Frequently Asked Questions                                          

Who funds the project?

The project is partially funded by a $35 million infrastructure grant from the EPA (Environmental Protection Agency). The remainder of the funds are provided by the City of Seattle Combined Sewer Overflow Control Plan and King County's Comprehensive Water Pollution Abatement Plan. Total Project cost is estimated to be $130 - $140 million.

Construction of the City's Phase 1 project on Eastlake caused traffic problems and inconvenience for residents and businesses. Will construction impacts be better managed on this project?

The City and County are aware of community issues raised during the City's construction of Phase 1 and are committed to avoiding the problems that occurred. Appropriate construction constraints and restrictions will be incorporated into contract documents and will be enforced by City and County staffs. During construction, staff will share information with business owners on a regular basis to update them on construction scheduling, progress, and anticipated impacts.

Mercer Street is already a mess. What's going to happen to traffic when you start digging the tunnel?

The Mercer Street tunnel will be dug with a boring machine. Therefore, since there is no open trench excavation, the traffic interruptions on that street should be minimal.

What about traffic impacts to lower Queen Anne during festivals and events at the Seattle Center? In addition, there is a lot of construction planned at the Center. What is going to happen then with traffic because of this project?

In developing the construction schedule, we will work very closely with the Seattle Center regarding their events and planned construction. During any large events at the Center, our construction will be halted and roadways made as clear as possible to aid in traffic flow. We plan on taking the same comprehensive approach to other events in the area.

I understand that the plan is for the CSO Control Facility to be sited next to the West Farm Foods/Darigold plant on Elliott Avenue West. What will it look like?

The Elliott West site is currently about eight feet below the street grade of Elliott Avenue West. The site will be re-graded so that the future ground level will be at street level. The CSO Control Facilities will be partially underground. The above-ground structure will be 35 - 40 feet tall (above future grade). The above-ground facilities will be roofed, and architectural treatment and landscaping will be used to reduce the visual impacts from adjacent businesses, Elliott Avenue West, and Queen Anne Hill. A drawing of Facility and West Farm Foods plant is presented below.

With stormwater and sewage running through the Elliott West CSO Control Facility, won't there be a lot of odor?

To prevent odor problems during storms and when the facility is idle between storms, state-of-the-art odor control facilities will be installed at both the Control Facility and at the east tunnel portal in the South Lake Union area.

How will construction of the Elliott West CSO Control Facility be managed?

During construction, County staff will regularly share information with business owners and residents to update them on construction scheduling, progress, and anticipated impacts during upcoming weeks.

King County is working closely with SEATRAN to identify measures to ensure minimal disruptions to traffic on Elliott Avenue West during construction. These measures will be identified in detail as design progresses.

Will there be an odor issue at the outfall at Myrtle Edwards Park?

We do not anticipate that there will be. The outfall will regularly discharge 500 feet offshore into 60 feet of water. The one time a year (average) that untreated CSOs are discharged because of severe storm conditions, they will be discharged 100 feet offshore into 20 feet of water.

Will there be public access at the outfall location?

Yes. In fact, the 1% for art project is being focused at the Denny Regulator site, adjacent to Myrtle Edwards Park.

Will this project control the flooding we have experienced in our basements in the Westlake area in the past?

This project increased sewer system capacity and will reduce flooding during storms caused by system capacity limitations. Some street and basement flooding that occurs during heavy storms has other causes that were not addressed by this project. For example, side sewers serving businesses along Westlake Avenue North may lack capacity or be in poor repair, or catch basins may be clogged with leaves, litter, and debris resulting in flooding.

Customers experiencing flooding problems should contact Seattle Public Utilities Customer Service at 206-684-3000 during regular business hours. In the event of emergency flooding, call SPU Drainage Operations at the Dispatch Center, 206-386-1800, 24 hours a day.

Mara G. Rogers, public relations specialist
Seattle Public Utilities, 206-615-0866

How can I make sure that my business stays open and profitable during construction?

The County and City are working with businesses now to better understand how they may be impacted during construction. The more information we receive from these businesses early in the process, the better we will be able to plan for, design and schedule construction to minimize disruptions. If you have concerns about impacts to your business, please call 206/269-0229.

Will there always be water in the Mercer Street Tunnel? In what direction will it flow?

The tunnel will be dry unless there is a storm. The flow will run from east to west.

Does this new tunnel replace the old sewer lines along Mercer?

No, it does not. The old lines will continue in service during ordinary operations. The new lines and CSO facilities will be used only in a storm situation.

Will this project benefit King County Metro by enabling the West Point Plant to take additional flows from the developing areas in the northern part of the county?

No. This project serves only the immediate area in which it is located. It does not affect capacity in the rest of the system.

What about the noise from the equipment operating at the Elliott West site?

All of the equipment will be enclosed within the building. Furthermore, the pumps will be running only during storms.

For more information about the Denny Way/Lake Union CSO project,
contact Yvonne Kraus:

Phone: 206-269-0229
Fax: 206-269-0249
E-mail: e-mail

Yvonne Kraus
Norton-Arnold & Co.
1932 First Ave., Suite 510
Seattle, WA 98101

Updated: Dec. 11, 2003