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Coulee Dam 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
1,454 people
Connections
628
Water source
Surface water
Based in
Coulee Dam, WA
County
Okanogan
Owner
Local government
Hardness
Moderately hard
The ZIP code it serves

99116

The short answer

1 result is above the health goal. The worst: Lead, above the health goal. No health-based violations on file since 2016.

What handles it

What was found

Lead and copper: EPA SDWIS monitoring periods ending 2004 to 2023.

Total trihalomethanes (TTHM), haloacetic acids (HAA5), nitrate, arsenic, chromium (total) and fluoride: Washington’s own results, samples taken from Feb. 11, 2020 to July 14, 2026, with EPA’s 2012 to 2019 file for earlier years.

Above the health goal1

Lead

Comes from pipes, often your own

Above the health goal

1.7ppb

90th percentile, 2021 to 2023

In the latest period, 9 in 10 homes sampled were at or below 1.7 ppb, below EPA’s action level of 15 ppb. The action level drops to 10 ppb on Nov. 1, 2027. EPA’s health goal for lead is zero.

What handles it

Below EPA’s limits3

Total trihalomethanes (TTHM)

Forms or is added in treatment

Below EPA’s limits

39.5ppb

Highest yearly average, 2020 to 2026

2026, one sample: 29.3 ppb

Averaged by year, the highest was 39.5 ppb, in 2023, below EPA’s legal limit of 80 ppb. In 2026, the latest year on file, its one sample was 29.3 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 43.3 ppb, in 2017.

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

Below EPA’s limits

22ppb

Highest yearly average, 2020 to 2026

2026, one sample: 18.8 ppb

Averaged by year, the highest was 22 ppb, in 2023, below EPA’s legal limit of 60 ppb. In 2026, the latest year on file, its one sample was 18.8 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 22.1 ppb, in 2017.

What handles it

No certification claim covers this compound yet.

Nitrate

Comes from the source

Below EPA’s limits

0.18ppm

Highest sample; found in 8 of 9

2025, one sample: 0.18 ppm

The highest sample, in 2025, was 0.18 ppm, below EPA’s legal limit of 10 ppm. That was also the latest year on file, and its one sample was 0.18 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 0.24 ppm, in 2019.

What handles it

  • NSF/ANSI 58 look for “Nitrate/Nitrite Reduction”
  • NSF/ANSI 53 look for “Nitrate/Nitrite (30 ppm challenge)”
3 compounds tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
  • Arsenic
  • Chromium (total)
  • Fluoride

What handles it

A certification covers specific claims, not a whole standard. Look for these claims on the certifier’s listing, not the box. Wording varies a little: NSF writes “Lead Reduction,” WQA just “Lead.”

At the tap, or for the whole house?

Lead and copper usually come from pipes and fixtures inside or near your home. A whole-house system sits where water enters, so it cannot catch what your own plumbing adds after it. For those, the filter that counts is the one at the tap. How whole-house systems compare.

Filters with those claims on a certifier’s listing

Disclosure: TapBuff earns a commission if you buy through some links on this page. It does not change which standard or filter we name. As an Amazon Associate, TapBuff earns from qualifying purchases. How TapBuff makes money

Compare five-year costs

The best water filters for lead, ranked

Hardness

Moderately hard, 60 mg/L (3.5 grains per gallon), at its one sampling point, in 2020.

Hardness is calcium and magnesium. EPA sets no limit for it: it shows up as scale on fixtures and in water heaters, and as soap that won’t lather. USGS calls water above 60 mg/L moderately hard, above 120 hard and above 180 very hard.

Softeners compared at 3.5 grains per gallon, salt includedSoftener or salt-free conditioner?Washington water hardness, utility by utility

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), haloacetic acids (HAA5), nitrate, arsenic, chromium (total) and fluoride results here are Washington’s own from 2020 on, with EPA’s national file for 2012 to 2019. Coulee Dam 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 Feb. 11, 2020 to July 14, 2026.

Testing your own tap

Coulee Dam Water Dept’s results are for the water it sends out. What your own service line, solder and fixtures add shows up only in a test of your tap, by a lab Washington certifies.

The 3 labs Washington certifies closest to the area Coulee Dam 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 36 miles

    Certified for bacteria, nitrate

    (509) 422-7140

  • Lincoln County Environmental Health Lab

    Davenport, WA · about 41 miles

    Certified for bacteria

    (509) 215-1034

  • Soiltest Farm Consultants, Inc. Laboratory

    Moses Lake, WA · about 63 miles

    Certified for nitrate, minerals and other inorganics

    (509) 765-1622

All 84 certified labs for Washington

Sources

PWSID WA5315400. Rebuilt from EPA data on Oct. 18, 2026.

Also in Okanogan County

All Washington utilities

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