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Environmental Laboratory (NELAP) Accreditation

This page offers information on the Agency's National Environmental Laboratory Accreditation Program (NELAP)

Laboratories are assessed against the provisions of the 2009 TNI NELAP standards. 




The TCEQ Lab Accreditation Program is issuing a revision to the drinking water fields of accreditation for microbiology.  The fields have been revised to provide more clarity for the accredited laboratory, to include E. coli as an analyte in addition to total coliforms for presence/absence analyses, and to reflect the Revised Total Coliform Rule (40 CFR 141.851) which went into effect on April 1, 2016.  The changes to the drinking water fields of accreditation for microbiology will be effective October 15, 2016.

Currently accredited laboratories will receive a revised scope on October 15, 2016. The renewal date for a laboratory’s accreditation will not change.  No action is required for currently accredited laboratories.

Beginning October 15, 2016, a laboratory submitting an application for accreditation or those seeking amended fields to a current accreditation, will submit the revised field of accreditation checklist with their application.

Additional detailed information  (PDF)

New Fields Summary  (PDF)


On May 1, 2016, SM 4500-CN¯ F was added to the Drinking Water Fields of Accreditation.  The analyte offered for this method is Free cyanide.  From this date on, laboratories submitting free cyanide data by this method need to be accredited or risk having their data refused by the TCEQ.

The analyte, Free cyanide, is not listed on the TNI Fields of Proficiency Testing Table; therefore, there is no requirement in the TNI Standard to analyze two Proficiency Testing (PT) samples per year.  However, 40 Code of Federal Regulations (CFR), Part 141.23.k.3 requires any laboratory analyzing for free cyanide in drinking water by SM 4500-CN¯ F to achieve quantitative results within defined acceptance limits on one PT sample per year.  The TCEQ has determined that, due to the composition of the PT sample, a laboratory can analyze the total cyanide PT sample from the TNI FoPT table using SM 4500-CN¯ F to meet the requirement in 40 CFR.  The results from the analysis using SM 4500-CN¯ F should not be submitted to the TCEQ.

There is no change in the accreditation or PT requirements for laboratories analyzing total cyanide by SM 4500-CN¯ C,E and SM 4500-CN¯ E.



Subscribe to NELAC e-mail updates 

Go to this link: Get e-mail updates on your choice of topics.

After entering your e-mail address and personal preferences, mark the Laboratory Accreditation / Environmental Laboratory (NELAC) Accreditation box.


Application, Fields of Accreditation, Checklists, and Procedures

Application (PDF) (Revision 7 - August 2012)

Current Fields of Accreditation (FoAs)  (PDF) (Revision 16 - May 2016)

Future Fields of Accreditation (FoAs)  (PDF) (Revision 17 - October 2016)


History of changes to the Fields of Accreditation (PDF)


The current list of accredited laboratories, with links to their scope of accreditation, can be accessed here:

List of Accredited Laboratories (PDF)


The accreditation team uses the 2009 TNI Quality Systems checklist  Exit the TCEQ to determine each laboratory's conformance to the elements of this Standard.  A copy of the TNI checklist is now available directly from their web page.

Be advised that you must have a copy of the TNI Standard ELV1, Management and Technical Requirements for Laboratories Performing Environmental Analyses before you may download this checklist.


TCEQ (Internal) Accreditation Procedures (PDF)


Accreditation applications in progress (PDF)


For administrative information, please contact our records specialist at 512/239-3754 or e-mail us at


For additional information, including suitable ways to obtain traceability of measurements, or to make a complaint, please contact the program manager at 512/239-1990 or e-mail us at


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Frequently Asked Questions (FAQs)

This is a document addressing frequently asked questions regarding the Texas laboratory accreditation program:

FAQ guides (PDF)


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External Links


The NELAC Institute (TNI)  Exit the TCEQ


National Environmental Laboratory Accreditation Program (NELAP) designated proficiency testing providers  Exit the TCEQ


NELAP Fields of Proficiency Testing  Exit the TCEQ


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Our mailing address is:

Texas Laboratory Accreditation Program
Texas Commission on Environmental Quality
P.O. Box 13087, MC-165
Austin, TX 78711-3087


Our physical address for overnight mail delivery is:

Texas Laboratory Accreditation Program
Texas Commission on Environmental Quality
12100 Park 35 Circle, Bldg B, MC-165
Austin, TX 78753



Rules (Including Fees) and Accreditation Standards



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