What does a consulting geologist do?
Well, a few different things...
Geologic Hazards Assessment
Geologic hazards include landslides, earthquakes, fault movement, ground settlement, cracking and sliding related to earthquake shaking, volcanic eruptions and related hazards, erosion, sedimentation, and floods. All these hazards can potentially affect property and human lives. Many cities and counties now require some form of geologic hazards assessment for development, so these hazards may be avoided or remedied as part of the project design.
Critical facilities, such as hospitals or fire stations, must continue to function during natural disasters and are required to have a very careful geologic hazards evaluation. Hazard evaluations are also typically performed for other structures, such as schools, where the consequences of failure are very high.
Nolan Associates provides geologic hazards assessments for individual projects ranging from single-family residences to hospitals and dams. We also prepare area-wide geologic hazard evaluations for city and county general plans (seismic safety and geotechnical hazards components) and land management plans for conservation of open space. These studies are used to guide long-term planning decisions.
Landslide Evaluation and Repair
Once a landslide has taken place, it may come to rest in a
stable configuration, or it may be capable of further movement. To repair
things damaged by landsliding or to use property underlain by a landslide,
it is necessary to determine whether the landslide is stable, and, if not,
what means can be employed to make it stable. A landslide must be
characterized in terms of width, length, depth, types of geologic materials
involved, groundwater levels, and causative factors. This information provides
a basis for design of stabilization measures. Nolan Associates
provides landslide remediation services for private
clients and public agencies.
Paleo (meaning old or ancient) Seismology (the study of
earthquakes) is the study of prehistoric earthquakes by examining the records
they have left in sedimentary layers. Earthquakes
are produced by movement on faults-- cracks in the earth's crust--caused by
the buildup of stress in the crust. When a fault slips, the release of stored
energy results in waves traveling through the earth, which we
experience as an earthquake. The fault movement offsets layers at the earth's
surface. The most common method for studying prehistoric earthquakes is to
excavate trenches across faults so that we can examine the way in which
layers of different ages were offset by fault movement.
The variation in offset of layers of different ages can be used to find when earthquakes have
occurred in the past, how frequently they occur, and approximately how large
they were. This type of work is done to aid public and private organizations
in earthquake hazard assessment and earthquake preparedness planning. Most of
this type of work is funded by research grants from the U.S. Geological
Hydrogeology is the study of the occurrence and movement of
groundwater. The most common application of hydrogeology
presently is in the study and treatment of groundwater contamination. Leaky
underground fuel tanks, accidental spills of industrial solvents,
concentrated discharge of sewage effluent, and other activities of man have
the potential to contaminate groundwater that is used for drinking and
agriculture. Hydrogeology is also used in water resource evaluation and
management. In California, the growing population is placing increasing demands
on surface and groundwater supplies. Nolan Associates participates in the
evaluation of water use impacts on ground water availability and groundwater
Engineering geology is application of geologic principals
to engineering practice, to help insure that geologic factors
are adequately accounted for in design, construction, operation, and maintenance of
engineered structures. Engineering geology practice includes an understanding of
the character and properties of geologic materials and processes as they relate to the construction of
earthworks and foundations. It includes the recognition of geologic hazards
as well as an appreciation of the role of groundwater, rock structure, and
soil properties in engineering design.
Geologic Impacts Assessment
In California, the assessment of
potential environmental impacts and the means for mitigating those impacts
is required by the California Environmental Quality
Act (CEQA) for many types of new development. Nolan Associates
provides geologic impacts assessments as part of the CEQA certification
process, generally as a subcontractor to an Environmental Impact Report