Wanapum Future Units fish bypass

Image courtesy Grant County PUD No. 2
The Wanapum fish bypass is being built in an area of the dam originally slated for future turbines.

Project description:

The Wanapum Future Units bypass project will protect salmon and other fish by allowing them to bypass the dam and its turbines, which can be deadly.

The new bypass should be finished in time for the spring migration of juvenile salmon down the Columbia River. The new bypass is being constructed though an area of the Wanapum Dam known as Future Unit 11: an area that was originally constructed and set aside for the purpose of adding more turbines at a later date.

Instead of housing new turbines, Future Unit 11 is being altered for the new fish bypass. Construction involves removal of the existing intake concrete and replacing it with a new ogee curved spillway surface. This process requires excavating 14,000 cubic yards of material for a foundation and pouring about 40,000 cubic yards of new concrete to complete the structure.

The fish bypass will also use large gate structures, which can open and close using two sets of large hydraulic cylinders. About 1.2 million pounds of steel will be required to build the large gates and their structures.

Once completed, the new spillway’s opening will be approximately 18.5 feet wide and 42 feet high, with the spillway extending 160 feet downstream from the dam, with a total length of approximately 300 feet. The lower portion of the bypass chute will widen to approximately 90 feet at the discharge to the Columbia River.

The bypass design was chosen after repeated tests of other fish-friendly systems: bottom spill systems, bottom-to-top spill conversion bulkheads, attraction flow channels and intake diversion screens.

Address: Wanapum Dam, Ellensburg

Cost: $29.45 million (award amount)

Type of contract: Hard bid

Start of construction: August 2005

Expected completion date: April 2007

Contractor: General Construction Co.,
19472 Powder Hill Place,
Poulsbo, WA 98370,
(360) 779-3200

Design: Jacobs Civil,
600 108th Ave. N.E., Suite 700,
Bellevue, WA 98004, (425) 452-8000

Owner: Grant County PUD No. 2

Project participants:

Bar M Steel Commercial — Bluegrass Bit Co. — Burke Electric — Central Pre-Mix Concrete Co. — Global Diving & Salvage — IIHR–Hydroscience and Engineering — Oakwood Consulting

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