Renovation of a water / sewer project in Seattle, Washington. Completed plans call for the renovation of a water / sewer project.

Question Deadline date changed from 09/19/2025 to 10/08/2025 as per Addendum 2 Response to Questions October 15, 2025, 11:59pm Interviews if Conducted (estimated) Week of October 27th, 2025. Announcement of Successful Proposer(s) November 18, 2025 Anticipated Negotiation Schedule November 18, 2025 Contract Execution December 5, 2025 Task 1 - Investigation and site characterization Objective: To develop an understanding of current site conditions and project risks based on available information and new sampling. Subtask 1.1 Documentation review - Consultant will gather and review existing data, including photographs, reports, data and drawings provided by Seattle City Light, historical site data from public sources such as aerial photography, Light Detection and Ranging (LIDAR), available survey and topographic data, and soil and geologic mapping. Identify gaps and additional information needs. Subtask 1.2 Site visits & sampling - Consultant will complete site visits as needed to perform sampling and any other data collection necessary to characterize contaminants of concern including determining approximate extent and quantity of contaminated materials. Including but not limited to water, exposed surfaces, and tunnel floor. The consultant will identify a plan for characterization of the site, including whether the consultant plans to use divers, Remote Operated Vehicles (ROV), or temporarily dewater the tunnel. Associated safety plans will be required. Temporary dewatering methods must be approved by the Department of Ecology. Task 2 - Options analysis for the tunnel dewatering and environmental cleanup Objective: Research and recommend potential project approaches that will meet the objectives of the project including: o Remediate or mitigate contaminants from the water and tunnel including dissolved, suspended, and solidified contaminants without contaminating Diablo Lake. This requires a long-term solution. o Dewater the tunnel for short-term investigation/mitigation activities and for long-term operations and maintenance activities using a method(s) that can be approved by Department of Ecology. Complete appropriate sampling and validation of any water treatment systems planned for temporary or permanent dewatering systems in accordance with Department of Ecology requirements. o Evaluate existing system and design temporary and permanent dewatering systems that will maintain the dewatered state long-term while meeting water quality standards with similar capacity and a high degree of reliability. The permanent system will be designed to City Light's specifications, which will include but is not limited to operation indication visible at the powerhouse, run-time logs, tunnel water float switch/level sensor, and flow meter, which can input to City Light's Supervisory Control and Data Acquisition (SCADA) system. o Leave the site in a state that meets workplace standards for entry with regard to contaminants present and prevents migration of contaminants out of the tunnel.