HYDRAULIC, MECHANICAL & SED-VAC DREDGING

PROJECT HIGHLIGHT

SHIPPING CANAL DREDGING & PCB SOIL TREATMENT
LAKE CHARLES, LA

  • 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.