Illinois EPA
Illinois environmental lab accreditation, IL ELAP and NELAP.
Which Illinois labs must be accredited, which standard applies, how out-of-state labs qualify, and the calibration findings Illinois EPA keeps writing up.
At a glance
How environmental lab accreditation works in Illinois.
Illinois EPA’s Division of Laboratories runs the Environmental Laboratory Accreditation Program. It has been a NELAP accrediting authority since July 1, 1999, and it accredits chemistry only.
NELAP accreditation body
- Program
- Environmental Laboratory Accreditation Program (IL ELAP), Quality Assurance Section, Division of Laboratories, Illinois EPA
- Legal basis
- 35 Illinois Administrative Code Part 186 (accreditation) and Part 185 (fees), under 415 ILCS 5/4
- Standard
- TNI EL-V1-2016-Rev 2.1 and EL-V2-2016-Rev 2.0, incorporated in 35 Ill. Adm. Code 186.115. The older Part 186 sections on calibration and QA have been repealed in favor of the TNI standard.
- Who needs it
- Labs submitting community water supply compliance data to the Illinois EPA Bureau of Water. Some Bureau of Land programs also require Part 186 accreditation; for example, LUST samples collected on or after January 1, 2003 must be analyzed by an accredited lab (35 Ill. Adm. Code 734.420). Other accreditation is voluntary.
- Scope
- Drinking water, wastewater and hazardous waste, for inorganic and organic chemistry only
- Microbiology
- The Illinois Department of Public Health separately certifies drinking water microbiology labs under 77 Ill. Adm. Code 465, with on-site re-evaluation every two years. That program is not NELAP.
- Out-of-state labs
- Secondary accreditation requires evidence of primary accreditation from a NELAP accreditation body (186.125). Illinois EPA placed a moratorium on primary accreditation of out-of-state labs on August 1, 2011. Its pages do not say whether the moratorium has been lifted, so confirm with the agency.
The accreditation cycle
The Illinois accreditation cycle.
Illinois follows the TNI standard for assessment and PT intervals rather than setting its own in the rule.
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Apply by method
Apply for the drinking water, wastewater or hazardous waste methods your lab reports.
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New methods
Before an on-site assessment for a new method, Illinois EPA asks for the SOP, MDLs, analyst DOCs, example data and two passing PT results at least seven days apart (Lab Communication, July 2026).
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One-year accreditation
Accreditation is valid for one year and may be renewed annually (186.125).
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Assessment and PT
On-site assessment and ongoing PT follow the 2016 TNI standard.
Initial calibration
What auditors check in your initial calibrations.
Illinois EPA publishes regular lab communications that list the nonconformities its assessors find most often. Calibration features in them repeatedly.
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.
Enough points, and no reporting above the top
A common Illinois finding is too few calibration levels: “5 points for linear and 6 points for quadratic, not counting zero as a point.” And no reporting above your highest calibration level.
Source: Illinois EPA Lab Communication, April 2026
The same communication notes that a standard at least 10 percent above the highest calibration point must be run on a defined schedule, and that the TNI requirement on measurement traceability sits in Volume 1, Module 2, section 5.6.
Self-check
Are your initial calibrations ready for an Illinois 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.
Illinois specifics
Assessors are telling labs where the findings are.
Illinois EPA’s lab communications are unusually direct. They list the nonconformities assessors keep finding, and initial calibration is a regular entry: curves built on too few levels, quadratic fits without the sixth point, and results reported above the highest standard because a linear dynamic range study seemed to allow it.
Each of those is a modeling decision. Choosing a quadratic fit commits the lab to more standards, and choosing a range commits it to what it can report. Making that choice consistently, and recording why, is what keeps a lab off the next list.
The program is also growing. Standard Methods 24th Edition is now accreditable, harmful algal bloom toxin analyses have been added, and Illinois enacted the Safe Public Drinking Water Act (Public Act 103-1077) in March 2025, which requires a state-only MCL for 1,4-dioxane by June 30, 2030.
How WLTR helps
Calibration evidence ready for an Illinois EPA assessment.
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 Illinois EPA assessor.
See every candidate model for your curves, with the point counts and range each one needs, before an assessor counts them.
Questions
Illinois accreditation FAQs
Is Illinois a NELAP state?
Yes. Illinois EPA has been a NELAP accrediting authority since July 1, 1999, and accredits labs to the 2016 TNI standard.
Which Illinois labs must be accredited?
Labs submitting community water supply compliance data to the Illinois EPA Bureau of Water. Some Bureau of Land programs also require it, such as LUST sample analysis under 35 Ill. Adm. Code 734.420. Other accreditation is voluntary.
How many calibration points does Illinois EPA expect?
Illinois EPA lab communications cite five points for a linear calibration and six for a quadratic, not counting zero as a point.
Can a lab report results above its highest calibration standard?
Not in Illinois. Illinois EPA states that even with an established linear dynamic range, no reporting above the highest calibration level is permitted.
Who certifies drinking water microbiology labs in Illinois?
The Illinois Department of Public Health, under 77 Ill. Adm. Code 465. Illinois EPA accredits chemistry only.
Sources
Primary sources for this page.
- Illinois EPA, Environmental Laboratory Accreditation (opens in a new tab)
- Illinois EPA, lab accreditation FAQs (opens in a new tab)
- 35 Ill. Adm. Code Part 186 (opens in a new tab)
- Illinois EPA Lab Communication, April 2026 (opens in a new tab)
- Illinois EPA Lab Communication, July 2026 (opens in a new tab)
- Illinois EPA, lab accreditation updates and lab communications (opens in a new tab)
- 35 Ill. Adm. Code 734.420, LUST laboratory requirements (opens in a new tab)
- IDPH, environmental 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 Illinois Environmental Protection Agency. Spot something out of date? Tell us at admin@wltr.tech.
Before your next assessment
See your Illinois ICALs the way an assessor 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
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