Resources and Materials

Enloe Dam Removal Feasibility Study:

The Enloe Dam Removal Feasibility Study has now been completed. The study concludes that dam removal is feasible but does not represent a final decision or commitment to construction. There are many necessary steps left in the planning process to clarify key aspects of such a project and support future decision-making. The project team is taking these necessary steps as we advance the designs to the 30% level.

Link to Materials

Additional Studies in Support of 30% Engineering Design and Permitting:

The Feasibility Study identified several additional studies and analyses needed to further inform project planning and advance the project toward a 30% level of design. This work includes additional characterization of reservoir contaminants; updates to hydrology, hydraulics, sediment transport, and sediment fate models; and assessment of potential impacts to downstream water users and irrigation infrastructure. Together, these studies provide additional information to better understand potential project impacts, identify opportunities to reduce or mitigate those impacts, and inform the next phase of project design.

  • Summary of Elutriate Toxicity Testing Results – Enloe Dam Removal Project

    This addendum provides additional information on the toxicity of sediments impounded behind Enloe Dam. It supplements data and findings presented in the Enloe Dam Sediment Evaluation Report.

  • Irrigation Infrastructure Impact Assessment - June 2026

    Prepared by the Okanogan Conservation District for Trout Unlimited, this assessment looks at how potential Enloe Dam removal could affect irrigation infrastructure and water users along the Similkameen and Okanogan rivers. Through targeted outreach and surveys of individual water users and water purveyors, the assessment identifies potential vulnerabilities related to increased sediment, estimates possible maintenance impacts, and outlines considerations for mitigation, monitoring, and continued coordination as project design advances.

    • Irrigation Infrastructure Impact Assessment -Appendices

      These appendices provide the supporting materials and data used in the Irrigation Infrastructure Impact Assessment, including questionnaires for individual water users and water purveyors, survey results, outreach materials, landowner and irrigator letters, and study-area maps. Together, they provide additional detail on the outreach process and community input used to inform the assessment.

Resolutions

Background Studies and Technical Material

  • United States Geological Survey Sedimentation Study

    • 2019 USGS survey of the Enloe Dam reservoir that revealed elevated trace element concentrations, notably arsenic, associated with historical mining activities and ore-processing waste within the sediment behind the dam.

  • United States Geological Survey Sediment Volume Work

    • USGS study regarding the concentrations of contaminant trace elements and sediment volume estimates behind the Enloe Dam.

  • Washington Department of Ecology Sedimentation Study

    • 2023 ECY study on sediment samples from the Enloe Dam reservoir and downstream areas that revealed elevated levels of arsenic and sulfide, particularly along certain transects, indicating localized contamination in the reservoir sediment.

  • Water and Power Law Group Memorandum

    • Report describing a feasible pathway to pursue removal of Enloe Dam in cooperation with Okanogan Public Utility District (PUD), the dam owner. The report analyzed potential liabilities arising from dam removal, along with strategies to avoid and manage such liabilities.

  • 2023 Enloe Proviso Report

    • Report that outlines a series of assessments to analyze the steps and options for potentially removing Enloe Dam on the Similkameen River in Washington. The assessments include developing a dam removal road map, recommending a collaborative engagement framework, assessing potential Dam Removal Entities, and reviewing sediment removal options.

Feasibility Assessment Studies

2024 Sensitive Plant Survey of the Enloe Impoundment/Lake Vegetation by Dana Visalli