Non-tectonic surface deformation

DOE-STD-1022-94

5.4.4.2 Non-tectonic surface deformation

Non-tectonic phenomena that can result in surface deformation at a facility site include glacially-induced

faulting, growth faulting, collapse due to underground voids such as found in Karst terrain, and subsidence

due to extensive fluid withdrawal.

Glacially-induced faults generally do not represent a significant displacement hazard because the conditions

that created them are no longer present. If residual stresses from Pleistocene glaciation are still present, these

features should be investigated with respect to their relationship to current in-situ stresses.

The existence of cavities in some geological materials (e.g. limestone, gypsum, anhydrite, etc.,) may lead to

ground collapse. If collapse features are present, they shall be considered and investigated with respect to

their potential for causing deformation of the facility site and, if so, whether engineered stabilization

measures are feasible.

Large, naturally occurring growth faults, as found in the coastal plain of Texas and Louisiana, can pose a

surface displacement hazard even though offset most likely occurs at a slower rate than that of tectonic

faults, they shall be identified and avoided in siting, and their displacements shall also be monitored. Some

growth faults and antithetic faults related to growth faults are not easily identified; therefore, investigations

of the potential amount and character of displacement shall be undertaken in regions where growth faults are

known to be present.

5.5 GEOTECHNICAL STUDIES

Geotechnical studies may include investigations for: (1) defining site soil properties as may be required for

hazard evaluations, and engineering analyses and designs; (2) assessing local soil site effects on ground

motions; (3) carrying out soil-structure interaction analyses; and (4) assessing potential of soil failure or

deformation induced by ground shaking (liquefaction, differential compaction, land sliding, etc.).

The extent of investigation to determine the geotechnical characteristics of a site depends on the performance

categories of the facilities, the subsurface conditions, and the extent of available information. For facilities

with SSCs in Performance Category 4, the geotechnical studies shall include, at a minimum, the

investigations specified in Sections 5.5.1 through 5.5.4 (see USNRC R. G. 1.132). Reduced scope of

investigation is allowed for sites containing facilities with SSCs in Performance Category 3 or lower, if the

additional uncertainties resulting from the less extensive investigation are acceptable and justified based on

analyses by the project team. By working with experienced geotechnical engineers and geologists, an

appropriate scope of investigations can be developed for a particular facility.

5.5.1 Site Investigations

Site investigations shall be conducted for facilities if the site information is not available or insufficient for

NPH assessment and design/evaluation of the particular facilities. Soil/rock profiles (cross-sections) at the

locations of the facilities shall be provided based on the results of site investigations. The quantification of

site soil/rock properties, such as classifications, strengths, compressibilities, densities, and wave velocities,

is needed for engineering design, and evaluations of soil amplification, soil-structure interaction, potential

for liquefaction, differential compaction, and land sliding. The properties required are intimately linked to

the designs and evaluations to be conducted. For example, for analyses of soil response effects or