| (79) Total toxicity--Toxicity as determined by exposing
aquatic organisms to samples or dilutions of instream water or treated
effluent. Also referred to as whole effluent toxicity or biomonitoring.
(80) Toxic equivalency factor--A factor to describe
an order-of-magnitude consensus estimate of the toxicity of a compound
relative to the toxicity of 2,3,7,8-tetraclorodibenzo-p-dioxin (2,3,7,8-TCDD).
The factor is applied to transform various concentrations of dioxins
and furans or dioxin-like polychlorinated biphenyls into equivalent
concentrations of 2,3,7,8-TCDD, expressed as a toxic equivalency.
(81) Toxic equivalency--The sum of the products from
the concentration of each dioxin and furan, or dioxin-like polychlorinated
biphenyl congener, multiplied by its respective toxic equivalency
factor to give a single 2,3,7,8-tetraclorodibenzo-p-dioxin equivalent.
(82) Toxicity--The occurrence of adverse effects to
living organisms due to exposure to toxic materials. Adverse effects
caused by conditions of temperature and dissolved oxygen are excluded
from the definition of toxicity. With respect to the provisions of
§307.6(e) of this title (relating to Toxic Materials), which
concerns total toxicity and biomonitoring requirements, adverse effects
caused by concentrations of dissolved salts (such as sodium, potassium,
calcium, chloride, carbonate) in source waters are excluded from the
definition of toxicity. Source water is defined as surface water or
groundwater that is used as a public water supply or industrial water
supply (including a cooling-water supply). Source water does not include
brine water that is produced during the extraction of oil and gas,
or other sources of brine water that are substantially uncharacteristic
of surface waters in the area of discharge. In addition, adverse effects
caused by concentrations of dissolved salts that are added to source
water by industrial processes are not excluded from the requirements
of §307.6(e) of this title, except as specifically noted in §307.6(e)(2)(B)
of this title, which concerns requirements for toxicity testing of
100% effluent. This definition of toxicity does not affect the standards
for dissolved salts in this chapter other than §307.6(e) of this
title. The standards implementation procedures contain provisions
to protect surface waters from adverse effects of dissolved salts
and methods to address the effects of dissolved salts on total toxicity
tests.
(83) Toxicity biomonitoring--The process or act of
determining total toxicity. Documents that describe procedures for
toxicity biomonitoring are cited in §307.6 of this title (relating
to Toxic Materials). Also referred to simply as biomonitoring.
(84) Water-effect ratio (WER)--The WER is calculated
as the toxic concentration (LC50 ) of
a substance in water at a particular site, divided by the toxic concentration
of that substance as reported in laboratory dilution water. The WER
can be used to establish site-specific acute and chronic criteria
to protect aquatic life. The site-specific criterion is equal to the
WER times the statewide aquatic life criterion in §307.6(c) of
this title.
(85) Water quality management program--The agency's
overall program for attaining and maintaining water quality consistent
with state standards, as authorized under the Texas Water Code, the
Texas Administrative Code, and the federal Clean Water Act, §§106,
205(j), 208, 303(e) and 314 (33 United States Code, §§1251 et seq.).
(86) Wetland--An area (including a swamp, marsh, bog,
prairie pothole, or similar area) having a predominance of hydric
soils that are inundated or saturated by surface or groundwater at
a frequency and duration sufficient to support and that under normal
circumstances supports the growth and regeneration of hydrophytic
vegetation. The term "hydric soil" means soil that, in its undrained
condition, is saturated, flooded, or ponded long enough during a growing
season to develop an anaerobic condition that supports the growth
and regeneration of hydrophytic vegetation. The term "hydrophytic
vegetation" means a plant growing in: water or a substrate that is
at least periodically deficient in oxygen during a growing season
as a result of excessive water content. The term "wetland" does not
include irrigated acreage used as farmland; a man-made wetland of
less than one acre; or a man-made wetland where construction or creation
commenced on or after August 28, 1989, and that was not constructed
with wetland creation as a stated objective, including but not limited
to an impoundment made for the purpose of soil and water conservation
that has been approved or requested by soil and water conservation
districts. If this definition of wetland conflicts with the federal
definition in any manner, the federal definition prevails.
(87) Wetland water quality functions--Attributes of
wetlands that protect and maintain the quality of water in the state,
which include stormwater storage and retention and the moderation
of extreme water level fluctuations; shoreline protection against
erosion through the dissipation of wave energy and water velocity,
and anchoring of sediments; habitat for aquatic life; and removal,
transformation, and retention of nutrients and toxic substances.
(88) Zone of initial dilution--The small area at the
immediate point of a permitted discharge where initial dilution with
receiving waters occurs and that may not meet certain criteria applicable
to the receiving water. A zone of initial dilution is substantially
smaller than a mixing zone.
(b) Abbreviations. The following abbreviations apply
to this chapter:
(1) ALU--aquatic life use.
(2) AP--aquifer protection.
(3) AS--agricultural water supply.
(4) ASTER--Assessment Tools for the Evaluation of Risk.
(5) BAF--Bioaccumulation factor.
(6) BCF--bioconcentration factor.
(7) CASRN--Chemical Abstracts Service Registry number.
(8) CFR--Code of Federal Regulations.
(9) cfs--cubic feet per second.
(10) Cl-1 --chloride.
(11) CR--county road.
(12) DO--dissolved oxygen.
(13) E--exceptional aquatic life use.
(14) EPA--United States Environmental Protection Agency.
(15) degrees F--degrees Fahrenheit.
(16) FM--Farm to Market Road.
(17) ft3 /s--cubic feet
per second.
(18) H--high aquatic life use.
(19) HEAST--Health Effects Assessment Summary Tables.
(20) I--intermediate aquatic life use.
(21) IBWC--International Boundary and Water Commission.
(22) IH--Interstate Highway.
(23) IRIS--Integrated Risk Information System.
(24) IS--industrial water supply.
(25) km--kilometer.
(26) L--limited aquatic life use.
(27) M--minimal aquatic life use.
(28) m--multiplier.
(29) m/km--meters per kilometer.
(30) MCL--maximum contaminant level (for public drinking
water supplies).
(31) MDL--method detection limit.
(32) mg/L--milligrams per liter.
(33) mi--mile.
(34) mL--milliliter.
(35) MUD--municipal utility district.
(36) N--navigation.
(37) NCR--noncontact recreation.
(38) O--oyster waters.
(39) PCR--primary contact recreation.
(40) PS--public water supply.
(41) RfD--reference dose.
(42) RR--ranch road.
(43) 7Q2--seven-day, two-year low-flow.
(44) SCR--secondary contact recreation.
(45) SH--state highway.
(46) SO4 -2 --sulfate.
(47) SU--standard units.
(48) TCEQ--Texas Commission on Environmental Quality.
(49) TDS--total dissolved solids.
(50) TEF--toxic equivalency factor.
(51) TMDL--total maximum daily load.
(52) TPDES--Texas Pollutant Discharge Elimination System.
(53) TRE--toxicity reduction evaluation.
(54) TSS--total suspended solids.
(55) US--United States.
(56) USFDA--United States Food and Drug Administration.
(57) USGS--United States Geological Survey.
(58) WER--Water-effect ratio.
(59) WF--waterfowl habitat.
(60) WQM--water quality management.
(61) µg/L--micrograms per liter.
(62) ZID--zone of initial dilution.
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| Source Note: The provisions of this §307.3 adopted to be effective July 10, 1991, 16 TexReg 3400; amended to be effective July 13, 1995, 20 TexReg 4701; amended to be effective August 17, 2000, 25 TexReg 7722; amended to be effective July 22, 2010, 35 TexReg 6294; amended to be effective March 6, 2014, 39 TexReg 1450; amended to be effective March 1, 2018, 43 TexReg 1102; amended to be effective September 29, 2022, 47 TexReg 6216 |
