Upper Pahsimeroi Fish Hatchery

Upper Pahsimeroi Fish Hatchery

May, Idaho

Deere & Ault Consultants, Inc. was part of a consultant team retained by Idaho Power Company for the planning, final engineering design, and services during construction for Idaho Power’s new Upper Pahsimeroi Fish Hatchery. Deere & Ault staff served as the overall project managers and prepared the design of the rearing units, buildings, yard piping and effluent treatment systems. The Pahsimeroi Fish Hatchery was a great success, with change orders totaling less than 1% of the final construction cost of $10 million.

Aerial view of the Upper Pahsimeroi Fish Hatchery.

Several buildings were designed on the Upper Pahsimeroi site including a 160 ft x 100 ft hatchery building containing incubation, early rearing troughs, cold storage, a laboratory, and office spaces. A combined administration building and bunkhouse provides working and living space for hatchery staff. The site also includes three well houses to protect the wellheads and pumps from the harsh winter conditions experienced in the Pahsimeroi River Valley.

Other structures on the site included a new intake channel and structure, two large outdoor extended rearing ponds covered by a 120,000 square foot metal building canopy, a pollution abatement pond, a 14,000-gallon aeration tower, and two outlet structures. A piping network connects river and groundwater supplies to the rest of the hatchery. Outdoor raceways had adjustable weirs and pipes to the outlet structures to allow for the volitional release of fish. Foundation drains were installed along all of the concrete basins to prevent uplift from the high groundwater on the site.

A thorough hydrologic analysis was performed in order to determine the flood risk to the site. A synthetic hydrologic record was created using data from the adjacent Lemhi River Basin to better determine the likely flood flows on the Pahsimeroi River. A HEC-RAS model was prepared to analyze the site, and the grading of the site was adjusted to protect all of the structures from high water.

Client: Idaho Power Company

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