City of Grand Coulee Water Dept
What EPA’s and Washington’s records show in this utility’s water: nitrate, arsenic and other regulated chemicals; lead and copper; and violations since 2016, with the certification that handles each result.
- Serves
- 1,428 people
- Connections
- 662
- Water source
- Groundwater bought from another system
- Based in
- Grand Coulee, WA
- County
- Grant
- Owner
- Local government
The ZIP code it serves
The short answer
Nothing in EPA’s and Washington’s records for this utility is above a health goal. That covers nitrate, arsenic and other regulated chemicals, plus lead and copper, not everything. No health-based violations on file since 2016.
What was found
Total trihalomethanes (TTHM) and haloacetic acids (HAA5): Washington’s own results, samples taken from July 21, 2020 to Aug. 19, 2026, with EPA’s 2012 to 2019 file for earlier years.
Below EPA’s limits2
Total trihalomethanes (TTHM)
Forms or is added in treatment
16.2ppb
Highest yearly average, 2020 to 2026
Averaged by year, the highest was 16.2 ppb, in 2026, below EPA’s legal limit of 80 ppb. That was also the latest year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 20.3 ppb, in 2012.
What handles it
- NSF/ANSI 53 look for “Trihalomethanes (TTHM) Reduction”
- NSF/ANSI 58 look for “Trihalomethanes (TTHM) Reduction”
Haloacetic acids (HAA5)
Forms or is added in treatment
2.3ppb
Highest yearly average, 2020 to 2026
2026, one sample: 1.1 ppb
Averaged by year, the highest was 2.3 ppb, in 2023, below EPA’s legal limit of 60 ppb. In 2026, the latest year on file, its one sample was 1.1 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 3.1 ppb, in 2014.
What handles it
No certification claim covers this compound yet.
One compound tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
- Lead
Violations since 2016
No health-based violations on file with EPA since 2016.
What this report can’t tell you
Everything else. Total trihalomethanes (TTHM) and haloacetic acids (HAA5) results here are Washington’s own from 2020 on, with EPA’s national file for 2012 to 2019. City of Grand Coulee Water Dept’s own annual report, which it must send you every year, has the contaminants this page does not show.
Your own plumbing. Lead results are the 90th percentile across homes the utility samples. Your home’s service line, solder and fixtures decide yours. A certified lab test is the only way to know.
What it means for your health. This page reports what the records show and EPA’s limits and goals; it is not medical advice. If you are worried about a health effect, talk to a doctor or your local health department.
Anything after the latest data. SDWIS data is from 2026 Q3; UCMR 5 didn’t sample this utility; Washington’s results run from July 21, 2020 to Aug. 19, 2026.
Testing your own tap
The 3 labs Washington certifies closest to the area City of Grand Coulee Water Dept serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.
Okanogan County Public Health Laboratory
Okanogan, WA · about 32 miles
Certified for bacteria, nitrate
Lincoln County Environmental Health Lab
Davenport, WA · about 45 miles
Certified for bacteria
Soiltest Farm Consultants, Inc. Laboratory
Moses Lake, WA · about 61 miles
Certified for nitrate, minerals and other inorganics
Sources
- EPA UCMR 5 occurrence data, file of Oct. 15, 2026
- EPA SDWA bulk download (SDWIS federal data), 2026 Q3
- Washington State Department of Health, Office of Drinking Water, results from Jan. 1, 2020 to Sept. 29, 2026, read Oct. 8, 2026
- EPA Six-Year Review 4 compliance monitoring data, 2012 to 2019, file of Feb. 5, 2024
- Certified labs: Washington State Department of Ecology, Lab Accreditation Program, environmental laboratories accredited for drinking water analyses, read Oct. 10, 2026; distances from the Census 2020 ZIP code tabulation area gazetteer
- Limits and goals: each contaminant’s page, with its EPA source.
- How this page is built: methodology.
PWSID WA5328700. Rebuilt from EPA data on Oct. 18, 2026.
What to do next
- Nothing here is above a health goalIn EPA’s and Washington’s records for this utility. They don’t cover everything, which is why the next step matters.Every contaminant TapBuff tracks
- Get the utility’s own reportCity of Grand Coulee Water Dept must send you a water quality report every year. It covers contaminants this page does not show.How to read it
- Test your own tap for leadYour service line, solder and fixtures decide the lead at your faucet, not the utility’s average.Lead in your water: what to do
- Decide if you want a filter at allA filter for taste or chlorine is a preference, not a need. The standards say what each kind can do.NSF/ANSI standards, decoded