Basic
Requirements for a
Geotechnical Investigation
When
a Geotechnical Investigation is Required
If the project
is expected to have significant cuts and/or fills, involves
unstable ground (e.g., landslides, rockfall areas), crosses,
wetlands or otherwise soft ground, or contains structures such
as bridges, retaining walls, large hydraulic/drainage
structures, a geotechnical investigation and design will
likely be needed.
If the project
contains any of the above elements the Geotechnical Division
should be involved early in the project development to provide
input.
Initiating
and Planning for a Geotechnical Investigation
The Regional
Materials Laboratory acts as a clearing-house for new
geotechnical work and are the first point of contact to
initiate geotechnical investigations and designs.
If its determined that the Geotechnical Services
Division will be doing the work, the Geotechnical Services
Division should be contacted to obtain a project specific
scope of work, and cost estimate to complete the required geotechnical investigation and
design. The
exception to this is bridge foundation design, in which case
the Office of Bridge and Structures is the first point of
contacts.
For those
wishing to obtain geotechnical services for their project, it
is important that they start as early as possible in the
project development process to prevent potential delays to the
project schedule. It
is difficult to provide an estimate of how long it typically
takes to complete a geotechnical design, as the time required
is very project specific. Depending on factors such as
Federal, State, and Local permits,
right of entry needs, overall complexity of the
project, the timely availability of the necessary site data
from the region project office, and overall workload of the
Geotechnical Services Division the time could ranges from 2 to
6 months.
Section
510 of the WSDOT State Design Manual provides detailed
guidance on what is required to initiate a geotechnical
investigation and design.
Special guidance regarding retaining walls is provided
in Section
1130 of the State Design Manual.
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