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Community Water System · PWS WA5340900

Sammamish Plateau Water & Sewer

Sammamish, Washington 98075 - drinking water served from surface water sources to 79,362 people, tracked in EPA SDWIS and UCMR5.

79,362
People served
77
EPA violations
5
Health-based
6 PFAS
UCMR5 result

The verdict

EPA records 77 drinking-water violations at Sammamish Plateau Water & Sewer, 6% of them health-based - above the Washington per-system average, and UCMR5 testing detected 6 PFAS compounds.

77
Total EPA violations on record
6%
Health-based (MCL / treatment failure)
79,362
People served by this system
6
PFAS compounds detected (UCMR5)

Water Quality Snapshot: Sammamish Plateau Water & Sewer

Sammamish Plateau Water & Sewer is a local-owned community water system that delivers drinking water to 79,362 residents in Sammamish, Washington (King County) through 24,792 service connections. Its water is drawn from surface water sources. EPA's Safe Drinking Water Information System records 77 total violations for this system , of which 5 (6%) are health-based, meaning a contaminant exceeded an EPA Maximum Contaminant Level or a required treatment technique failed. A further 71 monitoring and reporting violations are on file. The most recent violation on record dates to 2009.

The most frequently cited contaminant at this system is Diquat, recorded in 10 violations (MR). Under EPA's UCMR5 PFAS monitoring program, 6 PFAS compounds were detected in samples collected from this system, with a maximum reported concentration of 16.5 ppt (parts per trillion). PFAS are persistent synthetic chemicals linked to health effects at very low exposure levels.

Across Washington, EPA tracks 4,557 public water systems serving 9,736,844 people, with 314,648 cumulative violations and 20,590 health-based violations on record. About 92% of systems in the state carry at least one violation, and state-wide the average per system is 69 violations. Statewide, 98 of 247 UCMR5-tested systems have reported PFAS detections (39.7%).

Sammamish Plateau Water & Sewer's 77 violations sit above the Washington average.

All figures above are sourced directly from EPA SDWIS and UCMR5 public data releases and are updated as EPA publishes new reporting cycles.

PFAS Detected

6 PFAS "forever chemicals" detected in testing under EPA's UCMR5 monitoring program.

Population Served
79,362
Total Violations
77
Health-Based Violations
5
Water Source
Surface Water

System Details

System Type
Community
Owner Type
Local
Connections
24,792
County
King
School/Daycare
No
MCL Violations
5
Monitoring Violations
71
Treatment Tech Violations
0

Violation History

Contaminant violations recorded by EPA.

Contaminant Category Count Latest
Diquat MR 10 2008
ETHYLENE DIBROMIDE MR 10 2008
1,2-DIBROMO-3-CHLOROPROPANE MR 10 2008
Coliform (TCR) MR 5 1995
Coliform (TCR) MCL 5 2004
Nitrate MR 2 2009
Pentachlorophenol MR 2 2008
Barium MR 1 2005
Mercury MR 1 2005
Dalapon MR 1 2008
Fluoride MR 1 2005
Chlordane MR 1 2008
Beryllium, Total MR 1 2005
Hexachlorocyclopentadiene MR 1 2008
LASSO MR 1 2008
Cadmium MR 1 2005
Picloram MR 1 2008
Methoxychlor MR 1 2008
Benzo(a)pyrene MR 1 2008
Heptachlor epoxide MR 1 2008
CYANIDE MR 1 2005
Atrazine MR 1 2008
Di(2-ethylhexyl) phthalate MR 1 2008
Di(2-ethylhexyl) adipate MR 1 2008
Endrin MR 1 2008
BHC-GAMMA MR 1 2008
Antimony, Total MR 1 2005
Dinoseb MR 1 2008
Gross Alpha, Excl. Radon and U MR 1 1979
Heptachlor MR 1 2008

PFAS Testing Results (UCMR5)

Results from EPA's Fifth Unregulated Contaminant Monitoring Rule. 24 of 464 samples detected PFAS.

Contaminant Date Result MRL Status
NMeFOSAA 8/7/2023 <6.00 ppt 6.00 ppt Not Detected
9Cl-PF3ONS 8/7/2023 <2.00 ppt 2.00 ppt Not Detected
ADONA 8/7/2023 <3.00 ppt 3.00 ppt Not Detected
PFHpS 8/7/2023 <3.00 ppt 3.00 ppt Not Detected
PFPeS 8/7/2023 <4.00 ppt 4.00 ppt Not Detected
NFDHA 8/7/2023 <20.00 ppt 20.00 ppt Not Detected
PFEESA 8/7/2023 <3.00 ppt 3.00 ppt Not Detected
PFMBA 8/7/2023 <3.00 ppt 3.00 ppt Not Detected
PFPeA 8/7/2023 <3.00 ppt 3.00 ppt Not Detected
PFMPA 8/7/2023 <4.00 ppt 4.00 ppt Not Detected
8:2 FTS 8/7/2023 <5.00 ppt 5.00 ppt Not Detected
4:2 FTS 8/7/2023 <3.00 ppt 3.00 ppt Not Detected
6:2 FTS 8/7/2023 <5.00 ppt 5.00 ppt Not Detected
PFBA 8/7/2023 <5.00 ppt 5.00 ppt Not Detected
PFUnA 8/7/2023 <2.00 ppt 2.00 ppt Not Detected
HFPO-DA 8/7/2023 <5.00 ppt 5.00 ppt Not Detected
NEtFOSAA 8/7/2023 <5.00 ppt 5.00 ppt Not Detected
11Cl-PF3OUdS 8/7/2023 <5.00 ppt 5.00 ppt Not Detected
PFHxA 8/7/2023 <3.00 ppt 3.00 ppt Not Detected
PFDoA 8/7/2023 <3.00 ppt 3.00 ppt Not Detected
PFDA 8/7/2023 <3.00 ppt 3.00 ppt Not Detected
PFOA 8/7/2023 <4.00 ppt 4.00 ppt Not Detected
PFOS 8/7/2023 <4.00 ppt 4.00 ppt Not Detected
PFNA 8/7/2023 <4.00 ppt 4.00 ppt Not Detected
PFHxS 8/7/2023 3.70 ppt 3.00 ppt Detected
PFHpA 8/7/2023 <3.00 ppt 3.00 ppt Not Detected
PFBS 8/7/2023 <3.00 ppt 3.00 ppt Not Detected
PFTA 8/7/2023 <8.00 ppt 8.00 ppt Not Detected
PFTrDA 8/7/2023 <7.00 ppt 7.00 ppt Not Detected
11Cl-PF3OUdS 6/26/2023 <5.00 ppt 5.00 ppt Not Detected
PFBA 6/26/2023 <5.00 ppt 5.00 ppt Not Detected
HFPO-DA 6/26/2023 <5.00 ppt 5.00 ppt Not Detected
ADONA 6/26/2023 <3.00 ppt 3.00 ppt Not Detected
9Cl-PF3ONS 6/26/2023 <2.00 ppt 2.00 ppt Not Detected
6:2 FTS 6/26/2023 <5.00 ppt 5.00 ppt Not Detected
PFUnA 6/26/2023 <2.00 ppt 2.00 ppt Not Detected
PFHxA 6/26/2023 <3.00 ppt 3.00 ppt Not Detected
PFDoA 6/26/2023 <3.00 ppt 3.00 ppt Not Detected
PFDA 6/26/2023 <3.00 ppt 3.00 ppt Not Detected
4:2 FTS 6/26/2023 <3.00 ppt 3.00 ppt Not Detected
PFOS 6/26/2023 <4.00 ppt 4.00 ppt Not Detected
PFNA 6/26/2023 <4.00 ppt 4.00 ppt Not Detected
PFOA 6/26/2023 <4.00 ppt 4.00 ppt Not Detected
PFHxS 6/26/2023 <3.00 ppt 3.00 ppt Not Detected
PFHpA 6/26/2023 <3.00 ppt 3.00 ppt Not Detected
PFBS 6/26/2023 <3.00 ppt 3.00 ppt Not Detected
PFPeS 6/26/2023 <4.00 ppt 4.00 ppt Not Detected
8:2 FTS 6/26/2023 <5.00 ppt 5.00 ppt Not Detected
PFHpS 6/26/2023 <3.00 ppt 3.00 ppt Not Detected
NFDHA 6/26/2023 <20.00 ppt 20.00 ppt Not Detected

Verify This Water System

The figures above are aggregated from EPA's public databases. To verify the underlying records, or to file a complaint, request a Consumer Confidence Report, or check current monitoring status, go directly to the federal and state regulators that enforce the Safe Drinking Water Act for Sammamish Plateau Water & Sewer.

Federal Source of Truth

EPA SDWIS, Federal Reports

EPA's Safe Drinking Water Information System (SDWIS) holds the federal compliance record for every regulated public water system. Open the system-level report by PWS ID:

View PWS ID WA5340900 on SDWIS

Source: EPA SDWIS Federal Reports Search

State Regulator

Washington Drinking Water Authority

Washington State Department of Health, Office of Drinking Water is the primacy agency that licenses and inspects Sammamish Plateau Water & Sewer under EPA-delegated authority.

Open WA regulator portal

Source: Washington State Department of Health, Office of Drinking Water

Violation Timeline

Each row links to the EPA SDWIS public record for verification. Cross-reference the contaminant code on EPA's federal report to see violation dates, return-to-compliance status, and enforcement actions.

Year (latest) Contaminant Category Count EPA Record
2009 Nitrate MR 2 SDWIS / WA5340900 / 1040
2008 Diquat MR 10 SDWIS / WA5340900 / 2032
2008 ETHYLENE DIBROMIDE MR 10 SDWIS / WA5340900 / 2946
2008 1,2-DIBROMO-3-CHLOROPROPANE MR 10 SDWIS / WA5340900 / 2931
2008 Pentachlorophenol MR 2 SDWIS / WA5340900 / 2326
2008 Dalapon MR 1 SDWIS / WA5340900 / 2031
2008 Chlordane MR 1 SDWIS / WA5340900 / 2959
2008 Hexachlorocyclopentadiene MR 1 SDWIS / WA5340900 / 2042
2008 LASSO MR 1 SDWIS / WA5340900 / 2051
2008 Picloram MR 1 SDWIS / WA5340900 / 2040
2008 Methoxychlor MR 1 SDWIS / WA5340900 / 2015
2008 Benzo(a)pyrene MR 1 SDWIS / WA5340900 / 2306
2008 Heptachlor epoxide MR 1 SDWIS / WA5340900 / 2067
2008 Atrazine MR 1 SDWIS / WA5340900 / 2050
2008 Di(2-ethylhexyl) phthalate MR 1 SDWIS / WA5340900 / 2039

How Sammamish Plateau Water & Sewer Compares

Cross-reference this system's record against state averages and the federal MCL framework for context.

Metric Sammamish Plateau Water & Sewer Washington avg Federal benchmark
Total violations 77 69 SDWA compliance, any non-zero count is a recorded breach
Health-based violations 5 4.5 Indicates a contaminant exceeded a federal MCL
PFAS detection 6 compounds 39.7% EPA final rule (2024): PFOA/PFOS MCL = 4.0 ppt
Population served 79,362 2,137 Sizing context for compliance burden

Sources: EPA SDWIS and EPA National Primary Drinking Water Regulations (40 CFR Part 141). State averages computed across 4,557 regulated public water systems in Washington.

Federal MCL reference, Safe Drinking Water Act thresholds ▼
Contaminant Federal MCL / Action Level Note
Lead 0 mg/L (Action Level: 0.015 mg/L) Lead and Copper Rule treatment technique
Arsenic 0.010 mg/L (10 ppb) Health-based MCL since 2006
Total Coliform Treatment technique (RTCR) Indicator organism, monitoring trigger
PFOA / PFOS (PFAS) 4.0 ppt each (final 2024 rule) Compliance deadline 2029 (EPA proposed extending to 2031, not yet final as of May 2026)
Nitrate (as N) 10 mg/L Acute health risk for infants

Frequently Asked Questions

Is Sammamish Plateau Water & Sewer water safe to drink? ▼
Sammamish Plateau Water & Sewer (PWS ID: WA5340900) has 77 recorded violations in the EPA SDWIS database. PFAS contamination has been detected in UCMR5 testing, with 6 PFAS compounds found. This system serves 79,362 people using Surface Water sources.
How many people does Sammamish Plateau Water & Sewer serve? ▼
Sammamish Plateau Water & Sewer serves 79,362 people in Sammamish, Washington. It is a Local-owned system using Surface Water water sources with 24,792 service connections.
What type of violations does Sammamish Plateau Water & Sewer have? ▼
Sammamish Plateau Water & Sewer has 77 total violations: 5 health-based violations (MCL exceedances or treatment failures), 71 monitoring/reporting violations, and 0 treatment technique violations. Health-based violations indicate contaminant levels exceeded EPA safe limits.
Has PFAS been detected in Sammamish Plateau Water & Sewer water? ▼
Yes. UCMR5 testing detected 6 PFAS compounds in Sammamish Plateau Water & Sewer's water supply: PFHxS, PFBS, PFPeA, PFPeS, PFOS, and others. PFAS are persistent "forever chemicals" that do not break down in the environment.
What water source does Sammamish Plateau Water & Sewer use? ▼
Sammamish Plateau Water & Sewer uses Surface Water as its primary water source. It is classified as a Community Water System (CWS), serving residential populations year-round.
Where does this data come from? ▼
All data comes from the EPA Safe Drinking Water Information System (SDWIS) and the UCMR5 PFAS monitoring program. SDWIS tracks compliance for all public water systems regulated under the Safe Drinking Water Act.
Data Sources: EPA Safe Drinking Water Information System (SDWIS), Q4 2025. PFAS data from EPA UCMR5 monitoring program (2023-2025). This data is provided for informational purposes only.

Read our methodology - how this data is sourced, computed, and verified.

Data sourced from EPA SDWIS and UCMR5 PFAS monitoring data. See our methodology for details. Retrieved and formatted by PlainWater Editorial

Every figure on PlainWater is rendered directly from EPA SDWIS drinking-water data, no number is typed in by an editor. This system's figures are rendered directly from EPA SDWIS data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.