Texas TCEQ
Texas environmental lab accreditation, TCEQ and NELAP.
Who must be accredited by TCEQ, how the NELAP cycle runs in Texas, how out-of-state labs qualify, and why your lowest calibration standard matters so much under TRRP.
At a glance
How environmental lab accreditation works in Texas.
The Texas Commission on Environmental Quality is one of the NELAP accreditation bodies. It accredits labs to the TNI standard and requires that accreditation for most environmental data used in commission decisions.
NELAP accreditation body
- Program
- Environmental laboratory accreditation, Texas Commission on Environmental Quality (TCEQ)
- Legal basis
- 30 Texas Administrative Code Chapter 25, Environmental Testing Laboratory Accreditation and Certification
- Standard
- The current NELAP standards (30 TAC 25.9). Since January 31, 2020, labs are assessed against the 2016 TNI standard.
- Who needs it
- Labs that provide data for TCEQ decisions on permits, compliance, enforcement or corrective action, including in-house labs whose data goes to third parties. For Safe Drinking Water Act data, TCEQ accreditation or EPA certification is accepted.
- Exceptions
- Listed in 30 TAC 25.6, including certain on-site or in-house labs inspected at least every three years, federally accredited labs, emergency response data, and data for which TCEQ offers no accreditation.
- Matrices
- Drinking water, non-potable water, air, solids and chemical materials, and biological tissue
- Out-of-state labs
- Secondary accreditation for labs accredited by another NELAP accreditation body, for fields already on their primary scope (30 TAC 25.22)
The accreditation cycle
The Texas accreditation cycle.
Texas certificates are short, so the cycle never really stops. The steps below come from 30 TAC Chapter 25.
-
Apply by field
List the matrix, method and analyte combinations your lab reports, and submit your quality system documentation.
-
One-year certificate
Accreditation is granted for one year and renewed annually (30 TAC 25.14).
-
Proficiency testing
At least two proficiency test samples per field of accreditation each year, where PT is available (30 TAC 25.20).
-
On-site assessment
At least every two years (30 TAC 25.18), against the 2016 TNI standard.
Initial calibration
What auditors check in your initial calibrations.
TCEQ assessors work from the TNI standard and your methods. For remediation data, TCEQ’s own data review guidance ties the initial calibration directly to what you can report.
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.
The lowest standard sets your limit
Under TCEQ’s TRRP data review guidance, the method quantitation limit is “the lowest non-zero concentration standard in the laboratory’s initial calibration curve.”
Source: TCEQ RG-366/TRRP-13, Review and Reporting of COC Concentration Data under TRRP
The same guidance asks reviewers whether every reported point fell between the lowest and highest standard used to build the curve. A weak low standard is not a cosmetic problem in Texas. It moves your quantitation limit.
Self-check
Are your initial calibrations ready for a Texas 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.
Texas specifics
Under TRRP, the initial calibration decides what you can report.
The Texas Risk Reduction Program uses laboratory data to decide whether a site is clean. TCEQ’s guidance for that data, RG-366/TRRP-13, defines the method quantitation limit as the lowest non-zero standard in the initial calibration. Detected results below it are reported as estimated values, and the data package has to show how the lab got there.
That puts the low end of the curve under a microscope. A model that fits the upper standards beautifully but misses the lowest standard by 25 percent is a model that weakens every low-level result in the report, and a data reviewer will see it on the checklist.
TCEQ continues to expand the program. New fields of accreditation took effect January 1, 2025, including PFAS by EPA Methods 533 and 537.1 for drinking water. In 2025 TCEQ proposed Rule Project 2025-016-025-AI, which would raise fees, add a PFAS fee category and repeal the Subchapter C certification rules. As of October 2026 the Texas Administrative Code did not yet reflect those changes. Check the TCEQ program page for current status.
How WLTR helps
Calibration evidence ready for a TCEQ assessment or a TRRP review.
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 a TCEQ assessor.
See how your lowest standards hold up across every candidate model, before a data reviewer does.
Questions
Texas accreditation FAQs
Is Texas a NELAP state?
Yes. TCEQ is a NELAP-recognized accreditation body and has assessed labs against the 2016 TNI standard since January 31, 2020.
Who needs TCEQ accreditation?
Labs that provide data for TCEQ decisions on permits, compliance, enforcement or corrective action, including in-house labs whose data goes to third parties. 30 TAC 25.6 lists the exceptions, and Safe Drinking Water Act data may come from a lab with EPA certification instead.
How long is a TCEQ accreditation valid?
One year. Labs renew annually, analyze at least two proficiency test samples per field each year where available, and receive an on-site assessment at least every two years.
Can a lab accredited in another NELAP state get Texas accreditation?
Yes, through secondary accreditation under 30 TAC 25.22, for the fields already on the lab’s primary NELAP scope.
How does the initial calibration affect TRRP reporting?
TCEQ’s TRRP data review guidance defines the method quantitation limit as the lowest non-zero standard in the initial calibration, so the accuracy of that standard directly affects what can be reported without qualification.
Sources
Primary sources for this page.
- TCEQ environmental laboratory accreditation (opens in a new tab)
- 30 TAC Chapter 25 (Texas Administrative Code, Cornell LII copy) (opens in a new tab)
- TCEQ Laboratory Accreditation Procedures (opens in a new tab)
- TCEQ RG-366/TRRP-13, Review and Reporting of COC Concentration Data (opens in a new tab)
- TNI list of NELAP accreditation bodies (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 Texas Commission on Environmental Quality. Spot something out of date? Tell us at admin@wltr.tech.
Before your next assessment
See your Texas ICALs the way a data reviewer will.
Bring a recent initial calibration. We will show you every analyte and candidate model side by side in the Calibration Intelligence dashboard, how the lowest standard holds up, 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.