D21/100
SAMMAMISH PLATEAU WATER & SEWER — Water Quality Report 2026
Serving 79,362 people · Washington
Water Source
Purchased Surface Water
County
—
System ID
WA5340900
Violations
53
Contaminant Test Results
3 contaminants above EPA health goals
| Contaminant | Detected | Limit (MCL) | Status |
|---|---|---|---|
Copper (90th percentile) | 3.80 mg/L | 1.30 mg/L | Over Limit |
chlorate | 265.00 µg/L | — | Above Goal |
Lead (90th percentile) | 0.002 mg/L | 0.015 mg/L | Above Goal |
EPA Violation History
No violations in the past 5 years
Full EPA compliance since 2009.
Understanding violation severity
Tier 1Urgent health risk. Utility must notify all customers within 24 hours.Tier 2Important health or treatment issue. Customers notified within 30 days.Tier 3Administrative or monitoring issue. Reported in the annual water quality report.
Source: EPA Safe Drinking Water Information System (SDWIS) · Updated quarterly
Frequently Asked Questions About SAMMAMISH PLATEAU WATER & SEWER
Is SAMMAMISH PLATEAU WATER & SEWER water safe to drink?
SAMMAMISH PLATEAU WATER & SEWER water receives a grade of D (21/100), which is considered poor. 1 contaminant(s) exceed EPA legal limits and 53 violation(s) are on record. Customers may want to consider using a water filter.
What contaminants has SAMMAMISH PLATEAU WATER & SEWER detected?
77 contaminants were tested in SAMMAMISH PLATEAU WATER & SEWER's water. Notable contaminants include Copper (90th percentile), Lead (90th percentile), chlorate. 1 exceed EPA legal limits (MCLs). 3 exceed EPA health goals (MCLGs).
Does SAMMAMISH PLATEAU WATER & SEWER have any EPA violations?
Yes, SAMMAMISH PLATEAU WATER & SEWER has 53 EPA violation(s) on record, with the most recent in 2009. Violation types include MR, MCL. 3 are health-based violations.
How many people does SAMMAMISH PLATEAU WATER & SEWER serve?
SAMMAMISH PLATEAU WATER & SEWER serves approximately 79,362 people, Washington.
What type of water does SAMMAMISH PLATEAU WATER & SEWER provide?
SAMMAMISH PLATEAU WATER & SEWER sources its water from purchased surface water. Surface water comes from rivers, lakes, or reservoirs and typically requires more extensive treatment. The utility's system ID is WA5340900.
How does SAMMAMISH PLATEAU WATER & SEWER compare to other utilities in Washington?
SAMMAMISH PLATEAU WATER & SEWER scores 21/100 with a grade of D (poor). This score suggests significant water quality concerns relative to other utilities. Visit our Washington state page for a full comparison of water systems.