HYDRAULIC, MECHANICAL & SED-VAC DREDGING
SHIPYARD SEDIMENT CLEANUP & IMPROVEMENTS
PORT of EVERETT, WASHINGTON
- Demolition/disposal of the existing Travel Lift/Boat Haul-Out facility, marine railway,
and designated marina docks, floats, piles, gangways, and timber bulkhead elements
- Installation of a new sheet pile bulkhead and tieback anchor system along
bulkhead Segments A and B
- Excavation and landfill disposal of contaminated soil in Upland Area A
The Everett Shipyard Site Sediment and Central Marina Improvements – Phase I project was performed at the Port of Everett’s Waterfront Redevelopment area, an area of approximately 15 acres equally split between upland and marine acreage. In 2001, the Port of Everett began the waterfront redevelopment by removing several shipyard industrial buildings and a fisherman’s net shed. Various industrial activities over the past 120 years had left both soils and in-water sediments contaminated with a variety of petroleum and tar based contaminants that required removal prior to redevelopment.
The project included building demolition, contaminated soil excavation, marine demolition, storm water improvements, removal and replacement of a sheetpile bulkhead, and mechanical dredging of contaminated sediment. The project was performed in conjunction with Port’s ongoing Waterfront Place Central development which included bulkhead replacements, realignment of the marina, and construction of new public access amenities.
This project was the first major step in the redevelopment of Waterfront Place Central starting with the demolition and removal of boat haul-out facility, a marine railway that extended 200 ft underwater into the marina, several marina docks, floats, piles, gangways, and timber bulkheads. Great Lakes E&I also temporarily relocated and reinstalled several floats, piles, and gangways in new locations.
Once the in-water demolition and removal activities were completed, Great Lakes E&I installed 550 lf of new sheet pile bulkhead with a tieback anchor system along bulkhead Segments A and B. While the sheet pile construction was underway, mechanical dredging of the designated marine areas began. The dredging was accomplished using a barge mounted excavator equipped with an environmental clamshell bucket to minimize turbidity. DredgePack software was utilized to guide the dredging effort and maintain precise underwater grade control. Several multi-beam sonar bathymetric surveys were conducted to establish final contours prior to backfilling and capping the dredged areas. Approximately 8,426 cy of marine sediments were removed by mechanical dredging. Dredged sediments were loaded onto a barge then transferred to an upland staging area for dewatering prior to being shipped off-site for disposal. Approximately 12,000 tons of sediments were eventually shipped off-site for disposal.
Upland remediation included excavation, transportation, and off site landfill disposal of 6,616 tons of contaminated soil from Upland Area A. Great Lakes E&I also re-routed water, electrical, and storm drain lines and installed new storm drain outfalls through the new sheet pile bulkhead and into the marina. Work also included the installation of 400 LF of Combined Sewer Overflow (CSO) outfall, including all required bypass pumping and storm water management during construction. All water recovered during dewatering required pre-treatment through a water treatment system prior to discharge to the City of Everett.
The project was completed after placing and compacting 25,000 cy of clean backfill from onsite and off-site sources followed by site restoration including installation 2,500 lf of security fencing and 30,000 sf of asphalt paving. The project was a success by all measures in the eyes of the client, the Port of Everett.