Standard Interpretation
Standard: NEFAP
Section: 3.1
Link to relevant standard
REQUEST:
Does Environmental Sampling include sampling at water and wastewater plants?
TNI FINAL RESPONSE:
3.1 Environmental Sampling: Equivalent to "Field Sampling." See Clause 3.5.
3.2 Field: Any location outside the controlled environment of a laboratory.
3.5 Field Sampling: The process of obtaining a representative portion of an environmental matrix suitable for laboratory or field measurement or analysis.
In the definitions of the terms "Environmental Sampling" (3.1) and "Field Sampling", the operative term is "Field". In Clause 3.2 "Field" is defined as distinct from the "controlled" laboratory environment. It follows that the sampling sites for waste and drinking water treatment plants would be outside of a controlled environment so the answer to the question is "yes".
If the FSMO seeks accreditation to the TNI FSMO Volume 1 standard then the requirements in this standard apply.

develop consensus standards for use by TNI's programs. This group has a support role in assisting other programs with activities such as guidance and standards interpretation.
fosters the generation of data of known and documented quality is through the National Environmental Laboratory Accreditation Program, or NELAP. The purpose of this program is to establish and implement a program for the accreditation of environmental laboratories.
is to establish and maintain a national PT program to support TNI’s National Environmental Laboratory Accreditation Program, and other activities.
Field Activities Program (NEFAP) Executive Committee is to establish and implement an accreditation program for field sampling and measurement organizations (FSMOs).
Audit Sample Program is to develop consensus standards for the manufacture and analysis of audit samples for source emission testing.
on a variety of topics of interest to the environmental measurement community. TNI also hosts two regularly scheduled meetings per year, typically in January and August. Both are a week long and involve open meetings of TNI committees as well as training courses and other special sessions.