Dredge Cell Engineering: Landfill Reuse

Navigational Dredging in Cocheco River

To assist the City of Dover (the City), in cooperation with the United States Army Corps of Engineers (USACE), in performing a navigational dredging project in the Cocheco River, GeoInsight prepared a comprehensive design and permitting package that was approved by the New Hampshire Department of Environmental Services (NHDES) as a win-win solution.  

Space in the cell for dredge spoil from this project was then contracted back to the USACE.  The City was able to realize additional return on its investment in the cell by selling space in the cell to other government entities and municipalities for disposal of sediment generated from other dredging projects.  GeoInsight was the engineer of record for the new cell, which covers a footprint of approximately five acres and has a capacity of approximately 100,000 cubic yards.  The spoil cell was constructed with a geosynthetic liner and underdrain system to collect and discharge sediment dewatering effluent to the City’s sanitary sewer system.

Project Sustainability Benefits

The project included numerous environmentally beneficial design aspects that help make it unique:

• The new dredge cell was situated on City-owned property located very close to the river, thereby minimizing hauling time and energy required to dispose of the spoils. 
• The cell was lined and situated over a previously-existing historic landfill, thereby providing a quasi cap over the old materials (uncapped refuse and dredge spoils). 
• The cell liner and effluent capture system took advantage of a nearby municipal sewer main by incorporating a short new connecting sewer line to properly manage the drained liquids.
• Portions of the berms were constructed using pre-existing natural features where ever possible, as well as existing acceptable historic waste materials (which in some cases required internal reinforcement).
• The cell was designed such that, at the completion of the project, it could be capped with a geosynthetic liner to prevent precipitation infiltration and potential direct contact with the dredge material, thereby facilitating reuse as the base for an athletic field.