General Construction Company was selected to maintenance dredge the Day Island Yacht Harbor Marina. Dredging included about 6000 cy of material from the marina. We also installed new galvanized steel pipe guide piles for the new dock sections as well as new ACZA treated wood pilings as reinforcement for a nearby bulkhead.
PM Reality (agent for City of Alameda) contracted General Construction for this maintenance dredging job. General's own DB Oakland and Dump barge, using a 16 CY bucket, performed the dredging. Dredged material was passed through a screen to remove any material prior to sending the barge off for aquatic disposal at the designated dump site.
For this fast-track environmental and navigational dredging project, General remediated contaminated sediment and also deepened Sinclair Inlet for a new carrier pier. We dredged an underwater disposal pit, then placed 510,000 cu yd of contaminated material in it before capping it with clean sand. We also dredged 675,000 cu yd of clean sediment which was placed in in the deep water dispoasl site. Two environmental buckets, 24 cu yd and 27 cu yd, three split hull dump barges, differential GPS, and an electronic tide gauge were utilized to complete the work.
The project removed approximately 5,000 cu yd of contaminated sediments adjacent to the Norfolk combined sewer overflow outfall on the Duwamish River. The location, trapped between two low level fixed bridges, required installation of a temporary trestle to mobilize a 125-ton crawler crane onto a special barge with containment cells and anchor winches. All materials were mechanically dredged according to a detailed contour plan requiring 2-4 ft cuts.
The first phase consisted of the construction of a habitat area by building an underwater rock berm from elevation -50 ft MMLW to elevation -20 ft MMLW. The area behind the berm was backfilled with 84,000 cu yd of dredge spoils. The second phase required the dredging of 392,000 cu yd of material and placement of riprap slope protection. There were 43,000 cu yd of unsuitable material that was excavated and disposed of at a designated landfill.
The project began with the relocation of approximately 1,000 sq ft of eelgrass. Then a 250ft long by 50 ft wide trench was dug. Serving as a foundation for the diffuser, three, 4 ft by 12 ft articulated concrete ballast mats were placed at in 55 ft of water in Puget Sound. The 620 ft. long, 54 inch HDPE outfall pipe was sealed at each end and pulled from the beach into the water. While it was floating, 23 concrete weights were attached. Each weight was over 15,000 pounds. After attaching the onshore end to its tie-in point, we used controlled submergence to sink the pipe into the trench and onto the mats. Finally the trench was backfilled and the beach was restored to its previous appearance.
This project was an environmental cleanup of a Superfund site. Dredging and sediment dewatering were carefully planned and executed to avoid spreading contamination during the work. Additionally, the project included demolition of 105,000 sq ft of pier decking and removal of 2,600 timber piles. 90,000-tons of slope rock and under pier capping sand were installed. The Association of General Contractors of Washington honored this project with the 2006 Construction Excellence Grand Award.
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Federal Way, WA 98003
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