Sanpoil River Assessment

The Confederated Tribes of the Colville Reservation (CCT) are developing strategies for the reintroduction of juvenile Chinook salmon above Grand Coulee Dam, including the development of acclimation facilities and/or a hatchery along the Sanpoil River.

As a subconsultant to an environmental partner, GSI completed an initial hydrogeologic and groundwater supply assessment, including the evaluation of site attributes and characteristics of a hatchery property located on the Sanpoil River near the Louie Creek confluence. We evaluated the existing groundwater source supply as a viable water supply alternative for the hatchery development project and helped determine whether hatchery production at the property site might be feasible, including the potential type and design of a facility. The objectives of the groundwater analysis work were to: (1) determine the potential yield of an existing domestic supply well, (2) evaluate the suitability of groundwater and surface water quality for Chinook rearing, and (3) evaluate the capacity potential of a larger production well(s) on the property.

Although surface water and groundwater quality at the site was determined to be generally suitable for fish culture, GSI found that there was critical uncertainty regarding the potential yield of additional wells developed at the site (with respect to the initially targeted production rates), and potential for thermal breakthrough (i.e., increased water temperatures) in the aquifer with increased pumping. We then developed strategies for next steps and costs for a test/production well program to evaluate the overall site groundwater supply yield, assess the potential for thermal breakthrough while incrementally developing supply capacity, and mitigate other uncertainties discussed in the initial assessment. The CCT is assessing costs and funding for completing this next phase of the evaluation.

GSI's work involved:

• Project management and coordination with stakeholders, teaming partners, and subcontractors.
• Reviewing available local hydrogeologic data and well construction reports.
• An assessment of existing domestic water well, including pumping test.
• Field monitoring of water levels, pumping rates, and field water quality parameters.
• Analysis of surface water and groundwater quality results.
• Developing planning-level costs for test well and/or production well.