through a clear understanding of the hydrogeologic
logs may also be supplemented by geophysical methods.
environment in which the wastes are to be placed.
Geophysical surveys give the designer the advantage of
Hydrogeologic considerations to be addressed include:
examining large areas at one time, facilitating the
Review of published and unpublished data on
correlation of borehole data around the site and
ground-water availability and quality
delineation of overall site geology.
However, it is
Ground-water flow quantity and direction under
important to note that the usefulness of a given
the site *
geophysical method is dependent on site-specific
Relationship of the site to ground-water basin
conditions and must be assessed on a case-by-case
basis. Geophysical methods include:
Ground-water use near the site, including review
(1) Electrical "E" Logs-This process involves
measuring electrical properties of soils and geologic
(available from some state agencies)
formations in uncased boreholes. The data collected will
Identification of uppermost aquifers
yield information on potential of strata to transmit water,
Location of regional aquifers and aquicludes and
occurrence of water and general water quality. Cost may
regional flow information
vary depending on hole depth and condition.
b. Protection of surface-water resources is another
important concern in the design and operation of a
employs vertical electrical soundings (VES) which
hazardous waste land disposal/land treatment facility. A
transmit electrical currents into the ground. The VES
surface-water assessment of the site is recommended to
may be considered an electrical "drill hole" which may
determine (1) water quality of streams and other surface-
define subsurface strata. This relatively inexpensive
water sources within the area, and (2) the ratio of
technique enables rapid evaluation of subsurface
baseflow discharge from upstream sources to any
conditions to a depth of approximately 200 feet.
potential permitted discharges (to determine how much
(3) Magnetometer Survey-This method measures
magnetic intensity of rock and strata for defining geologic
c. Information relating to regional and site
structure. Magnetometer surveys can cover large areas
hydrogeologic conditions on the following is also
at minimum cost.
Geologic mapping of the site.
surveys use sonic waves created by small explosions (or
Detailed boring logs and test pits of subsurface
sledge hammer or other vibro-mechanical means) to
soils and geology characterizing the base of the
map variations in bedrock hardness. These surveys can
provide information on competency of bedrock (indicative
Detailed chemical analysis of all aquifers that are
of rock rippability) and degree of weathering, as well as
potential water supply sources or which have the
changes in these properties with depth. Seismic surveys
are capable of scanning large areas for a moderate cost.
g. Additional information on regional seismicity is
Soil classification and geotechnical properties.
required in seismically active areas of the United States:
Measurement of permeability of soils and
40 CFR 264.18 requires special seismic studies for new
formations between the base of the disposal
hazardous waste facilities in a number of western and
unit and uppermost aquifer.
midwestern states. Appendix VI to part 264 lists political
d. A comprehensive geotechnical testing program
jurisdiction for which this requirement is mandated. The
design engineer is also advised to review seismic zone
Soil classification tests.
maps presented in TM 5-809-10 (para 3-4) for additional
information. In seismically active areas, the services of a
Unconfined compressive strength tests.
soils engineer familiar with seismic engineering may be
Triaxial compression tests.
needed to determine the effects of seismic loads to
Direct shear tests.
shaking. Static and dynamic analysis may be required to
Background contaminant level tests (EM 11102-
predict potential slope failure.
h. In summary, data evaluation is critical to
These tests are typically conducted in accordance with
individual facility siting and must consider maximum
American Society for Testing and Materials (ASTM)
advantage of the site's hydrogeologic and geotechnical
factors. Assessment of soil engineering properties will
e. Methods of approach for site investigations may
dictate types of design and availability of on-site mate
be found in Design of Small Dams, US Department of
Interior (1973), TM 5-818-1, NAVFAC DM 7.1 and EPA
f. Subsurface information obtained from boring