TM 5-818-5/AFM 88-5, Chap 6/NAVFAC P-418
CHAPTER 3
GEOLOGIC, SOIL, AND GROUNDWATER INVESTIGATIONS
3-1. General. Before selecting or designing a sys-
3-2. Geologic and soil conditions. An un-
tem for dewatering an excavation, it is necessary to
derstanding of the geology of the area is necessary to
consider or investigate subsurface soils, groundwater
plan any investigation of subsurface soil conditions.
conditions, power availability, and other factors as
Information obtained from the geologic and soil in-
listed in table 3-1. The extent and detail of these in-
vestigations as outlined in TM 5-818-1/AFM 88-3,
vestigations will depend on the effect groundwater
Chapter 7 or NAVFAC DM7.1, should be used in
and hydrostatic pressure will have on the construction
evaluating a dewatering or groundwater control prob-
of the project and the complexity of the dewatering
lem. Depending on the completeness of information
problem.
available, it may be possible to postulate the general
Table 3-1. Preliminary Investigations
Reference
Investigate
Item
Para 3-2; TM 5-818-1/
Geologic and soil Type, stratification, and
AFM 88-3, Chapter 7
thickness of soil involved
conditions
NAVFAC DM7.1
in excavation and
dewatering
Reliability of power system,
Criticality
damage to excavation or
foundation in event of
f a i l u r e , rate of rebound,
etc.
Para 2-3 and 3-3
Groundwater table or hydro-
Groundwater or
piezometric
static pressure in area and
its source. Variation with
pressure
river stage, season of year,
characteristics
e t c . Type of seepage (arte-
s i a n , gravity, combined).
C h e m i c a l characteristics
and temperature of
groundwater .
Determine permeability from
Para 3-4; Appendix C
Permeability
visual, field, or labora-
t o r y tests, preferably by
field tests.
Para 3-5
Power
Availability, reliability,
and capacity of power at
site.
Para 3-6
D e g r e e of possible Rainfall in area. Runoff
High-
characteristics.
water levels in nearby
bodies of water.
3-1
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