Current through Reg. 49, No. 12; March 22, 2024
(a)
General standards attainment sampling and assessment procedures. The procedures
listed in this section are solely for the purposes of assessing water quality
monitoring data to determine if water quality standards are attained in
individual water bodies. Unless otherwise stated in this chapter, additional
details concerning sampling procedures for the measurement, collection,
preservation and laboratory analysis of water quality samples are provided in
the Texas Commission on Environmental Quality (TCEQ) Surface Water
Quality Monitoring Procedures, Volume 1: Physical and Chemical Monitoring
Methods (RG-415) as amended, the most recently published edition of
the book entitled Standard Methods for the Examination of Water and
Wastewater, 40 Code of Federal Regulations (CFR) Part 136, or other
reliable sources acceptable to the commission. Laboratory accreditation
requirements are specified in Chapter 25 of this title (relating to
Environmental Testing Laboratory Accreditation and Certification). Unless
otherwise stated in this chapter, additional details concerning how sampling
data are evaluated to assess standards compliance are provided in the TCEQ
Guidance for Assessing and Reporting Surface Water Quality in
Texas as amended.
(b)
Samples to determine standards attainment are collected at locations approved
by the commission. Samples collected at non-approved locations may be accepted
at the discretion of the commission. Samples to determine standards attainment
in ambient water must be representative in terms of location, seasonal
variations, and hydrologic conditions. Locations must be typical of significant
areas of a water body. Temporal sampling must be sufficient to appropriately
address seasonal variations of concern. Sample results that are used to assess
standards attainment must not include samples that are collected during extreme
hydrologic conditions such as high-flows and flooding immediately after heavy
rains. Further guidance on representative sampling, both spatially, temporally,
and hydrologically, can be found in the TCEQ Surface Water Quality
Monitoring Procedures, Volume 1: Physical and Chemical Monitoring
Methods (RG-415), Surface Water Quality Monitoring Procedures,
Volume 2: Methods for Collecting and Analyzing Biological Assemblage and
Habitat (RG-416), and the TCEQ Guidance for Assessing and
Reporting Surface Water Quality in Texas as amended.
(c) Collection and preservation of water
samples.
(1) For the purposes of assessing
standards attainment, samples are collected and preserved in accordance with
procedures set forth in the most recently published edition of the book
entitled Standard Methods for the Examination of Water and
Wastewater, the TCEQ Surface Water Quality Monitoring
Procedures, Volume 1: Physical and Chemical Monitoring Methods
(RG-415) as amended, 40 CFR Part 136, or other reliable procedures acceptable
to the commission.
(2) Bacterial
and temperature determinations must be conducted on samples or measurements
taken at or near the surface in accordance with the TCEQ Surface Water
Quality Monitoring Procedures, Volume 1: Physical and Chemical Monitoring
Methods (RG-415) as amended. Depth collection procedures for chloride,
sulfate, total dissolved solids, dissolved oxygen, chlorophyll
a, and pH to determine standards attainment may vary depending
on the water body being sampled. Standards for chloride, sulfate, total
dissolved solids, dissolved oxygen, chlorophyll a, pH are
applicable to the mixed surface layer, but a single sample taken near the
surface normally provides an adequate representation of these parameters. When
the water column is entirely mixed according to determinations described in
TCEQ Guidance for Assessing and Reporting Surface Water Quality in
Texas as amended, standards may apply to any sample taken in the water
column for parameters indicated in this section.
(3) For toxic materials, numerical aquatic
life criteria are applicable to water samples collected at any depth. Numerical
human health criteria are applicable to the average (arithmetic) concentration
from the surface to the bottom. For the purposes of standards attainment for
aquatic life protection and human health protection, samples that are collected
at approximately one foot below the water surface are acceptable for assessing
standards attainment of numerical criteria.
(d) Sample analysis.
(1) Numerical criteria. Procedures for
laboratory analysis must be in accordance with the most recently published
edition of the book entitled Standard Methods for the Examination of
Water and Wastewater, the TCEQ Surface Water Quality
Monitoring Procedures, Volume 1: Physical and Chemical Monitoring
Methods (RG-415) as amended, 40 CFR Part 136, or other reliable
procedures acceptable to the commission, and in accordance with Chapter 25 of
this title.
(2) Radioactivity.
Measurements must be made on filtered samples to determine radioactivity
associated with dissolved minerals in accordance with current analytical
methodology approved by the EPA.
(3) Toxicity. Bioassay techniques must be
selected as testing situations dictate but are generally conducted using
representative sensitive organisms in accordance with §
307.6
of this title (relating to Toxic Materials).
(e) Sampling periodicity and evaluation.
(1) Chloride, sulfate, total dissolved
solids. Standards attainment determinations to demonstrate compliance with the
annual average may be based on the long term mean in accordance with TCEQ
Guidance for Assessing and Reporting Surface Water Quality in
Texas as amended. Results from all monitoring stations within the
segment are used to allow for reasonable parametric gradients. Total dissolved
solids determinations may be based on measurements of specific
conductance.
(2) Radioactivity. The
impact of radioactive sources on surface waters must be evaluated in accordance
with Chapter 336 of this title (relating to Radioactive Substance Rules), and
in accordance with Chapter 290 of this title (relating to Public Drinking
Water).
(3) Bacteria.
(A) For coastal recreation waters, as defined
in §
307.3
of this title (relating to Definitions and Abbreviations), standards attainment
must be based on a geometric mean or a single sample criterion. Data are
evaluated in accordance with §
307.7(b)(1)
of this title (relating to Site-Specific Uses and Criteria).
(B) For inland waters (tidal rivers, high
saline inland waters, and freshwater), and other non-coastal recreation waters,
standards attainment must be based on a long-term geometric mean of applicable
samples in accordance with the TCEQ's Guidance for Assessing and
Reporting Surface Water Quality in Texas as amended. Data are
evaluated in accordance with §
307.7(b)(1)
of this title.
(C) Samples may be
evaluated with the single sample criterion for the purposes of swimmer safety
notification programs and wastewater permit compliance.
(D) Determination of attainment may account
for statistical variability to reduce uncertainty in evaluations in accordance
with the TCEQ's Guidance for Assessing and Reporting Surface Water
Quality in Texas.
(4) Toxic materials. Standards attainment
must be evaluated in accordance with §
307.6
of this title, and in accordance with §
307.8 of
this title (relating to Application of Standards). To protect aquatic life,
specific numerical acute toxic criteria are applied as 24-hour averages, and
specific numerical chronic toxic criteria are applied as seven-day averages.
Human health criteria are applied as long-term average exposure criteria
designed to protect populations over a life time. Standards attainment for
acute and chronic toxic criteria for aquatic life and human health criteria
must be in accordance with the TCEQ Guidance for Assessing and
Reporting Surface Water Quality in Texas as amended. Standards
attainment for human health criteria must be based on the mean of samples
collected in accordance with the TCEQ Guidance for Assessing and
Reporting Surface Water Quality in Texas as amended.
(5) Temperature and pH. Standards attainment
must be in accordance with the TCEQ Guidance for Assessing and
Reporting Surface Water Quality in Texas as amended.
(6) Dissolved oxygen.
(A) Criteria for daily (24-hour) average
concentrations must be compared to a time-weighted average of measurements
taken over a 24-hour period in accordance with TCEQ Guidance for
Assessing and Reporting Surface Water Quality in Texas as
amended.
(B) Criteria for minimum
concentrations must be compared to individual measurements in accordance with
TCEQ Guidance for Assessing and Reporting Surface Water Quality in
Texas as amended. When data are collected over a 24-hour period, the
lowest measurement observed during that 24-hour period is compared to the
applicable minimum criterion.
(7) Assessment of chlorophyll
a criteria in reservoirs. Procedures to determine standards
attainment for chlorophyll a criteria in reservoirs must be in
accordance with the TCEQ Guidance for Assessing and Reporting Surface
Water Quality in Texas as amended, including the evaluation of
multiple uses as indicated in §
307.7(b)(4)
of this title. Chlorophyll a criteria in individual reservoirs
are found in Appendix F of §
307.10 of this
title (relating to Appendices A - G). The data for the assessment must be
collected at the sampling stations used for calculating the criteria, as listed
in Appendix F of §
307.10 of this
title, or from comparable stations in the main pool of the reservoir.
Assessment values indicated in the TCEQ Guidance for Assessing and
Reporting Surface Water Quality in Texas are to be used for assessment
purposes only and are not to be used as water quality-based effluent limits in
wastewater discharge permits for wastewater permitting.
(8) Site-specific criteria for aquatic
recreation (geometric mean), total dissolved solids, chloride, and sulfate as
established in Appendix A of §
307.10 of this
title, and human health criteria as established in Table 2 of §
307.6(d)(1)
of this title do not apply in the following stream types and flow conditions:
(A) perennial streams when flows are below
0.1 cubic feet per second;
(B)
intermittent streams when less than 20% of the stream bed of a 500 meter
sampling reach is covered by pools; or when extremely dry conditions are
indicated by comparable observations of flow severity.
(f) Biological integrity.
Biological integrity, which is an essential component of the aquatic life
categories defined in §
307.7(b)(3)
of this title, is assessed by sampling the aquatic community. Attainment of
biological integrity is assessed by indices of biotic integrity that are
described in the TCEQ Surface Water Quality Monitoring Procedures,
Volume 2: Methods for Collecting and Analyzing Biological Assemblage and
Habitat Data (RG-416) as amended. Determination of attainment may
account for statistical variability to reduce uncertainty in evaluations in
accordance with TCEQ Guidance for Assessing and Reporting Surface Water
Quality in Texas as amended. Primary criteria associated with
assessing the attainment of aquatic life uses are indices of biotic integrity
and criteria for dissolved oxygen. When the appropriate aquatic life use as
determined by the use-attainability study is less stringent than the presumed
high use, then the appropriate aquatic life use and dissolved oxygen criteria
are listed in Appendix D of §
307.10 of this
title after approval by EPA.
(g)
Additional parameters. Assessment of narrative criteria parameters must be
performed in accordance with the TCEQ Guidance for Assessing and
Reporting Surface Water Quality in Texas as amended.
