Alpine recently completed a geophysical, geotechnical and environmental survey for TRC Environmental Corporation (TRC) related to Anbaric Transmission’s Vermont Green Line project in Lake Champlain. The proposed HVDC cable crosses approximately 40 miles of the lake from Beekmantown, NY to Ferrisburgh, VT.
Alpine mobilized its 45’ survey vessel R/V Henry Hudson to Lake Champlain from its home port in NJ. The R/V Henry Hudson was chosen due to its ability to provide both a good geophysical/hydrographic survey vessel and a sediment sampling platform. For the project, Alpine conducted high resolution multi-beam, subbottom profiling, side scan sonar imaging and magnetometry. In addition, Alpine conducted a series of short vibracores (6 feet) to ground truth the geophysics along the route and determine suitability for cable burial, and collected over 50 grab samples for both sediment classification and benthic analysis.
One of the challenges of the project was locating a suitable proposed route for cable installation across the lake. Lake Champlain varies in water depth significantly across its width and features steep slopes and depths along the route in excess of 400’. The geomorphology is also varied, ranging from areas of rocky bottoms and outcrops, to clay and soft silty sediments. In order to locate a viable, non intrusive route, Alpine reviewed the data on-the-fly in consultation with TRC, Anbaric and Caldwell Marine. Based on in-field assessments, alternative routes were chosen and surveyed in order to develop the ideal proposed route. This collaboration between interested parties, and the ability to quickly provide the client with data-based information required for rapid decision making, allowed a viable route to be located prior to demobilization and resulted in completing the survey and sampling effort successfully and on schedule.
We would like to thank TRC and Anbaric Transmissions for giving Alpine the opportunity to participate in this project and we would like to thank Caldwell Marine for their crucial input and route development advice in the field. We look forward to working with the Vermont Green Line Team as the project moves forward into its next phase.
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Alpine vibracores can be equipped with a high pressure water jetting system which virtually guarantees target sample recovery in most sediment.