Restoring Water Flow: Advanced Silt Removal at Novelis

Silt accumulation can severely impact industrial water intake systems, leading to reduced efficiency and operational challenges. Underwater Construction Corporation (UCC) recently completed a comprehensive silt removal project at a Novelis intake structure in Oswego, NY, addressing significant sediment buildup and zebra mussel infestations. Novelis is a leading sustainable aluminum solutions provider and a world leader in aluminum rolling and recycling. This project showcases advanced silt removal methods and specialized equipment used to successfully restore optimal water flow.

In early 2019, Novelis encountered a critical issue: declining water flow from its offshore intake structure to the pump house wet well. UCC was contracted to investigate, uncovering an extensive blockage caused by zebra mussels and sediment buildup. This discovery launched a large-scale silt removal effort aimed at restoring full functionality to the intake system.

Upon inspection, UCC found the intake riser pipe entirely filled with zebra mussels, restricting water flow. Additionally, a remotely operated vehicle (ROV) inspection of the pump house wet well revealed obstructions and poor visibility, making assessment difficult. Addressing these issues required expert diving operations, specialized silt removal equipment, and careful structural considerations.

To tackle the extensive accumulation, UCC deployed a strategic approach:

• Diver-Assisted Removal: Conducted 133 dives to manually clear obstructions.
• Hydraulic Pumping: Used high-powered pumps to extract sediment and mussels.
• Geotube® Filtration: Processed and dewatered the extracted materials.
• Structural Reinforcement: Implemented modifications to ensure long-term functionality of the intake system.

Underwater Mineral Processing Services (UMPS), a division of UCC, played a crucial role by setting up a screening, dewatering and water treatment system adjacent to the pump house wet well. The extracted sediment was pumped into Geotubes for containment, while mussels and debris were separated and processed. All treated water was safely discharged back into the system, ensuring minimal environmental impact.

Effective silt removal requires not only extraction but also efficient processing and water treatment to minimize disruption and maintain environmental compliance. To achieve this, the project was executed in two phases, each designed to handle specific challenges at different locations within the intake system.

UMPS mobilized its advanced screening and water treatment system near the pump house. To enhance efficiency:

• Divers and a remotely operated robotic crawler dredge hydraulically conveyed sediment and debris.
• A recirculating pump system removed high-turbidity water, improving visibility for divers.
• Extracted material was dewatered in Geotubes®.
• Treated water was returned to the wet well to maintain operational efficiency.

To manage sediment and zebra mussel removal from the intake riser:

• A 2,000-gallon nurse tank was deployed on the UCC dive support barge for initial collection.
• A 1,000 GPM pump transported the material through a 1,400-foot pipeline to the shore-based UMPS treatment system.
• Screened zebra mussels and dewatered sediment were loaded into 25-cubic-yard roll-off containers for disposal at the Bristol Hill Landfill, ensuring environmental compliance.
• Treated water was safely discharged back into the pump house wet well, minimizing ecological impact.

Following the removal process, UCC reinforced the intake riser pump to prevent movement, which could have further disrupted water flow. When drilling to insert anchor rods into the bedrock, crews discovered voids filled with mud and mussels rather than solid grout. A secondary rigging solution was implemented, but due to casing degradation, its long-term effectiveness required ongoing monitoring.

Divers also used hydraulic saws and grinders to enlarge the riser pipe opening, improving water flow and access. A planned one-day outage allowed for a thorough inspection and cleaning of the pump bay, where 2 to 3 feet of accumulated sediment and steel debris were removed. The inspection revealed corrosion in steel structures, though they remained intact.

By leveraging specialized silt removal methods and equipment, UCC and UMPS not only restored Novelis’ water flow capacity but also implemented preventative measures to mitigate future risks. This project underscores the importance of proactive maintenance in preventing costly operational disruptions.

For industries facing similar challenges, UCC’s expertise in silt removal and underwater infrastructure maintenance offers reliable solutions to restore efficiency and prevent future blockages. Contact us today to discuss your project requirements and discover how we can meet your needs.