1. (a) Construction. Construction material for an aeration basin and a clarifier must resist the effects of a corrosive wastewater environment.

2. (b) Freeboard.

   1. (1) An aeration basin must have a minimum freeboard of 18 inches at the peak flow.
   2. (2) A clarifier must have a minimum freeboard of 12 inches at the peak flow.

3. (c) Redundancy and Flow Control.

   1. (1) A facility with a design flow of equal to or greater than 0.4 million gallons per day (mgd) must have a minimum of two aeration basins and two clarifiers, unless the aeration equipment is removable without taking the aeration basin out of service.
   2. (2) Internal and interconnecting pipes must be capable of hydraulically passing the peak flow without overflow and with either the largest clarifier or the largest aeration basin out of service.
   3. (3) Each aeration basin and clarifier must have gates or valves to allow it to be hydraulically isolated.
   4. (4) Each aeration basin and clarifier must have a dedicated means for dewatering.

Source Note:The provisions of this §217.153 adopted to be effective August 28, 2008, 33 TexReg 6843.