Seattle, Washington: water and wastewater capital improvement projects
70 line items · $3.0B · starting 2026 · 2 plans
Seattle's published capital plans list 70 water, sewer and wastewater line items with a combined planning budget of $3.0B, of which 31 items worth $2.1B sit in the wastewater and sewer departments. The largest single item is Ship Canal Water Quality Project at $240M (2025–2028). The ten largest items are listed below; the full list with descriptions and page references is in Klarifi.
A capital improvement plan (CIP) is a city’s multi-year budget for building and replacing infrastructure. The water, sewer and wastewater sections list each project with its budget and the years it is funded, which makes them the earliest public signal that a plant, pump station or pipe network is about to be upgraded, usually two to four years before a contract is awarded.
The largest water and sewer projects in Seattle
| # | Project | Department | Type | Budget | Years |
|---|---|---|---|---|---|
| 1 | Ship Canal Water Quality Project | Sewer | Force mains and interceptors | $240M | 2025–2028 |
| 2 | Watermain Rehabilitation | Water Distribution | Water mains and distribution | $210M | 2025–2030 |
| 3 | Pipe Renewal Program | Sewer | Sewer rehabilitation and I&I | $197M | 2025–2030 |
| 4 | Combined Sewer Overflows | Sewer | Sewer rehabilitation and I&I | $184M | 2025–2026 |
| 5 | Shared Cost Projects | Wastewater | Stormwater and flood resilience | $176M | 2025–2026 |
| 6 | Future CSO Projects | Sewer | Stormwater and flood resilience | $176M | 2025–2030 |
| 7 | GSI for Protection of Beneficial Uses | Sewer | Stormwater and flood resilience | $125M | 2025–2030 |
| 8 | Distribution | Wastewater | Water mains and distribution | $119M | 2025–2026 |
| 9 | Sediment Remediation | Sewer | Stormwater and flood resilience | $117M | 2025–2030 |
| 10 | Transmission System Seismic Improvements | Water Supply | Water mains and distribution | $109M | 2025–2030 |
60 more line items in Seattle, with descriptions and contacts
Klarifi holds every Seattle line item with its description, the page it appears on and the source document, plus 3 verified contacts at the city’s treatment plants. Track new plans as they are adopted and compare with similar projects in other cities.
Planned spend by start year
Before 2026
$3.0B
68 items
2026
$1M
2 items
By department
| Department | Line items | Budget | Share |
|---|---|---|---|
| Wastewater | 13 | $658M | 22% |
| Sewer | 18 | $1.4B | 48% |
| Water Supply | 36 | $582M | 20% |
| Water Distribution | 3 | $298M | 10% |
Project types in Seattle's plan
Wastewater treatment plants in Seattle
2 publicly owned treatment plants in Seattle with 275 permit violations in the last three years. Each profile shows flow, permit, technology and compliance data.
| Plant | Avg flow (MGD) | NPDES | Violations (3y) |
|---|---|---|---|
| Metro West Point | — | WAL029181 | 275 |
| Salmon Creek WWTP | — | WAG994551 | 0 |
Other Washington cities with capital plans
Seattle capital plan questions
Sources and methodology
Budgets and years are as published in Seattle’s capital improvement plan or adopted budget. Klarifi extracts the water, sewer and wastewater line items from the published document, keeps the page reference for each one, and assigns a project type from the title and description with a keyword classifier. Figures are planning budgets, not awarded contracts, and can change when a plan is re-adopted.
Documents: Adopted Budget 2025–2026 (15 line items); CIP 2025–2030 (55 line items).
Data refreshed September 11, 2026.