1. (a) This section applies to the storage of residuals after processing but before final disposal or removal from the facility site.
2. (b) A site may store residuals in liquid, dewatered, or dry form if the solids have been stabilized in a treatment process.

3. (c) General Storage Requirements.

   1. (1) The design of a storage facility must minimize odor conditions and vector attraction.
   2. (2) A storage facility must provide storage of waste sludge separate from a biological treatment process.
   3. (3) The design of a storage facility must be based on process design, sludge age, waste stream concentration, operational hours, operational volume in tanks, decant or dewatering volumes and characteristics, time frames needed for decanting or dewatering, and volume needed for storage and sampling.
   4. (4) The report must include a solids management plan that demonstrates a method of managing the waste solids that will maintain the design sludge age for a biological process.

4. (d) Storage of Solids - Not Dewatered.

   1. (1) Aerobically Digested Solids.

      1. (A) A storage facility may store aerobically digested solids.
      2. (B) A basin must have diffused air or mechanical mixing.
      3. (C) A diffused air-mixing unit must provide a minimum air capacity of 30 standard cubic feet per minute per 1,000 cubic feet (cf) of volume.
      4. (D) A mechanical surface aerator must have a minimum of 1.0 horsepower per 1,000 cf of volume.
      5. (E) An earthen basin must be lined in accordance with §217.203(c) and (d) of this title (relating to Design Criteria for Natural Treatment Facilities).
   2. (2) Anaerobically Digested Solids. Anaerobically digested solids may be stored in a covered basin.

5. (e) Storage of Dewatered Solids.

   1. (1) A storage facility must store the dewatered solids in a container or in a stockpile that prevents re-wetting by precipitation.
   2. (2) A storage container may store dewatered solids with a solids content of less than 35% for no more than seven days.
   3. (3) A storage facility must store dewatered solids in a steel or concrete container that prevents re-wetting by precipitation.
   4. (4) A storage facility may store dewatered solids with a solids content of at least 35% but not more than 50% for no more than 90 days.

6. (f) Open Stockpiles.

   1. (1) An open stockpile must have an impervious pad underneath the solids to prevent groundwater contamination.
   2. (2) An open stockpile must have a system for collecting storm water runoff and returning it to the head of the treatment facility.

7. (g) Dried Solids Storage.

   1. (1) A storage facility may store dewatered solids with a solids content of greater than or equal to 50% in a bin or covered facility.
   2. (2) A enclosed storage structure must be mechanically ventilated with at least 20 air exchanges per hour and must have an odor control system for the exhaust.

Source Note:The provisions of this §217.251 adopted to be effective August 28, 2008, 33 TexReg 6843.