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.
District Update
We have concluded sewer smoke testing for 2024. We use a harmless smoke injection process that gives us important information about the health of our sewer system with no threat to public safety. See smoke testing map below and link to learn more about this widely used technique. https://spwater.org/397/Sewer-Smoke-Testing
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: $1,326,072.33 • Estimated Project Timeframe: Completed
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 increasea the pumping capacity of the Central Lake Lift Station by providing a larger pipe that will have less resistance to flows. This project included 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.
Interim North Lake Lift Station
Estimated Project Budget: $6,021,111,78 • Estimated Project Timeframe: July 2023 - November 2024
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. Sammamish Plateau Water is upgrading the North Lake Lift Station, located at 426 East Lake Sammamish PKWY SE, to ensure continued high quality sewer service and meet the needs of our growing community. Permits and applications are approved or pending for the following upgrades to begin in September of 2023:
- New pump pit to house new 300 HP, 2,000 GPM capacity pump
- Existing dry pit will be converted to additional sewer wet well storage to increase capacity
- New standby generator building
- New odor control building Remodel of the electrical building
Additional Details and Status
Only minor traffic revisions will be required during the project which is expected to take 14 months to complete.
Interim North Lake Force Main
Estimated Project Budget: $5,435,000 • Estimated Project Timeframe: 2021-2024
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
Traffic revisions in place throughout construction period. Paving is anticipated for late August/early September. All 5,700 feet of new sewer line between East Lake Sammamish Parkway SE and East Lake Sammamish Place SE. has been installed and in service since October 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.
*NEW* Sammamish Plateau Diversion Project Updates
The Sammamish Plateau Diversion Project will create new infrastructure to manage some wastewater flows from the East Lake Sammamish area. Currently, wastewater flows from the Sammamish Plateau travel to South Treatment Plant in Renton. When the project is finished, a portion of those flows will travel north to King County’s Brightwater Treatment Plant.
See the latest news here.
Timelines for Important SP Water Sewer Issues
The Sewer Moratorium expired August 24, 2021
***No sewer overflows/failures have occurred.***
Projects in your neighborhood
We found solutions to expand capacity of the sewer system until King County brings additional regional infrastructure to the District. We expect some of the District-initiated solutions to come online by the end of this year, while long-term permanent improvements are built. Although the moratorium is no longer in effect, the District wants to reiterate that there were no sewer overflows or failures. Any statements or representations to this effect on social media or mailers distributed in the community are inaccurate and incorrect. Based upon the District’s understanding of growth projections for the City of Sammamish for the next 10+ years, the District has the sewer capacity to support additional growth.
On October 12, 2021, District staff presented an update to the Sammamish City Council at their request, regarding sewer capacity issues. The video of the presentation can be watched here.
The District is accepting connections again with an adjusted process, including a modified timing of payment of certain District fees as well as updated conditions to District-issued Certificates of Water and Sewer Availability. Updated forms can be found within the Builders/Developers area of our website.
Why did the District allow the sewer moratorium expire?
The decision to allow the sewer moratorium expire was based on internal analysis and assessments of several aspects regarding sewer capacity including:
- The identification of immediate and interim improvement projects that can increase capacity of the sewer system, and their anticipated time of implementation.
For individual project information, click here. - An analysis and understanding of the estimated timing of new connections based upon multiple factors including: previously issued Certificates of Sewer Availability, Developer Extension Agreements, and the average numbers of annual connections for properties transitioning from septic to sewer service.
- Ongoing efforts to identify potential sources of Infiltration and Inflow.
Your Sewer System is at a Crossroads.
Here's What's Happening.
If you’re a customer of Sammamish Plateau Water, or a party wishing to develop within our service area,you should be aware of King County’s decision to reduce in priority the building of much-needed and long-planned improvements to the regional sewer system, and the impact that decision has on our ability to meet the needs of current and future customers.
Overview
The District contracts with the King County Wastewater Treatment Division to send our wastewater to their regional facilities for treatment and disposal.
Since the District began providing sewer service, King County has planned on the sewer flow from the Sammamish Plateau to be divided:
- About half of the District’s wastewater would flow to the south around the south end of Lake Sammamish.
- The other half would flow north through a future-planned northern connection known as the Sammamish Plateau Diversion. See map 1
- See King County's website for this project here.
The District has designed its local sewer infrastructure anticipating a northern connection and for several decades has been giving King County notice that our facilities would be reaching capacity to continue to convey all sewerage to the one southerly regional connection.
The Issue. When do plans become a reality?
The District is outgrowing the capacity of the current sewer infrastructure. The District currently has only one connection point to the regional sewer conveyance system that is located in the southern portion of the District in the city of Issaquah. See map 2
Since the District has only this one connection point available to the regional sewer conveyance system, we have to direct all wastewater flows from the entire service area to this one connection in the south end.
The District is relying on King County to expand its regional conveyance system to include additional sewer infrastructure to meet our growing needs and to serve our current and future customer base.
This is not a new issue.
- For a number of years, the District has alerted the County that without the SPD, District facilities would soon reach capacity. We have now reached that point.
- In 2013, the District advised County staff of the urgent need to construct this long-planned expansion known as the Sammamish Plateau Diversion (a.k.a. "North Diversion" or "Northern Diversion").
- In 2016, the County advised the District that the Sammamish Plateau Diversion Project planning was underway, only to find out that in 2018, the County had removed the project from its Conveyance System Improvement Plan, citing funding limitations due to the operational failure of the County’s West Point Treatment Plant.
- The decision to deprioritize the Sammamish Plateau Diversion was made without notice or conversations with the District.
The Challenge. Regional growth mandates require regional sewer infrastructure.
Because the District contracts with King County for sewage treatment and disposal services, we are required to align our long-term sewage system plans with those of the County so that we can send our wastewater flows to the regional sewer conveyance system.
The District needs a second connection in the north to meet capacity needs and to serve its current and future customer base.
This second connection is a critical component of both the County’s and our long-term planning, and is key to following our District Wastewater Comprehensive Plan.
- To meet the needs of our growing service area, and comply with the County’s Growth Management Act, the District is required to provide water and sewer service to those areas of growth.
- This becomes more challenging without the additional capacity of a northern connection.
What’s at Stake? Sewer system capacity, resiliency, and the environment.
Limited options during an emergency
- An important benefit from having a second connection in the north would be the ability to route wastewater to that connection if the pipeline in the south is compromised during an emergency incident.
- Without having pipelines allowing for sewer flows to the north, the District is also placed in a position of increased risk for lengthy service disruptions from system failures, earthquakes, or other emergencies.
- These are the tough realities we face if the County does not authorize, fund, and build the improvements needed to meet the District’s regional sewer conveyance needs.
King County’s offer will impact ratepayers.
On March 22, 2021, King County Councilmember Kathy Lambert, along with King County staff, attended a regular meeting of the District’s Board of Commissioners.
During this meeting:
- In spite of planning coordination for decades and the County’s recognition that our local capacity constraints have been impacted by a lack of regional capital improvements, the County finally made an offer to share 50% of the costs with the District to construct improvements to the District’s local sewer system. While the offer is generous, it results in shifting of costs from the regional system to our customers due to the County’s untimely programming of needed improvements.
- County staff denied the District’s request to transfer District local assets to County ownership even though the District meets the County’s planning criteria. This denial perpetuates the District’s lack of equitable access to the regional conveyance system and continues to shift the cost burden to our customers for services that should be regionally provided and funded.
- The County indicated that it will be reprogramming its work on the Sammamish Plateau Diversion Project with completion anticipated in 2030, but similar to past efforts and representations, the County cannot give assurance that the work will be funded or completed.
The Board of Commissioners is currently reviewing the County’s offer but has placed priority on identifying local solutions because we need assurances that our conveyance needs will be addressed, and the best way to ensure that is to take the lead in finding solutions.
Here are the latest updates.
September 26, 2024: King County announces the County's Sammamish Plateau Diversion Project Team will be drilling along East Lake Sammamish Parkway Northeast on October 9, 2024 to sample soil and install groundwater monitoring wells. For more infirmation see the King County Sammamish Plateau Diversion webpage.
August 21, 2024: The City of Sammamish has approved the permit for King County’s Sammamish Plateau Diversion Project team to begin work on East Lake Sammamish Parkway Northeast.
July 31, 2024: King County notifies the community about field work that will take place along East Lake Sammamish Parkway Northeast. Currently, the county anticipates the work will begin later this summer. The county will provide details of this work, including work hours and closure details, as soon as the work schedule and permits are finalized. Please visit the Sammamish Plateau Diversion Project webpage for the most up-to-date information about this work, including when work will begin.
July 12, 2024: King County sends an email to residents about upcoming work happening along East Lake Sammamish Parkway Northeast. This work was expected to begin as early as the week of July 15th, but it is now expected to begin later in July. See email here.
October 12, 2021: District staff presented an update to the Sammamish City Council at their request, regarding sewer capacity issues. The video of the presentation can be watched here. The District’s presentation begins around the 5:15 mark of the Council meeting and the entire sewer capacity discussion concludes around the 1:15:00 mark.
August 24, 2021: The sewer moratorium expires and the District begins accepting connections again with an adjusted process, including a modified timing of payment of certain District fees as well as updated conditions to District-issued Certificates of Water and Sewer Availability.
July 16, 2021: In August, field crews will be conducting sanitary sewer smoke testing in selected areas of the District located within the North Sewer Service Area. For information about this project, including maps and neighborhood schedules, visit spwater.org/smoketesting.
June 14, 2021: The District received a letter from WTD Deputy Division Director responding to the District’s request for additional clarification about the County’s cost-sharing proposal.
June 11, 2021: The District received a letter from King County Executive Dow Constantine acknowledging the District's acceptance of the County's cost-sharing proposal.
June 7, 2021: District staff presented the Board of Commissioners with the Refined Scope of Work report for engineering services to address the sewer capacity issues in the North Sewer Service Area sewer system. The report includes information to support design of the interim improvements and management of the moratorium status. The District is also pursuing abatement (reduction) of Infiltration & Inflow (I&I) in the hopes of bringing additional capacity to the system.
May 24, 2021: The Board of Commissioners extended the sewer moratorium until August 23, 2021 to allow time to consider immediate, interim, and permanent improvements and their potential to provide additional capacity to the sewer system.
March 29, 2021: The Board of Commissioners held a Special Meeting and Public Hearing to receive public comments from the residents, businesses, and cities impacted by the sewer capacity issues and sewer moratorium enacted by the District. During the Special Meeting, the Board approved an engineering contract to identify and consider immediate, interim, and permanent improvements.
Follow these links to get additional facts.
View or download these supporting document files by clicking the corresponding links.
Maps
- Overview Map: Affected sewer basins during the 90-day moratorium. *The moratorium has since expired on 8/23/2021.
- Street-level Map: Affected sewer basins during 90-day moratorium.*The moratorium has since expired on 8/23/2021.
- Map 1: Location of proposed Sammamish Plateau Diversion (a.k.a. “North Diversion”)
- Map 2: King County Regional Conveyance System
- Map 3: Affected sewer service area
Correspondence
- 2021/Jun14 KC to SPW: From King County’s WTD Deputy Division Director responding to the District’s request for additional clarification about the County’s cost-sharing proposal.
- 2021/Jun07 KC to SPW: From Executive Constantine acknowledging the District's acceptance of the County's cost-sharing proposal.
- 2021/Apr30 SPW to KC: From District’s Board President to Executive Constantine accepting the County’s proposal, subject to additional clarification and agreement on terms.
- 2021/Mar22 KC to SPW: From the WTD Deputy Division Director to the District proposing a cost-sharing offer, committing to continue work on the Sammamish Plateau Diversion Project with completion anticipated in 2030, and denying the District’s request to transfer District local assets to County ownership.
- 2021/Jan20 KC to SPW: Dow Constantine committing to resuming work on the Diversion Project in 2021 and 2022, to “propose full funding for the project in the 2022-2024 biennial budget process” and “potentially purchasing a large portion of the District’s local system.”
- 2021/Jan05 SPW to KC: The District’s Board President expressing the District’s concern with “the County’s unilateral decision to deprioritize long-planned improvements to regional sewer conveyance infrastructure.”
- 2019/Jul24 KC to SPW: The District’s and County’s signed agreement for North Diversion Interim Improvements Study “to identify necessary improvements in the local sewer system related to the deferral of the King County Wastewater Treatment Division’s Sammamish Plateau Diversion regional conveyance system improvement project.”
- 2019/Apr16 SPW to KC: From the District’s Board President to the WTD’s Director including concerns that statements made in the County’s letter to the Mayor of Sammamish “discounts all of the Long-term collaborative planning efforts that have anticipated construction of a Northern Diversion and the financial investment the District has made anticipating a near term connection to the north.”
- 2019/Apr01 KC to COS: From King County’s WTD Director to the Mayor of Sammamish explaining the County’s decision to defer the Sammamish Plateau Diversion Project during the development of WTD’s 2019-2020 budget.
- 2018/Aug08 SPW to KC: From the District’s General Manager to the WTD’s Director responding to WTDs request for the District to participate with the County in conducting a consultant’s evaluation to update the District’s 2016 North Diversion Interim Improvement Evaluation Report.
- 2016/Sep26 SPW to KC: From District’s General Manager to the County sharing results of the Northern Diversion Interim Improvements Evaluation and expressing the need for the County to construct the Sammamish Plateau Diversion.
- 2014/May08 COS to KC: From the City of Sammamish’s City Manager to the WTD Director supporting the County’s plan for the Sammamish Plateau Diversion in order to “allow continued, uninterrupted development in our city, and avoid a potential moratorium” and “provide a vital benefit to our community.”
Other
- PDF Oct 12, 2021: PowerPoint presentation – North Sewer Service Area Status Update
- PDF Sep 13, 2021: PowerPoint presentation – Sewer Capacity Metrics
- PDF Aug 16, 2021: PowerPoint presentation – Process Modifications
- PDF Aug 16, 2021: Sammamish Plateau Water Board Resolution #5051 - Update to Developer Extension Agreement form, including modifications to timing of payment of certain District fees.
- PDF Aug 16, 2021: SPW Board Resolution #5050 - Updated conditions to District issued Certificates of Water and Sewer Availability.
- PDF Aug 2, 2021: PowerPoint presentation – Moratorium Queue (continued)
*The moratorium has since expired on 8/24/2021. - PDF Jul 26, 2021: PowerPoint presentation – Moratorium Queue *The moratorium has since expired on 8/23/2021.
- PDF Jul 26, 2021: PowerPoint presentation – Immediate Temporary Improvements
- PDF Jun 7, 2021: PowerPoint presentation - Refined Scope of Work Report
- PDF Jun 7, 2021: Refined Scope of Work Report - North Sewer Service Area
- PDF Jun 7, 2021: PowerPoint presentation - Infiltration and Inflow Abatement Options
- PDF May 24, 2021: SPW Board Resolution #5030 - Sewer Moratorium Extension *The moratorium has since expired on 8/24/2021.
- PDF May 24, 2021: Moratorium FAQs *The moratorium has since expired at on 8/24/2021.
- PDF May 17, 2021: PowerPoint presentation - Sewer Moratorium Discussion
- PDF Apr 19, 2021: SPW Board Resolution #5025 - Sewer Moratorium Amendment *The moratorium has since expired on 8/23/2021.
- PDF Mar 29, 2021: PowerPoint presentation from sewer moratorium Public Hearing *The moratorium has since expired on 8/24/2021.
- PDF Mar 12, 2021: Sewer Moratorium - Frequently Asked Questions *The moratorium has since expired on 8/23/2021.
- PDF Feb 22, 2021: Sammamish Plateau Water Board Resolution #5018 - Sewer Moratorium *The moratorium has since expired on 8/24/2021.
- PDF 2021 North Diversion Phase 1 Analysis
- PDF 2016 North Diversion Interim Improvement Evaluation
- PDF 2013 SPW Sewer Comprehensive Plan - Section 4.4 Future King County Facilities
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.
Nav Otal, President
Ryika Hooshangi,Vice-President
Mary Shustov, Secretary
Tom Harman, Commissioner
Lloyd Warren, Commissioner
