Hydraulic & Mechanical Dredging

Forgen’s on-water dredging capabilities include hydraulic and mechanical dredging and the placement of subaqueous caps and covers. Most recently, Forgen team members completed a multi-year hydraulic dredging project on the Kalamazoo River removing oil-impacted sediment that resulted from a spill. This project was operationally active from 2012 to 2015 with a value of nearly $100M. Forgen’s patented Sed-Vac technology (U.S. Patent No. 7,526,884) is a unique system for removal of sediment and oil from water utilizing industrial cleaning technology. The use of an industrial vacuum loader allows sediment to be pulled from the affected area with little or no re-suspension of contaminated sediments. High pressure water is conveyed to the suction end of the vacuum pipe through flexible hose. The suction pipe is outfitted with high pressure nozzles that are angled toward the removal area. Hardened sediments are broken loose with the high pressure water and immediately vacuumed from the affected area.

Lake Charles, Louisiana

  • PCB contaminated soils dredging and treatment
  • GPS guided hydraulic dredging operations
  • Removal of 12,000 cy of non-tsca and 2,500 cy tsca impacted sediment
  • Onsite dewatering and treatment
  • Geotube sediment solidification

The Shipping Canal project involved the dredging of PCB-contaminated soils from a shipping canal at a carbon electrode facility. The sediment needed to be removed in accordance with an Administrative Order issued by the Louisiana Department of Environmental Quality. Several stakeholders were involved in the completion of this project and our crews interfaced with numerous client representatives and government entities.

Crews mobilized to the site and prior to dredging operations commencing, clearing and grubbing activities provided access to the construction area. This phase of the project involved removing brush, broken concrete, and debris piles. A sand subbase and berms were installed which provided a foundation for the construction of a HDPE liner. Due to the presence of underground utilities and unknown driveways, crews had to delay the installation of a water treatment system. To ensure the schedule was met, management implemented three design changes to keep operations on track. Throughout the initial phase of this project, crews also installed a drainage sand layer, Geotubes, dewatering pumps, and piping manifolds.

The dredging phase of this project began on February 16, 2014. Crews used a hydraulic cutter head guided by a GPS locator. The use of this system allowed for pinpoint accuracy when dredging to ensure that all specifications were met. The system removed 12,000 cy of non-TSCA material and 2,500 cy of TSCA-impacted material. The sediments were then pumped via a slurry line to a treatment facility that consisted of Geotubes. Once in the Geotubes, the material was dewatered. Unfortunately, the dredge slurry consisted of clay residual that had been dredged at depths that had been previously untested (due to the deep nature of the dredge patterns). Fine particles from the clay material encountered caused the Geotubes to leach water and the water treatment system to ooze clay. This was immediately addressed and the water treatment process was adjusted to handle the clay slurry.

Management assigned a crew to specifically monitor the water treatment system. Currently, Geotube removal has been delayed due to sediment consistency. Removal will resume once the sediment solidifies. At that time, the Geotubes will be split open and the sediment will be excavated and loaded into trucks to be hauled to an offsite disposal facility. The site will be cleaned and all equipment in contact with impacted sediment will be decontaminated.

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. Forgen also temporarily relocated and reinstalled several floats, piles, and gangways in new locations.

Once the in-water demolition and removal activities were completed, Forgen 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. Forgen 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.