Public water system · WA5340900
ActiveSammamish Plateau Water & Sewer
At a glance
Sammamish Plateau Water & Sewer (PWSID WA5340900) is an active community water system in King County, Washington. It reports serving 79,362 people through 24,792 service connections. Its primary water source is purchased surface water, and EPA lists it as owned by a local government. Of the 12 most recent violations in EPA's records, none is health-based, and the most recent began in January 2009.
This page covers its drinking water system only; sewer and wastewater service are not part of EPA's drinking water records.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
79,362
Service connections
24,792
Primary source
SWP
Purchased surface water
System type
CWS
Community water system
System record
How does Sammamish Plateau Water & Sewer compare with other water systems in King County?
By EPA's size categories, Sammamish Plateau Water & Sewer is a large system (10,001 to 100,000 people). King County has 214 active public water systems. Its population served is about 5.1 times the county average of 15,523 people per system, and accounts for 2.4% of the 3,321,960 people reported by systems filed under the county. Across Washington, the 4,705 active systems average 2,172 people each. Nationally, the average active community water system reports serving 6,703 people, so Sammamish Plateau Water & Sewer is about 12 times that figure.
What does “community water system” mean?
A community water system serves at least 15 connections used by year-round residents, or regularly serves at least 25 year-round residents. Homes, apartments and mobile-home parks are served by these. Washington has 2,392 active community water systems, 51% of the state's 4,705 active systems. Purchased surface water means the system buys surface water from another public water system rather than drawing its own. 130 Washington systems (2.8%) list purchased surface water as their primary source.
Who owns and regulates Sammamish Plateau Water & Sewer?
EPA lists Sammamish Plateau Water & Sewer as owned by a local government. The WA state drinking water program is its primacy agency, the regulator with primary enforcement responsibility for the system under the Safe Drinking Water Act. 58 of the 214 active systems in King County (27%) are also owned by a local government.
Does Sammamish Plateau Water & Sewer have drinking water violations?
Of the 12 most recent violations in EPA's records, none is health-based, and the most recent began in January 2009. The violations listed here began between January 2008 and January 2009. By type: 12 monitoring and reporting. The contaminant or rule involved most often is Nitrate (2 of them). EPA lists 10 as archived and 2 as resolved. Archived means the violation was not marked resolved but is more than five years past the end of the noncompliance period, so it no longer counts toward current compliance status. Resolved means at least one resolving action is on record: the system returned to compliance, the rule no longer applies, or no further action was needed.
| Began | Violation | Contaminant or rule | Health-based | Status |
|---|---|---|---|---|
| 2009-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Nitratecode 1040 | No | Resolved |
| 2009-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Nitratecode 1040 | No | Resolved |
| 2008-04-01 | Monitoring and reportingMonitoring, Regular · code 03 | Diquatcode 2032 | No | Archived |
| 2008-04-01 | Monitoring and reportingMonitoring, Regular · code 03 | Ethylene dibromide (EDB)code 2946 | No | Archived |
| 2008-04-01 | Monitoring and reportingMonitoring, Regular · code 03 | 1,2-Dibromo-3-chloropropane (DBCP)code 2931 | No | Archived |
| 2008-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Toxaphenecode 2020 | No | Archived |
| 2008-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Hexachlorobenzenecode 2274 | No | Archived |
| 2008-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Di(2-ethylhexyl) phthalatecode 2039 | No | Archived |
| 2008-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Simazinecode 2037 | No | Archived |
| 2008-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Lindane (gamma-BHC)code 2010 | No | Archived |
| 2008-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | 2,4,5-TP (Silvex)code 2110 | No | Archived |
| 2008-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Heptachlorcode 2065 | No | Archived |
The 12 most recent violations in EPA's records, newest first.Labels and codes come from EPA's SDWIS reference tables. A monitoring or reporting violation means a required test or report was missed or late; it does not by itself mean a contaminant was found. "Health-based" marks violations of a legal limit or required treatment.
Sammamish Plateau Water & Sewer: frequently asked questions
Who runs Sammamish Plateau Water & Sewer?
Sammamish Plateau Water & Sewer (PWSID WA5340900) is a community water system owned by a local government. It is regulated by the WA state drinking water program.
How many people does Sammamish Plateau Water & Sewer serve?
Sammamish Plateau Water & Sewer reports serving 79,362 people through 24,792 service connections in King County, Washington.
Where does Sammamish Plateau Water & Sewer get its water?
EPA SDWIS lists this system's primary water source as purchased surface water. Purchased surface water means the system buys surface water from another public water system rather than drawing its own.
Does Sammamish Plateau Water & Sewer have any drinking water violations?
Of the 12 most recent violations in EPA's records, none is health-based, and the most recent began in January 2009. A monitoring or reporting violation means a required test or report was missed or late; it does not by itself mean a contaminant was found.
Is Sammamish Plateau Water & Sewer's water safe to drink?
AquaCensus shows EPA compliance records, not current water test results, so it cannot say whether the water is safe at a given moment. Of the 12 most recent violations in EPA's records, none is health-based, and the most recent began in January 2009. For current results, consult the system's annual water quality report, EPA ECHO, or the WA state drinking water program.
Where can I find Sammamish Plateau Water & Sewer's water quality report?
As a community water system, Sammamish Plateau Water & Sewer must deliver an annual water quality report, called a Consumer Confidence Report, to its customers by July 1 each year, covering the previous calendar year. The system can provide a copy on request.
Other water systems in King County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| Seattle Public Utilities | King | 1,161,961 | Community | Surface water |
| Bellevue City of | King | 321,349 | Community | Purchased surface water |
| Kent Water Department | King | 166,421 | Community | Purchased surface water |
| Redmond Water System City of | King | 163,335 | Community | Purchased surface water |
| Lakehaven Water and Sewer District | King | 148,809 | Community | Purchased surface water |
| Renton City of | King | 108,091 | Community | Groundwater |
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About this data
Source: U.S. EPA Safe Drinking Water Information System (SDWIS) and SDWA violation records, via EPA ECHO, as published October 1, 2026 — AquaCensus refreshes it quarterly. See the methodology for how records are matched, cleaned and scored.
Cite as: AquaCensus, “Sammamish Plateau Water & Sewer, PWSID WA5340900, Washington”, https://aquacensus.com/water-systems/washington/sammamish-plateau-water-sewer-wa5340900 (data as of October 1, 2026).