| (a) The effluent sets in §309.4 of this title
(relating to Table 1, Effluent Limitations for Domestic Wastewater
Treatment Plants) are intended to represent standard levels of treatment
normally required for domestic wastewater treatment plants.
(b) Modifications to the effluent sets listed in §309.4
of this title may be considered by the commission when effluent limits
more stringent than secondary treatment are required in order to maintain
desired water quality levels.
(c) On a case-by-case basis, modifications to the effluent
sets listed in §309.4 of this title may be considered by the
commission for certain existing, natural systems which cannot consistently
meet pH or total suspended solids (TSS) limitations due to the inherent
variability of a particular system. Modifications to the effluent
sets may be allowed for a natural system designed for treatment or
polishing with a discharge directly into surface water in the state.
Natural systems include, but are not necessarily limited to, aerated
lagoons followed by stabilization ponds, facultative ponds, stabilization
ponds, and constructed wetlands. For the purpose of this chapter,
playa lakes are not considered natural systems. The commission will
consider the following factors in approving a modification to the
effluent sets:
(1) Any modification shall not allow a discharge which
would cause a violation of the commission's surface water quality
standards or any applicable total maximum daily loads or wasteload
evaluation.
(2) A proposal for a modification must be supported
by an engineering report, prepared and sealed by a licensed Texas
professional engineer representing the permit applicant, which justifies
the request for modification with specific information relating to
the proposed design and that design's inherent limitations. For considering
a request for modification of an existing system that cannot achieve
permitted pH or TSS limitations, the engineering report must also
document past efforts of design modification, operation, and maintenance,
and include data showing for the past three years, influent and effluent
hydraulic and organic loadings and the resultant effluent quality
achieved.
(3) The commission may set narrative effluent limitations
and effluent monitoring requirements as an alternative to a specific
numerical effluent limitation when a specific numeric effluent limitation
cannot be met because of, but not limited to, seasonal or operational
factors. These narrative requirements shall ensure that necessary
operational and maintenance actions are consistently carried out by
the permittee to meet applicable water quality standards. The commission
may request resumption of the original numerical limitations during
the next permit renewal or amendment based on a review of the discharge
effluent data.
(4) The commission may suspend setting a specific numerical
effluent limitation for a temporary period of time not to exceed the
remainder of the permit term, pending a review of the actual performance
of a natural system's design as long as the facility meets paragraph
(1) of this subsection. During any temporary suspension, the permittee
must document that the system is operated and maintained for optimal
performance in accordance with an operation and maintenance manual
prepared in accordance with Chapter 217 of this title (relating to
Design Criteria for Domestic Wastewater Systems) or Chapter 317 of
this title (relating to Design Criteria Prior to 2008) as applicable
and is meeting water quality standards. After review of performance
data and related information submitted by the permittee in a permit
application, for permit renewal or amendment, or when submitted at
the request of the executive director, the commission may set specific
numerical effluent limitations consistent with this subchapter and
the performance documented for the particular system.
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| Source Note: The provisions of this §309.2 adopted to be effective July 27, 1988, 13 TexReg 3514; amended to be effective June 5, 1998, 23 TexReg 5723; amended to be effective January 9, 2020, 45 TexReg 370 |
