North Sewer Service Area
Sewer Capacity Improvement Projects

These projects are designed to expand capacity of the sewer system
until the Sammamish Plateau Diversion is built.




Immediate, Temporary Improvements

Estimated Project Budget: $315,000  •  Estimated Project Timeframe: 2021-2023

Project Description

There are multiple improvements identified to improve capacity, located at three lift stations: Inglewood Lift Station, North Lake Lift Station, and Central Lake Lift Station.

Inglewood Lift Station Immediate Improvements: (1) - Reduce the pumping rate at Inglewood Lift Station during large storm events, to mitigate the peak rate of flow at North Lake Lift Station. This is an operational change to use smaller existing pumps. (2) - Provide 21,000 gallons of temporary storage. The storage will be provided by Baker Tanks that will be rented from between November and May during the 2021-2022 and 2022-2023 storm seasons. This storage would be utilized to buffer peak flows into the Inglewood Lift Station during periods when the pumping rate is reduced.

North Lake Lift Station Immediate Improvement: Install a portable Bypass Pump at North Lake Lift Station with higher pumping capacity than the current lift station pumps. The pump has been purchased by the District, and is expected to be delivered and available for use in November 2021. This pump may stay at the North Lake Lift Station site until the Interim North Lake Improvements have been completed.

Central Lake Lift Station Immediate Improvements: Provide 21,000 gallons of Temporary Storage. The storage will be provided by Baker Tanks that will be rented from between November and May during the 2021-2022 and 2022-2023 storm seasons. This storage would be utilized to buffer peak flows through the Central Lake Lift Station.

Additional Details and Status

Gray & Osborne worked in conjunction with District staff to identify temporary projects that could improve sewer capacity and be implemented in a relatively short time. The physical elements necessary to implement the Immediate Improvements have been ordered and are expected to be in place in November 2021. Additional details can be found in the PowerPoint presentation, "Immediate Temporary Improvements". PDF




Interim Central Lake Force Main

Estimated Project Budget: $1,096,000  •  Estimated Project Timeframe: 2021-2022

Project Description

This project is a portion of the interim project I-4, Phase 1 from the 2021 North Diversion Phase 1 Analysis. The Central Lake Sammamish Lift Station Force Main will increase the pumping capacity of the Central Lake Lift Station by providing a larger pipe that will have less resistance to flows. This project includes the installation of approximately 1,000 linear feet of 16-inch force main parallel to the existing 8-inch force main along East Lake Sammamish Parkway, from south of SE 33rd Street to SE 37th Place.

Additional Details and Status

Gray & Osborne has been hired to complete the project design, and this is currently ongoing. Construction is estimated to occur during the Spring and Fall of 2022.




Interim North Lake Lift Station

Estimated Project Budget: $4,229,000  •  Estimated Project Timeframe: 2021-2023

Project Description

This project is a portion of the interim project I-4, Phase 1, plus interim project I-2 from the 2021 North Diversion Phase 1 Analysis. The North Lake Sammamish Lift Station project will increase the pumping capacity of the North Lake Lift Station and also increase the storage available on the site. The pumping capacity will be increased by installing larger pumps and appurtenances, including a larger generator and upgrades to electrical and telemetry as required by the larger pumps. In addition, the wet well storage capacity will be expanded. The North Lake Lift Station is located at 426 East Lake Sammamish Pkwy SE.

Additional Details and Status

Gray & Osborne has been hired to complete project design, and this is currently ongoing. Construction is estimated to occur from Spring 2022 through Spring of 2023.




Interim North Lake Force Main

Estimated Project Budget: $5,420,000  •  Estimated Project Timeframe: 2021-2023

Project Description

This project is interim project I-4, Phase 2 from the 2021 North Diversion Phase 1 Analysis. The North Lake Force Main project extends the existing North Lake Force Main to bypass the Central Lake Gravity system, which limits the flow between the North Lake and Central Lake Lift Stations. The project includes installation of approximately 6,000 linear feet of 16-inch force main from the southern end of the existing 10-inch North Lake force main to and discharge directly to the Central Lake Sammamish Lift Station. This project location is along East Lake Sammamish Place SE from SE 21st (if extended) to SE 25th, where the force main continues along East Lake Sammamish Pkwy SE from SE 25th to 3350 East Lake Sammamish Pkwy SE.

Additional Details and Status

Gray & Osborne has been hired to complete project design, and this is currently ongoing. Construction is estimated to occur from Fall 2022 through Summer of 2023.




Interim North Lake Gravity Main

Estimated Project Budget: $3,717,000  •  Estimated Project Timeframe: 2023-2024

Project Description

This project is interim project I-4, Phase 3 from the 2021 North Diversion Phase 1 Analysis. The District’s sewer model indicates the gravity sewer main north of Louis Thompson Road may surcharge during large storm events. A flow monitor has been deployed to verify whether actual flow characteristics match the model results in this area. If the monitors indicate a surcharge does exist, and that surcharge is would cause operational problems, then the District will undertake the project to improve the gravity system in East Lake Sammamish Pkwy, generally between Inglewood Hill Road and Louis Thompson Road. The project would include the installation of approximately 400 linear feet of 18-inch and 2,500 linear feet of 21-inch gravity main.

Additional Details and Status

A monitor has been installed in the gravity main on East Lake Sammamish Pkwy north of Louis Thompson Road to measure the actual flows and flow depths in the sewer main. If needed based on the flow monitoring data, District would hire an engineer to complete design in 2023. Construction would be estimated to occur between 2023-2024.



How to contact the District. 

 

For builders and property owners with questions about affected sewer basins and/or details of the moratorium, please email District staff at ConnectionInfo@spwater.org.

Media inquiries: Please call or email the District's Public Information Officer at 425-392-6256 PIO@spwater.org.

Board of Commissioners

The Sammamish Plateau Water Board of commissioners meets on the first, second, and third Mondays of the month at 3:30 p.m. For information on attending or providing comment for an upcoming Board meeting, click here.

Ryika Hooshangi, President
Lloyd Warren, Vice-President
Mary Shustov, Secretary
Tom Harman, Commissioner
Nav Otal, Commissioner

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