Cle Elum Dam Fish Passage Facility

The Problem

Construction of a new adult fish collection facility at Cle Elum Dam required deep excavation in saturated soils directly adjacent to the existing concrete stilling basin and the Cle Elum River. Site conditions presented an extreme groundwater challenge: without continuous dewatering, the excavation could flood within 2–4 hours, and differential groundwater pressure between the surrounding soils and the open stilling basin risked basin flotation and structural failure to the existing dam infrastructure.

JDC's Solution

The Bureau of Reclamation designed the dewatering system, specifying well depth, spacing, and layout. Jensen Drilling Company furnished all materials, drilled, installed, developed, and operated the full system — including all primary deep wells, observation wells, and all supplementary wells as directed. Every well was required to be installed and fully operational before the September 1st in-river work window. Redundant contractor-supplied generators with automatic failover ensured no single power failure could stop dewatering operations.

Customer Benefit

Jensen Drilling Company maintained continuous 24/7 dewatering operations throughout the entire in-river construction window, ensuring the stilling basin differential pressure requirement was met at all times. This protected the existing dam structure from flotation risk and allowed the general contractor to safely complete all Stage 1 concrete, fish screen installation, and facility construction within the constrained in-river work period — supporting a critical fish passage restoration milestone for the Yakima River Basin.