Texas Administrative Code › Title 30 - ENVIRONMENTAL QUALITY › Part 1 - TEXAS COMMISSION ON ENVIRONMENTAL QUALITY › Chapter 309 - DOMESTIC WASTEWATER EFFLUENT LIMITATION AND PLANT SITING › Subchapter A - EFFLUENT LIMITATIONS › Section 309.2 - Rationale for Effluent Sets

Current through Reg. 49, No. 28; July 12, 2024
(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.