(a) Authorized bypass. The permittee may allow any bypass to occur from a TPDES permitted facility which does not cause effluent limitations to be exceeded, but only if it also is for essential maintenance to assure efficient operation. These bypasses are not subject to the provisions of subsections (b) and (c) of this section.
(b) Notice.
  (1) Anticipated bypass. In accordance with the procedures described in Chapter 35 of this title (relating to Emergency and Temporary Orders and Permits; Temporary Suspension or Amendment of Permit Conditions), if the permittee knows in advance of the need for a bypass, it shall submit prior notice under §35.24 of this title (relating to Application for Emergency or Temporary Order) if possible at least ten days before the date of the bypass.
  (2) Unanticipated bypass. The permittee shall submit notice of an unanticipated bypass as required in §305.125(9) of this title (relating to Standards Permit Conditions (24-hour notice)).
(c) Prohibition of bypass.
  (1) Bypass of untreated or partially treated wastewater is prohibited from a TPDES permitted facility, and the commission may take enforcement action against the permittee for bypass, unless all of the following conditions are met:
    (A) Bypass was unavoidable to prevent loss of life, personal injury, or severe property damage;
    (B) there were no feasible alternatives to the bypass, such as the use of auxiliary treatment facilities, retention of untreated wastes, or maintenance during normal periods of equipment downtime. This condition is not satisfied if adequate back-up equipment should have been installed in the exercise of reasonable engineering judgment to prevent a bypass which occurred during normal periods of equipment downtime or preventive maintenance;
    (C) the permittee submitted notices as required under subsection (b) of this section.
  (2) The commission may approve an anticipated bypass in accordance with the procedures described in Chapter 35 of this title (relating to Emergency and Temporary Orders and Permits; Temporary Suspension or Amendment of Permit Conditions), after considering its adverse effects, if the commission determines that it will meet the three conditions listed in paragraph (1) of this subsection.
(d) Establishing Limitations, Standards, and Other Conditions in TPDES Permits.
  (1) Permits for POTWs shall contain technology-based treatment requirements based upon secondary treatment and "best practical waste treatment technology."
  (2) This paragraph describes the minimum level of effluent quality attainable by POTWs in terms of the parameters of five-day biochemical oxygen demand (BOD[sub]5[/sub]), total suspended solids (TSS), and pH. All requirements shall be achieved except as provided for in this subsection.
    (A) For BOD[sub]5[/sub], the 30-day average shall not exceed 30 mg/l and the 7-day average shall not exceed 45 mg/l. The 30-day average percent removal shall not be less than 85%. At the option of the commission, in lieu of the BOD[sub]5[/sub] parameter, the parameter five-day carbonaceous biochemical oxygen demand (CBOD[sub]5[/sub]) may be substituted. For CBOD[sub]5[/sub], the 30-day average shall not exceed 25 mg/l and the 7-day average shall not exceed 40 mg/l. The 30-day average percent removal shall not be less than 85%.
    (B) For TSS, the 30-day average shall not exceed 30 mg/l and the 7-day average shall not exceed 45 mg/l. The 30-day average percent removal shall not be less than 85%.
    (C) For pH, the effluent values for pH shall be maintained within the limits of 6.0 and 9.0 unless the POTW demonstrates that inorganic chemicals are not added to the waste stream as part of the treatment process and contributions from industrial sources do not cause the pH of the effluent to be less than 6.0 or greater than 9.0.
  (3) Treatment works shall be eligible for consideration of effluent limitations described for treatment equivalent to secondary treatment, as described in 40 CFR §133.105, if the BOD[sub]5[/sub] and TSS effluent concentrations consistently achievable through proper maintenance and operation of the treatment works exceed the minimum level of the effluent quality set forth in paragraph (2)(A) and (2)(B) of this subsection, a trickling filter or waste stabilization pond is used as the principal process, and the treatment works provide significant biological treatment of municipal wastewater.
  (4) The minimum TSS effluent quality concentration achievable with waste stabilization ponds may be adjusted in accordance with 40 CFR §133.103(c).
  (5) The commission is authorized to substitute either a lower percent removal requirement or a mass loading limit for a percent removal requirement set forth in this subsection provided the permittee satisfactorily demonstrates that:
    (A) The treatment works is consistently meeting, or will consistently meet, its permit effluent concentration limits but its percent effluent removal requirements cannot be met due to a less concentrated influent wastewater;
    (B) To meet the percent removal requirements, the treatment works would have to achieve significantly more stringent limitations than would otherwise be required by the concentration-based standards (where the term "significantly more stringent limitations" means BOD[sub]5[/sub] and TSS limitations necessary to meet the percent removal requirements of at least 5 mg/l more stringent than the otherwise applicable concentration-based limitations of this subsection, if such limits would, by themselves, force significant construction or other significant capital expenditure); and
    (C) The less concentrated influent wastewater is not the result of excessive inflow or infiltration (I/I). The determination of whether the less concentrated wastewater is not the result of excessive I/I will be based upon the following definitions and criteria:
      (i) Excessive infiltration/inflow is the quantity of infiltration/inflow which can be economically eliminated from a sewer system as determined in a cost-effectiveness analysis that compares the costs for correcting the infiltration/inflow conditions to the total costs for transportation and treatment of the infiltration/inflow.
      (ii) Nonexcessive infiltration is the quantity of flow which is less than 120 gallons per capita per day (domestic base flow and infiltration) or the quantity of infiltration which cannot be economically and effectively eliminated from a sewer system as determined in a cost-effectiveness analysis.
      (iii) Nonexcessive inflow is the maximum total flow rate during storm events which does not result in chronic operational problems related to hydraulic overloading of the treatment works or which does not result in a total flow of more than 275 gallons per capita per day (domestic base flow plus infiltration plus inflow). Chronic operational problems may include surcharging, backups, bypasses, and overflows.

Source Note: The provisions of this §305.535 adopted to be effective October 8, 1990, 15 TexReg 5492; amended to be effective December 1, 1997, 22 TexReg 11391; amended to be effective December 10, 1998, 23 TexReg 12440.