Washington Department of Ecology
Washington environmental lab accreditation, WA ELAP and Chapter 173-50 WAC.
Who accredits your lab in Washington, how drinking water labs fit in, why accreditation elsewhere does not carry over automatically, and the calibration rules written into the code.
At a glance
How environmental lab accreditation works in Washington.
Washington is not a NELAP state. The Department of Ecology runs one accreditation program under its own rule, and that program also accredits the labs that report drinking water data to the Department of Health.
State program (non-NELAP)
- Program
- Washington State Environmental Laboratory Accreditation Program (WA ELAP), Department of Ecology, which describes itself as the accrediting body in Washington state
- Rule
- Chapter 173-50 WAC, Accreditation of Environmental Laboratories. The quality control and proficiency testing sections were last amended effective October 2, 2023, and a 2026 rulemaking amended the fee section, 173-50-190, effective September 11, 2026.
- Who needs it
- Labs that conduct tests or prepare analytical data for submittal to Ecology, the Department of Health, or any other entity that requires an accredited lab (173-50-010 and 173-50-020). Accreditation alone does not authorize a method for a specific program or project.
- Drinking water
- Ecology accredits drinking water labs that report to the Department of Health’s Office of Drinking Water. DOH’s Lab Rule, chapter 246-390 WAC, requires those labs to be accredited under chapter 173-50 WAC.
- Matrices and categories
- Matrix groups include nonpotable water, drinking water, solid and chemical materials, and air and emissions. Categories are general chemistry, trace metals, organics I and II, microbiology, radiochemistry, bioassay, immunoassay and physical (173-50-120).
- NELAP status
- Not a NELAP accreditation body. Washington does not appear on TNI’s list of NELAP recognized accreditation bodies.
- Out-of-state and third-party
- Labs must apply whether or not they are already accredited in another state or country, and Ecology has no automatic reciprocity. It may recognize third-party accreditation it finds equivalent to its own process (173-50-170), which can streamline some steps.
The accreditation cycle
From application to renewal.
The steps below summarize Chapter 173-50 WAC and Ecology’s application and renewal pages. Your certificate, scope of accreditation and Ecology correspondence govern the specifics for your lab.
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Apply with your QA manual
Submit the application and your quality assurance manual, and have your PT provider send results directly to Ecology. An on-site audit is required, by Ecology or an approved third party.
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Proficiency testing
At least two PT samples per applicable parameter per year, or one for bioassay parameters. After two satisfactory results and none unsatisfactory in an accreditation year, one satisfactory result per year is enough until an unsatisfactory result intervenes (173-50-070).
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Triennial audits
Directly accredited labs are audited on a triennial basis (173-50-080). For drinking water parameters, on-site audits may not be more than three years apart (173-50-130).
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Annual renewal
Accreditation is granted for one year and expires one year after its effective date (173-50-130). The renewal application opens in Ecology’s online portal six weeks before the certificate expires.
Initial calibration
What auditors check in your initial calibrations.
Washington writes calibration requirements into its own rule. WAC 173-50-061 sets limits on how a multilevel curve is built and checked, on top of what each method requires.
A range that brackets what you report
The lowest standard should sit at or below your reporting limit and the highest at or above the top concentration you report. Results outside the calibrated range need to be qualified.
Error at the low end, not r² alone
A correlation coefficient of 0.999 can still hide a low standard that back-calculates 30 percent off. Auditors look at relative error, especially at the lowest levels.
Records that rebuild the curve
Raw responses, the model and weighting used, any excluded points with the reason, and the verification that followed. An auditor should be able to reconstruct every initial calibration from the record.
Every point kept and recalculated
WAC 173-50-061 bars removing midpoints from a multilevel curve, except consecutive points at either end or a documented error with an identified cause, and that point is then excluded for every analyte. Each point is recalculated against the curve and must meet the method’s calibration verification limits, or 50 to 150 percent at or below the LOQ, unless the method specifies otherwise.
Source: WAC 173-50-061
The same section requires a standard at the limit of quantitation at least annually, recovering 50 to 150 percent of the true value, for listed technologies including chromatography, ICP, ion chromatography and mass spectrometry when the method sets no LOQ requirement. WAC 173-50-069 also requires that final sample results can be recreated from records.
Self-check
Are your initial calibrations ready for a Washington assessment?
Tick what your lab could show an auditor today. Nothing you select is saved or sent anywhere.
6Checks to work through
Select each item your lab could show an auditor today.
A self-assessment to help you prepare, not a compliance determination.
Washington specifics
Accreditation elsewhere is not a Washington certificate.
Labs accredited by another state or a third party still apply to Ecology. Ecology states it has no automatic reciprocity. It may recognize third-party accreditation it determines to be equivalent to Chapter 173-50 WAC, and for those labs it reviews a recent audit from the primary accrediting authority, but the lab is accredited to Washington’s rule.
That rule is specific about calibration. Since October 2, 2023, WAC 173-50-061 has limited which points may be dropped from a multilevel curve, required every point to be recalculated against the curve, and set a 50 to 150 percent limit for points at or below the LOQ. An auditor compares your records to that section, not only to the method.
The rules continue to change. Ecology adopted a rulemaking on August 11, 2026, effective September 11, 2026, that amended the fee section of Chapter 173-50 WAC, and the Department of Health amended its drinking water Lab Rule, chapter 246-390 WAC, effective July 18, 2025. Status is as of October 2026.
How WLTR helps
Calibration evidence ready for a Washington audit.
WLTR independently reviews the calibration your instrument software produced. Your analyst still makes the final call. What changes is that the evidence is complete, consistent across analysts, and ready before the auditor asks for it.
- Each analyte reviewed one at a time in the instrument software.
- The model and weighting are whatever the batch was processed with.
- r² is the number most people look at, even though it does not measure error at the low end.
- QA signs off without an independent check on the curve.
- Every analyte and every candidate model side by side in the Calibration Intelligence dashboard.
- Diagnostics run automatically and the best fit curve is identified, with the reasons recorded.
- Relative error at every level, including the lowest standard, shown on one screen.
- A traceable record your QA manager can review, sign and hand to an Ecology auditor.
See how your own ICAL data looks when every analyte and model is laid out for review.
Questions
Washington accreditation FAQs
Is Washington a NELAP state?
No. The Department of Ecology is not a NELAP accreditation body, and Washington does not appear on TNI’s list of NELAP recognized accreditation bodies.
Who accredits drinking water labs in Washington?
The Department of Ecology. It accredits drinking water labs that report to the Department of Health’s Office of Drinking Water, and DOH’s Lab Rule, chapter 246-390 WAC, requires accreditation under chapter 173-50 WAC.
Does Washington accept accreditation from other states?
Not automatically. Labs must apply to Ecology whether or not they are accredited elsewhere. Ecology may recognize third-party accreditation it determines to be equivalent (WAC 173-50-170), which can streamline parts of the process.
How often are Washington labs audited and tested?
Directly accredited labs are audited on a triennial basis, and drinking water on-site audits may not be more than three years apart. Labs analyze at least two PT samples per applicable parameter per year (one for bioassay), dropping to one after two satisfactory results with none unsatisfactory.
Does Washington have its own calibration rule?
Yes. WAC 173-50-061 limits removal of calibration points, requires each point to be recalculated against the curve and meet method verification limits, and requires an annual LOQ standard for listed technologies when the method sets no LOQ requirement.
Sources
Primary sources for this page.
- Ecology, environmental lab accreditation (opens in a new tab)
- Ecology, first-time applications (opens in a new tab)
- Ecology, renewing accreditation (opens in a new tab)
- Ecology, laws, rules and methods (opens in a new tab)
- Chapter 173-50 WAC, Accreditation of Environmental Laboratories (opens in a new tab)
- WAC 173-50-061, required quality control practices (opens in a new tab)
- Ecology rulemaking, Chapters 173-455, 173-400 and 173-50 WAC (opens in a new tab)
- Chapter 246-390 WAC, drinking water laboratory certification (opens in a new tab)
This page summarizes public program information to help labs prepare. Requirements change, and the agency’s current rules and guidance always take precedence. WLTR is not affiliated with or endorsed by the Washington State Department of Ecology. Spot something out of date? Tell us at admin@wltr.tech.
Before your next assessment
See your Washington ICALs the way an auditor will.
Bring a recent initial calibration. We will walk you through every analyte and candidate model in the Calibration Intelligence dashboard, the best fit, and the record your QA manager would sign.
Request a demoHow the methodology works
Running environmental methods? See how WLTR works for environmental testing labs and water and wastewater utility labs.