Location of rock exposure(s) on a topographic map, particularly with respect to
the site being investigated, including strike and dip measurements for
sedimentary rock strata, and orientation, bearing and plunge measurements for
predominant metamorphic/igneous linear features (large and small scale).
Photograph(s) of exposure(s).
Measured section, with name(s) of stratigraphic units present. A measured
section includes a bed by bed description of the exposure using appropriate
lithologic terminology. A scale drawing or photograph of the section,
including sample locations, should be part of the outcrop description.
Structural features such as folds, faults, joints, fractures, cleavage, schistosity,
and lineation. Other features that can control the hydraulic properties of the
units such as solution cavities also should be noted. It is important to
determine the orientation of these features, as they may exert significant
influence on the local or regional movement of ground water. When
sedimentary strata are nearly horizontal and structurally uncomplicated, the
orientation of any joints not parallel to bedding should be determined, as
movement of ground water along joints and bedding planes can be a significant
part of the ground water flow regime.
Where fractures, faults, or subsurface conduits exist, maps of fracture traces, fault
traces, and subsurface conduits should be included as part of, or in addition to, the geologic
map prepared for the site. Mapping of subsurface conduits is successfully accomplished by
performing tracer studies. Fracture trace mapping is performed by analyzing aerial
photographs, and is often supplemented with information from field reconnaissance, tracer
tests, and/or geophysical investigations.
Soil maps are typically available from the U.S. Department of Agriculture's Soil
Conservation Service. A soil map should be prepared for facilities that do not have one
available, or for facilities where existing soil maps are incomplete or out of date (e.g., soils
have been disturbed). A soil survey will involve mapping soils with respect to their unit and
type, based primarily on grain size distribution.
Cone Penetrometer Survey
Cone penetrometer testing (CPT) consists of advancing an electric, telescoping
penetrometer tip into a subsurface formation to determine the end bearing and side friction
components of penetration resistance (ASTM D3441 86). Application of the CPT method is
limited by the availability of equipment and by the relatively few contractors that offer
conventional or specialized CPT services. In all cases, lithologic data obtained from CPT