Lake Ilo Dam Rehabilitation-Seepage Mitigation

In 2020, as part of a routine inspection, USFWS engineers documented seepage occurring on the downstream side of the Lake Ilo dam. After years of monitoring and evaluation, Tribal 1 was awarded this project, and successfully addressed critical seepage issues at the Lake Ilo Dam, a high hazard earthen dam structure within a protected wildlife refuge. Originally scheduled for 90 days, the team completed the critical Dam Safety repairs in 30 days, and final project in 60 days, thanks to innovative strategies and a collaborative approach.

Project Scope

• Installation of a deep trenched filter wall and blanket wall drain system to manage seepage from existing coal seams.
• Diaphragm filter installation around the outlet works conduit.
• Gate structure modification and inspection.
• Spillway cleaning and inspection.
• Structural concrete repairs.

Project Complexities and Solutions

• Schedule: The team completed the critical tasks in just 30 days, allowing USFWS to begin to raise the lake’s pool elevation ahead of schedule.
• Public Scrutiny: The draining of the lake along with the delays in repairs created significant public scrutiny making it critical to perform at an extremely high level of perfection.
• Cost Savings: Through value engineering and efficient project sequencing, Tribal 1 generated $180K in savings, directly benefiting the client, enabling them to award more critical option work.
• Safety and Environmental Sensitivity: Operating within a wildlife refuge required adherence to strict environmental protections and safety measures, resulting in a zero-incident safety record.