Green Harbor Maintenance Dredging

Green Harbor located in Marshfield, MA, is mainly used by small recreation and commercial fishing boats.  Maintenance dredging in the harbor was last performed in the 1980s and the entrance channel was last dredged in 2007.  A combination of the harbor’s entrance location, the poor condition of the protective breakwaters, and the ferocity and frequency in which storms continually move and redeposit sediments in the harbor's entrance channel and anchorage over the years have prevented most boats from being able to navigate the harbor during low tide.

The Project consisted of Dredging the Entrance Channel and Anchorage Area to depths of -8 and 6 feet at Mean Low Water, with 1-foot over-dredge allowance.  This resulted in removing an average of over 4 feet of material throughout the project site. CASHMAN DREDGING removed over 18,000 cubic yards of hard-packed sand from the Entrance Channels which was disposed at a nearshore disposal site just outside the west jetty.  Over 62,000 cubic yards of material, consisting of mostly mud, were removed from the Anchorage and Turning Basin Areas and were disposed of at the Massachusetts Bay Disposal Site, which is located approximately 12 miles off Salem, Massachusetts.


PROJECT HIGHLIGHTS

• Dredged ~100,000 yd³ with both near-shore disposal and off-shore disposal at the designated areas.
• The off-shore disposal area was located 22 nautical miles from the dredging area.
• The work was completed using the clamshell dredge Wood I with a combination of a 6-yd³ heavy digging bucket, a 14-cubic yard bucket for softer material, and a 3,000-yd³ split-hull barge.
• The Wood I and the scow Eddie Carroll were mobilized in November 2009, and dredging operations commenced; in January 2010, the dredge Wood II and the scow Mighty Quinn were utilized to clean up shoals in the Entrance Channel and the southern end of the Anchorage.
• Dredging operations were continually delayed by prolonged adverse weather conditions. Near the end of the Project, the USACE granted a one-week extension beyond the contract completion as a direct result of the delays caused by the adverse weather conditions during execution of the project. Despite losing over 30 days due to weather-related delays, the project was completed on February 5, 2010, just five days beyond the original completion date.