| (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.
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