Kelsey Creek/Lake Hills Culvert Project

The Kelsey Creek Culvert at Lake Hills Project is in east Bellevue, near Larsen Lake and the Lake Hills Greenbelt. Lake Hills Boulevard runs through the project area, and its annual weekday traffic is more than 10,500 vehicles.

There have been a number of drainage and flooding issues in recent years, including a water main break in the Federal Field parking lot, concerns about the capacity and instability of the Kelsey Creek culverts and significant maintenance needs for other sewer pipes in the area. To minimize disruption on the surrounding community, improve efficiencies between systems and keep costs down, the City will address all of these issues at the same time.

The project goal is to develop a comprehensive solution for the Kelsey Creek culvert, Federal Field parking lot sewer and water pipes, and sewer pipes next to Federal Field.

The project team conducted a thorough environmental review in developing the design alternatives for review. The alternative chosen will:

• extend the lifespan of the pipes and improve reliability
• reduce operations and maintenance needs
• improve fish passage in Kelsey Creek

This project is in the alternative analysis phase, which is when the team develops several options to solve the problem and ultimately selects one alternative that meets the project technical needs, is within budget and minimizes impacts on the community. Design will begin after the alternative has been selected, which is anticipated for early 2022. Construction is anticipated for 2024.

This fall, the design team developed 3 alternatives to evaluate. Each alternative is designed to solve the flooding and reliability problems in a unique way.

Each alternative must:

• Work – the most basic criteria, the alternative must work technically to solve the problem
• Be permittable – several regulatory agencies have jurisdiction in the area, and the selected alternative must meet permitting requirements
• Fit within budget
• To the extent possible, minimize impacts to the community

Because of the nature of the project area, there are a few specific technical issues the team will plan around, including:

• Minimizing conflicts with existing utilities, like fiber optics, cable, natural gas, and sanitary sewer lines
• Instability of peat soils in the project area and potential need for additional structural support
• Operations and maintenance needs

Working with all of these criteria and design considerations in mind, the team developed alternatives A, B and C, shown in the following sections.

Alternative A

In this project approach, the City would:

• Replace the current stream crossing structure (culvert) with a larger culvert in the same location.
• Relocate the water main to the north and above the new culvert.
• Construct a sewer pipe that will cross beneath the culvert.
• Raise the level of Lake Hills Boulevard.
• Alternative would result in minimal changes to the existing stream channel or surrounding habitat.

Alternative B

In this approach, the City would:

• Construct a larger culvert to replace the current culvert, west of the current location.
• Relocate the water main to the north and above the new culvert.
• Replace the current sewer pipe with a larger pipe.
• Re-align the Lake Hills Greenbelt Trail.
• Slightly raise the level of Lake Hills Boulevard and Federal Field Parking Lot.
• Realign Kelsey Creek to the west of its current location in the Lake Hills Greenbelt.

Alternative C

In this approach, the City would:

• Construct multiple channels and culverts to replace the current culvert.
• Relocate the water main to the north and above the new culvert.
• Potentially replace the existing sewer pipe with a larger pipe.
• Potentially raise the level of Lake Hills Boulevard and Federal Field Parking Lot.
• Reconstruct the existing stream channel with two channels within the Lake Hills Greenbelt to provide enhanced fish and wildlife habitat.