Full Exclusion, Full Depth Fish Guidance Barrier Nets for Floating Surface Collector

Fish passage at high-head dams, from the reservoirs they impound to the rivers below, creates an engineering and biological challenge for migratory fish. The main purpose of high-head dams is water storage, allowing projects to reduce flood risk to downstream areas, provide water for domestic and agriculture purposes, provide

recreational opportunities, and generate hydroelectricity.

To return salmon populations to the watershed, Tacoma Power installed a Floating Surface Collector (FSC) at the Cushman Hydroelectric Project. To guide downstream migrating juvenile fish to the FSC, Pacific Netting Products designed a high-tech barrier net, blocking the fish from impingement or entrainment in the hydroelectric facilities. One NOAA fisheries scientist said, "it works like an extension of the shoreline, which the fish follow to the FSC". 

The collector puts a 150,000-pound load on the dam. A cutting-edge, shock-absorbing connection allows the FSC to roll, pitch, move up and down freely, and compress if needed. during extreme storm events. The FSC, and the "Net Transition Structure", are protected by debris and wave attenuation booms, designed by PNP to withstand epic storm conditions, and designed to operate within the entire reservoir operating range and allow employees to safely get on and off.

Once collected, fish are transported and released into the North Fork Skokomish River at the base of Cushman No.2 Dam, ultimately helping restore fish populations,  natural resource recovery and management goals on the North Fork Skokomish River. 

KEY FEATURES

  •  Nearly 500,000 sq ft of full exclusion guide net, the surface to the lake bottom
  •  Built with 1/8” x 1/8” and 1/4” x 1/4” Dyneema® netting
  •  Submersible boat gate allows for easy access for dam maintenance
  •  PNP wave attenuator:
  •  Protects the NTS and FSC
  •  Improves fish collection and survival
  •  Addresses extreme environmental conditions
  • Satisfies regulatory requirements