CH2MHill, Tailings Outfall, Juneau, Alaska, USA:
A deep-water tailing outfall was
proposed to run offshore from Juneau to Stevens Passage in water
depths ranging from 1 to 200 m. A detailed marine geophysical
survey was conducted by Golder to select the best route for the
outfall, to map the regional deep stratigraphy, and to select
locations for piston cores for sediment sampling. The survey was
conducted with dual frequency digital echosounder, side scan
sonar, subbottom profiler (SBP), seismic reflection system and
DGPS navigation. The survey covered over 200 km of trackline and
achieved subsurface penetration of up to 20 m with the SBP and
300 m with the seismic reflection system.
US Army Crops of Engineers, Navigation, Cook Inlet, Alaska, USA:
A feasibility study
for the development of a navigational channel between Cook Inlet
and Iliamna Lake using marine seismic reflection.
Parsons Brinckerhoff, Boston Harbor Outfall Tunnel, Maryland, USA:
A marine outfall tunnel, 8 m in diameter, and 16 km long, was
to be bored 100 m below the harbor floor. A two phase geophysical
program had the following objectives: develop a detailed
bathymetric map of the seafloor along the proposed corridor;
determine the thickness of unconsolidated marine sediment
overlying bedrock; map the top of bedrock; identify and map major
bedrock fault zones and intrusive bodies; and identify bedrock
conditions that might have an adverse effect on tunneling. The
objectives were achieved using a combination of precision digital
bathymetry, subbottom profiling, single and multi channel
reflection and seismic refraction.
TransMountain Pipeline Company, TransMountain Pipeline Project, Puget Sound, Washinton, USA:
Golder Associates was contracted to provide all geologic and
geotechnical work in support of permitting and preliminary design
for a 220 km long, 1 m diameter oil pipeline. The geophysical and
geotechnical work involved site characterization along the
terrestrial route, marine crossings, shore approaches, river
crossings, and onshore facilities. Over 500 km of marine survey
transects were run to obtain precision bathymetric, side scan
sonar, subbottom , and seismic reflection data. Borings and
sediment samples were used to confirm the interpretation of the
shallow geophysical data. Subsurface penetration of over 100 m
was typical for most of the route in water depths from 5 to 200
m.
US ACOE/Argonne National Labs, Aberdeen Proving Ground, Cheasapeake Bay, Maryland, USA:
Golder Associates conducted a comprehensive marine geophysical
investigation in the Chesapeake Bay Estuary, and interconnecting
waterways and rivers adjacent to the Aberdeen Proving Ground. The
purpose of the investigation was to clarify the local
hydrogeologic framework, map buried offshore channels, and
determine the depth to bedrock. Over 150 km of geophysical data
were gathered using sidescan sonar, high-resolution seismic
reflection systems, magnetometry, precision bathymetry, and dGPS
navigation. The survey identified both shallow (5 to 10 m) and
deep (30 to 50 m) paleochannels, located and mapped surficial
ferrous and and nonferrous debris, and mapped the top of bedrock
at 200 m below the sea floor.
SAIMIC/Bechtel Chile, S.A., Valparaiso Outfall/Los Pelambres Terminal, Valparaiso, Chile:
A marine outfall is to be constructed for the city of
Valparaiso that will extend 600 m offshore from the land tunnel
portion of the sewerage system. To assist in selecting the
pipeline route, and design of the support structures for the
pipeline, SAIMIC contracted Golder Associates to conduct a
detailed marine geophysical survey. Over 15 km of bathymetric,
subbottom and seismic reflection data were obtained during the
investigation. A map showing the thickness of unconsolidated
sediment, and depth to top of bedrock was developed in the
project area. Maximum depth to bedrock was 40 meters.
In Los Vilos, Chile a comprehensive marine geophysical survey was
conducted to assist in the design of a new marine terminal for
loading ore carriers. Golder was contracted by Bechtel to obtain
depth to top of bedrock in the area of the proposed terminal. The
pier and terminal facility will extend approximately 600 m
offshore in water depths of 20 m. The bedrock depth varied from 0
to 60 m below the seafloor.
PTI, Ward Cove Environmental Survey, Ketchikan, Alaska, USA:
A marine geophysical survey was conducted as part of the
sediment remediation project for Ward Cove, a small embayment
used for log storage and effluent discharge from a former pulp
mill. The primary objective of the geophysical survey was to
provide detailed characterization of the physical features of
Ward Cove and to assist in locating coring stations for obtaining
sediment samples. The survey included multibeam precision
echosounding, side scanning sonar, subbottom profiling, marine
magnetometry, seismic reflection profiling, and dGPS navigation.
Over 50 km of geophysical data transects were acquired with a
maximum subsurface penetration of 70 m.
United States Coast Guard, Summerland Oilfield Survey, Summerland, California, USA:
Golder Associates was contracted by the Unites States Coast
Guard to conduct a comprehensive nearshore marine geophysical
survey off Summerland, California. The purpose of the
investigation was to locate and map surface and subsurface debris
associated with oil production activities that occurred in this
area in the early 1900's. Wells, piers and other structures had
been abandoned and for the most part were buried although there
was expected to be a considerable amount of timber, cables,
chain, etc. on the seafloor. The marine geophysical survey used
differential GPS in conjunction with a precision digital
echosounder, side scan sonar, and subbottom profiler to
successfully locate the abandoned materials. The results of the
geophysical survey were presented on a series of co-registered
maps that showed the distribution of surficial debris, buried
pipelines, sediment thickness and precision bathymetry.
Additional terrestrial survey work was done with fluxgate
magnetometers to locate buried wells on the beach.
URS/Greiner, Coeur D'Alene River, Kellog, Idaho, USA:
Since 1890 the mining industry has been disposing of mine
tailings into the Lower Coeur d'Alene River (LCDR). The EPA has
initiated a program to identify and map the lateral and vertical
distribution of these tailings in the LCDR and ten lakes located
along the river. Golder Associates conducted a geophysical
investigation, using subbottom profiling (SBP) and
ground-penetrating radar (GPR) methods at selected locations, to
evaluate their effectiveness for mapping these deposits. The
results of the geophysical investigation, supported by data from
sediment cores, indicated that GPR can be used to rapidly map the
mine tailings in the LCDR, and that SBP is more effective in the
lateral lakes. An extensive geophysical mapping program is being
planned at this time.
Beak Associates, Pt. Judith, Naragansett Bay, R.I., USA:
The grounding of a fuel barge in shallow water resulted in the
discharges of large quantities of petroleum. In order to assess
the possible damage to lobster habitat, and other biota in the
spill zone, it was necessary to map the sediment and surficial
features on the seabed. Golder Associates was contracted to
conduct a detailed side scan sonar survey of a 5 mile by 1 mile
area and to produce a mosaic of the seabed as part of the
investigation. Verification of the side scan sonar data was done
using underwater cameras that were lowered at selected locations
identified on the side scan sonar data. The side scan sonar data
were also used by divers to select sites for identifying and
quantifying the biota within the spill zone.
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