Bethel Bank Stabilization Bethel, Alaska

The City of Bethel operates a medium draft port that encompasses approximately 9,200 feet of shoreline. This port is a vital economic link for the community of Bethel and the village communities of the Yukon Kuskokwim River Delta and the adjacent Bering Sea coast.

The Bethel Bank Stabilization project consisted of the contractor installing rock riprap protection on 3,500 feet of unprotected riverbank and on 3,000 feet of previously installed bulkheads; installing tube steel "whales," tie rods, and pipe bulkhead; excavating and disposing of unprotected bank material; and excavating, sampling, and providing bioremediation of contaminated soils. The affected bank stretched for over 8,000 feet.

Over a 2-year period, we conducted a preliminary survey, seven interim surveys, and a final survey. The rock armor included several thicknesses of armor, a groin under the surface of the water, varying curves, and transitions and elevations that required extensive daily surveying and positioning. Bank surveys were conducted from 80-feet below the water surface to 40-feet above the water surface.

Soundings were collected with a singlebeam sonar system. Positioning was provided by a Trimble 4000 GPS receiver using Differential GPS (DGPS) techniques. Depths were corrected for tides using two Endeco tide gages. The uplands were surveyed using Real-Time Kinematic (RTK) GPS.

We used HYPACK hydrographic software interfaced with Trimble 7400 GPS receivers on-site. Data were reduced, computed, and plotted in TerraSonds' office.

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