1. (1) The applicant must use site-specific geologic information in designing and assessing requirements for the underground mined repository.
2. (2) Documents containing detailed design and construction information must be submitted in the permit application. In addition to the documents required pursuant to Subpart 383-3 of this Part, these documents must include all relevant site-specific data and descriptions regarding the characteristics of the geologic unit or units around the excavation; proposed support and rock stabilization methods; design calculations of critical support elements; seismic analyses, and a map or maps of the underground mined repository at a scale of not less than one inch to 100 feet.
3. (3) The underground mined repository must be designed and constructed so that any surficial subsidence resulting from the mine will not create a significant depression that could result in surface waters' ponding and draining into the groundwater system in which the underground mined repository is constructed.

4. (4) The underground mined repository must be designed so that areas under construction are isolated from radioactive waste already in place.

   (b) Structural stability requirements.

5. (1) Structural stability analyses must be performed by a licensed engineer utilizing site-specific engineering properties.
6. (2) The underground mined repository and associated facilities must be designed to remain structurally stable after the occurrence of any single design-basis major phenomena.

7. (3) The excavation techniques used in construction must be designed and implemented to minimize:

   1. (i) the potential for increasing the flow of groundwater through the surrounding rock; and
   2. (ii) the potential for creating a pathway for groundwater or radionuclide movement.
8. (4) The proposed excavation and underground support systems must be based on site-specific engineering properties of the geologic unit. A minimum factor of safety of two must be used in the design for calculated load conditions under normal operating conditions.

9. (5) The design and construction of the facility must be sufficiently flexible to allow for necessary modifications in design and/or construction if conditions are encountered in the geologic unit that are significantly different from those used in the design of underground supports and in the stability analyses. If such conditions are encountered, the design and/or construction must be modified by a licensed engineer as necessary to comply with the requirements of this Part and must be approved by the department as a modification of the permit. Design calculations and analyses for any changed conditions must be submitted to the department in the application for permit modification. Construction inspection and documentation must be performed to verify that these changes have been incorporated into the construction.

   (c) Water infiltration.

10. (1) The underground mined repository must be designed and constructed to minimize and control water infiltration into the underground mined repository during the operation period and, as necessary to safely perform facility closure, during the closure period. During facility closure, the underground mined repository will be sealed. After it has been sealed, the underground mined repository will be allowed to revert to the natural hydrologic conditions.
11. (2) The underground mined repository geometry and disposal units must be designed and constructed to direct water that enters the repository during the operation period away from the radioactive waste already in place.
12. (3) The disposal units must be designed and constructed with an internal drainage system to minimize the contact of infiltrating water with the waste during the operation period. The drainage system must include collection points so that any water infiltrating the disposal units during the operation period and, as necessary, during facility closure can be monitored, tested, and treated as necessary, before release.
13. (4) The disposal units must be designed and constructed to minimize the flow of groundwater through the disposal unit once the underground mined repository has been sealed and allowed to revert to the natural hydrogeologic conditions.

14. (5) Hydrogeologic data used to assess water infiltration characteristics and establish related design and construction requirements for the underground mined repository must be gathered at the elevation at which the underground mined repository is to be constructed.

    (d) Bulkheads, seals, and other engineered barriers.

    Bulkheads are engineered structural barriers or partitions dividing the underground mined repository into waste disposal compartments and work areas. Seals are engineered features that employ techniques such as water stops, rock keyways, grouts, coatings, adhesive agents, or fluids to achieve airtight and/or watertight closure of the underground mined repository and waste disposal units. Other engineered barriers are designed features of the underground mined repository that serve to isolate or prevent water seepage and/or radionuclide migration from one area or disposal unit to another area of disposal unit; or from the underground mined repository to the surface environment.

15. (1) The underground mined repository design must incorporate bulkheads, seals, and other engineered barriers to prevent the premature infiltration of water into open areas, the escape of radioactive or hazardous gases, and the intrusion of personnel into filled disposal units from the open areas.
16. (2) Those bulkheads, seals, and other engineered barriers whose performance is critical to ensure that the underground mined repository facility will meet the performance objectives must be designed based on site-specific analyses.
17. (3) Bulkheads must be designed to isolate filled and closed units from active work areas and prevent the release of radionuclides from the closed units.

18. (4) Seals must be designed to deter radionuclide migration from the mined repository and disposal units.

    1. (i) Seals for shafts and boreholes connecting the underground mined repository area with the ground surface must be designed to maintain their integrity and not serve as pathways for radionuclide migration away from the repository for a period sufficient to meet the performance objectives.
    2. (ii) Seals for shafts and boreholes must be designed and located so they do not become infiltration pathways that could adversely affect the ability of the underground mined repository to meet the performance objectives.

19. (5) Materials and placement methods for bulkheads, seals, and other engineered barriers must be selected to minimize:

    1. (i) the potential for creating a pathway for groundwater to contact the waste; and

    2. (ii) for radionuclide migration through existing pathways.

       (e) Ventilation.

       Air exiting the ventilation system of the underground mined repository must be monitored and treated, as necessary, to meet the requirements of section 382.11 of this Title.

(a) General requirements.