(a) Application. The general criteria set forth in
this section apply to surface water in the state and specifically
apply to substances attributed to waste discharges or human activities.
General criteria do not apply to those instances when surface water,
as a result of natural phenomena, exhibit characteristics beyond the
limits established by this section. General criteria are superseded
by specific exemptions stated in this section or in §307.8 of
this title (relating to the Application of Standards), or by site-specific
water quality standards for classified segments. Provisions of the
general criteria remain in effect in mixing zones or below critical
low-flow conditions unless specifically exempted in §307.8 of
this title.
(b) Aesthetic parameters.
  (1) Concentrations of taste and odor producing substances
must not interfere with the production of potable water by reasonable
water treatment methods, impart unpalatable flavor to food fish including
shellfish, result in offensive odors arising from the waters, or otherwise
interfere with the reasonable use of the water in the state.
  (2) Surface water must be essentially free of floating
debris and suspended solids that are conducive to producing adverse
responses in aquatic organisms or putrescible sludge deposits or sediment
layers that adversely affect benthic biota or any lawful uses.
  (3) Surface waters must be essentially free of settleable
solids conducive to changes in flow characteristics of stream channels
or the untimely filling of surface water in the state. This provision
does not prohibit dredge and fill activities that are permitted in
accordance with the Federal Clean Water Act.
  (4) Surface waters must be maintained in an aesthetically
attractive condition.
  (5) Waste discharges must not cause substantial and
persistent changes from ambient conditions of turbidity or color.

  (6) No foaming or frothing of a persistent nature is
permissible.
  (7) Surface waters must be maintained so that oil,
grease, or related residue do not produce a visible film or sheen
of oil or globules of grease on the surface or coat the banks or bottoms
of the watercourse; or cause toxicity to man, aquatic life, or terrestrial
life in accordance with subsection (d) of this section.
(c) Radiological substances. Radioactive materials
must not be discharged in excess of the amount regulated by Chapter
336 of this title (relating to Radioactive Substance Rules).
(d) Toxic substances. Surface waters must not be toxic
to man from ingestion of water, consumption of aquatic organisms,
or contact with the skin, or to terrestrial or aquatic life. Additional
requirements and criteria for toxic substances are specified in §307.6
of this title (relating to Toxic Materials). Criteria to protect aquatic
life from acute toxicity apply to all surface waters in the state
except as specified in §307.8(a)(3) of this title. Criteria to
protect aquatic life from chronic toxicity apply to surface waters
with an aquatic life use of limited, intermediate, high, or exceptional
as designated in §307.10 of this title (relating to Appendices
A - G) or as determined on a case-by-case basis in accordance with
subsection (l) of this section. Toxic criteria to protect human health
for consumption of fish apply to waters with a sustainable or incidental
fishery, as described in §307.6(d) of this title. Additional
criteria apply to water in the state with a public drinking water
supply use, as described in §307.6(d) of this title. The general
provisions of this subsection do not change specific provisions in §307.8
of this title for applying toxic criteria.
(e) Nutrients. Nutrients from permitted discharges
or other controllable sources must not cause excessive growth of aquatic
vegetation that impairs an existing, designated, presumed, or attainable
use. Site-specific nutrient criteria, nutrient permit limitations,
or separate rules to control nutrients in individual watersheds are
established where appropriate after notice and opportunity for public
participation and proper hearing. Site-specific numeric criteria related
to chlorophyll a are listed in Appendix
F of §307.10 of this title.
(f) Temperature. Consistent with §307.1 of this
title (relating to General Policy Statement) and in accordance with
state water rights permits, temperature in industrial cooling impoundments,
industrial cooling water areas, and all other surface water in the
state must be maintained so as to not interfere with the reasonable
use of such waters. Numerical temperature criteria have not been specifically
established for industrial cooling impoundments, which in most areas
of the state contribute to water conservation and water quality objectives.
In addition, numerical criteria for temperature are not applicable
in designated industrial cooling water areas, as defined in §307.3
of this title (relating to Definitions and Abbreviations). The horizontal
boundaries of an industrial cooling water area must be defined in
the applicable wastewater permit. The following temperature criteria,
expressed as a maximum temperature differential (rise over ambient)
are established except for industrial cooling impoundments, temperature
elevations due to discharges of treated domestic (sanitary) effluent,
and temperature elevations within designated mixing zones or industrial
cooling water areas. The maximum temperature differentials are:
  (1) freshwater streams: 5 degrees Fahrenheit (degrees
F);
  (2) freshwater lakes and impoundments: 3 degrees F;
and
  (3) tidal river reaches, bay, and gulf waters: 4 degrees
F in fall, winter, and spring, and 1.5 degrees F in summer (June,
July, and August).
  (4) Additional temperature criteria (expressed as maximum
temperatures) for classified segments are specified in Appendix A
of §307.10 of this title. These criteria are not applicable within
industrial cooling water areas.
(g) Salinity.
  (1) Concentrations and the relative ratios of dissolved
minerals such as chloride, sulfate, and total dissolved solids must
be maintained such that existing, designated, presumed, and attainable
uses are not impaired.
  (2) Criteria for chloride, sulfate, and total dissolved
solids for classified freshwater segments are specified in Appendix
A of §307.10 of this title.
  (3) Salinity gradients in estuaries must be maintained
to support attainable estuarine dependent aquatic life uses. Numerical
salinity criteria for Texas estuaries have not been established because
of the high natural variability of salinity in estuarine systems,
and because long-term studies by state agencies to assess estuarine
salinities are still ongoing. Absence of numerical criteria must not
preclude evaluations and regulatory actions based on estuarine salinity,
and careful consideration must be given to all activities that may
detrimentally affect salinity gradients.
(h) Aquatic life uses and dissolved oxygen.
  (1) Dissolved oxygen concentrations must be sufficient
to support existing, designated, presumed, and attainable aquatic
life uses. Aquatic-life use categories and corresponding dissolved
oxygen criteria are described in §307.7(b)(3) of this title (relating
to Site-Specific Uses and Criteria).
  (2) Aquatic life use categories and dissolved oxygen
criteria for classified segments are specified in Appendix A of §307.10
of this title. Aquatic life use categories and dissolved oxygen criteria
for other specific water bodies are specified in Appendix D of §307.10
of this title. Where justified by sufficient site-specific information,
dissolved oxygen criteria that differ from §307.7(b)(3) of this
title may be adopted for a particular water body in §307.10 of
this title.
  (3) Perennial streams, rivers, lakes, bays, estuaries,
and other appropriate perennial waters that are not specifically listed
in Appendix A or D of §307.10 of this title are presumed to have
a high aquatic life use and corresponding dissolved oxygen criteria.
Applicable dissolved oxygen criteria are described in §307.7(b)(3)(A)
of this title. Higher uses are protected where they are attainable.

  (4) When water is present in the streambed of intermittent
streams, a 24-hour dissolved oxygen mean of at least 2.0 mg/L and
24-hour minimum dissolved oxygen concentration of 1.5 mg/L must be
maintained. Intermittent streams that are not specifically listed
in Appendix A or D of §307.10 of this title are considered to
have a minimal aquatic life use except as indicated below in this
subsection. For intermittent streams with seasonal aquatic life uses,
dissolved oxygen concentrations commensurate with the aquatic life
uses must be maintained during the seasons when the aquatic life uses
occur. Unclassified intermittent streams with perennial pools are
presumed to have a limited aquatic life use and corresponding dissolved
oxygen criteria. Higher uses are protected where they are attainable.

(i) Aquatic life uses and habitat. Vegetative and physical
components of the aquatic environment must be maintained or mitigated
to protect aquatic life uses. Procedures to protect habitat in permits
for dredge and fill are specified in Federal Clean Water Act, §404
and in Chapter 279 of this title (relating to Water Quality Certification).

(j) Aquatic recreation.
  (1) Existing, designated, presumed, and attainable
uses of aquatic recreation must be maintained, as determined by criteria
that indicate the potential presence of pathogens. Categories of recreation
and applicable criteria are established in §307.7(b)(1) of this
title.
  (2) Recreational use categories and criteria for classified
segments are specified in Appendix A of §307.10 of this title.
Site-specific recreational use categories and criteria for selected
unclassified water bodies are specified in Appendix G of §307.10
of this title. Where justified by sufficient site-specific information,
recreational uses and criteria that differ from §307.7(b)(1)
of this title may be adopted for a particular water body in §307.10
of this title. For water bodies not specifically listed in Appendix
A or Appendix G of §307.10 of this title, the following recreational
uses are presumed to apply.
    (A) Primary contact recreation 1. Primary contact recreation
1 is presumed for lakes, reservoirs, and tidal water bodies. Primary
contact recreation 1 is presumed to apply to intermittent streams,
intermittent streams with perennial pools, nontidal wetlands, and
perennial freshwater streams and rivers, except where site-specific
information indicates that recreational activities that involve a
significant risk of ingestion have little to no likelihood of occurring,
in accordance with subparagraph (C) of this paragraph.
    (B) Primary contact recreation 2. No water body is
presumed to have a use of primary contact recreation 2. This use is
applicable when designated for an individual water body as listed
in Appendix A or G in §307.10 of this title. Primary contact
recreation 2 applies to water bodies where water recreation activities
that involve a significant risk of ingestion of water occur, but less
frequently than for primary contact recreation 1 due to:
      (i) physical characteristics of the water body; or

      (ii) limited public access.
    (C) Secondary contact recreation 1. Secondary contact
recreation 1 applies to water bodies where water recreation can occur,
but the nature of the recreation does not involve a significant risk
of ingestion. Secondary contact recreation 1 applies to intermittent
and perennial freshwaters where site-specific information demonstrates
that primary contact recreation 1 or 2 have little to no likelihood
of occurring. At a minimum, the following characteristics must be
demonstrated for a presumed use of secondary contact recreation 1
to apply:
      (i) during dry weather flows, the average depth at
the thalweg (mid-channel) is less than 0.5 meters and there are not
substantial pools with a depth of 1 meter or greater; and
      (ii) there are no existing recreational activities
that create a significant risk of ingestion or uses for primary contact
recreation 1 or 2.
    (D) Secondary contact recreation 2. Secondary contact
recreation 2 applies to water bodies where water recreation activities
do not involve a significant risk of water ingestion and where activities
occur less frequently than for secondary contact recreation 1 due
to physical characteristics of the water body or limited public access.
No water body is presumed to have a use of secondary contact recreation
2. This use is applicable when designated for an individual water
body as listed in Appendix A or G in §307.10 of this title.
    (E) Noncontact recreation. Noncontact recreation applies
to water bodies where recreation activities do not involve a significant
risk of water ingestion and where primary and secondary contact recreation
uses should not occur because of unsafe conditions. No water body
is presumed to have a use of noncontact recreation. This use is applicable
when designated for an individual water body as listed in Appendix
A or G in §307.10 of this title.
  (3) Assigning recreational uses to an unclassified
water body.
Cont'd...