SACRAMENTO REGION, CA (MPG) - A two-year, $9.7 million project extending Nimbus Hatchery’s famous fish ladder into Nimbus Basin is half complete. The hatchery’s 65-year-old ladder will soon serve for a final season and the new passage will open next summer.

Existing hatchery steps rise for a fraction of the 1,900ft channel currently under construction. Via a circuitous route, the new piscine freeway will conduct Chinook salmon and steelhead to hatchery processes that began after Nimbus and Folsom Dam were built. In the Department of Fish and Wildlife facility, eggs and milt are harvested for artificial fertilization. Edible fish meat is saved for food closet distribution and in spring, millions of fry are released. Once endangered, Chinook adults now return in reliable numbers for fall breeding.

The current ladder system employs connected pickets to divert fish to hatchery steps. Though many adults spawn and die before reaching this weir, the altered American River provides insufficient breeding sites. In mitigation, many thousands of salmonids are annually processed at Nimbus. Hell-bent on reproduction, their end-of-life journey through Carmichael, Fair Oaks, Rancho Cordova and Gold River provides an autumn spectacle for nature lovers. In preparation for the 2020 run, weir pickets were recently lowered. When water temperatures reach November frigidity, ladder gates will open and the hatchery’s vital work will resume. 

Upstream, the new ladder entrance has already been built. Engineered by the Bureau of Reclamation, the massive extension project begins near the south side of Nimbus Dam. Migratory fish will next year gain an extra quarter-mile of river for natural spawning; those that reach the dam unfulfilled will be lured by churning water to a rock-lined flume. Swimming gradually uphill, they’ll encounter a pond and steps. Lookouts (including an underwater window) will enhance visitor views. “We’ve wanted a submerged window for ages,” approves Nimbus interpretive specialist Laura Draft. “Fish anatomy and adaptations are more visible underwater. This makes for more exciting visitor experiences.”

The Roseville-based firm of J.R. Conkey heads the construction. Syblon Reid contractors (Folsom) will pour 2,030 cubic feet of flume concrete. Oaks and cottonwood trees in the four-acre project area have been largely preserved.  This piscine freeway will pass under Hazel Bridge, paralleling a realigned bike trail. Banks between the hatchery and the dam are already permanently closed to anglers. A future program will augment Nimbus Basin shoals to encourage natural spawning.

The autumn phenomenon of massive Chinooks challenging the hatchery weir will end when this aging barrier becomes redundant and is removed. BLR project manager Mark Curney welcomes the eventuality. “The weir has maintenance and safety issues,” he explains. “In years with big storm flows, serious damage has occurred. We’ve had to reduce river flow for up to five days for repairs. Our project will improve public and employee safety. It will also reduce costs and increase the hatchery’s operational flexibility.”

Nimbus Hatchery is located at 2001 Nimbus Rd, Gold River. Due to COVID restrictions, operations are now closed to the public. Facility parking is open and the 2020 salmon-run may be viewed from walking trails. Limited ladder viewing is possible from November to March. For more information, visit: www.wildlife.ca.gov/fishing/hatcheries/nimbus.