Periodic Inspection of St. Paul Harbor Breakwater, Alaska

摘要

Under the Periodic Inspections Work Unit of the Monitoring Completed Navigation Projects Program, precise position data have been re-established for the above-water armor stone on the St. Paul Harbor breakwater extension and compared with data obtained previously. The positions of the armor stone layer over the 320-m (l,050-ft) length of the breakwater extension was defined through limited ground surveys, aerial photography, and photogrammetric analysis. Contour maps of the breakwater as well as cross sections of the structure were developed. In addition, a database of broken armor stones was updated. Results of the monitoring indicated that essentially no change in the overall breakwater crest elevation and shape of the structure had occurred since the last inspection of l996. There were localized areas of the breakwater, however, where void has occurred (likely due to displacement of armor stones). The rate of stone breakage also appears to have declined since the last survey. The site will be revisited periodically in the future and the long-term structural response of the breakwater to its environment will continue to be tracked. The periodic data sets will be used to improve knowledge in design, construction, and maintenance of the existing structure as well as proposed future coastal projects.