii ) A geohydrologic unit above the host rock that would divert the downward infiltration of water beyond the limits of the emplaced waste.
( iv ) A host rock that provides for free drainage.
( v ) A climatic regime in which the average annual historical precipitation is a small fraction of the average annual potential evapotranspiration. Note:
The DOE will, in accordance with the general principles set forth in § 960.1 of these regulations, revise the guidelines as necessary, to ensure consistency with the final NRC regulations on the unsaturated zone, which were published as a proposed rule on February 16, 1984, in 49 FR 5934.
( c ) *Potentially adverse conditions.* ( 1 ) Expected changes in geohydrologic conditions—such as changes in the hydraulic gradient, the hydraulic conductivity, the effective porosity, and the ground-water flux through the host rock and the surrounding geohydrologic units—sufficient to significantly increase the transport of radionuclides to the accessible environment as compared with pre-waste-emplacement conditions.
( 2 ) The presence of ground-water sources, suitable for crop irrigation or human consumption without treatment, along ground-water flow paths from the host rock to the accessible environment.
( 3 ) The presence in the geologic setting of stratigraphic or structural features—such as dikes, sills, faults, shear zones, folds, dissolution effects, or brine pockets—if their presence could significantly contribute to the difficulty of characterizing or modeling the geohydrologic system.
( d ) *Disqualifying condition.* A site shall be disqualified if the pre-waste-emplacement ground-water travel time from the disturbed zone to the accessible environment is expected to be less than 1,000 years along any pathway of likely and significant radionuclide travel.