1. (a) The design of a new facility must be based on the flows and loadings in paragraphs (1) - (3) of this subsection, unless subsection (b) of this section applies.

   1. (1) Design flow.

      1. (A) For a facility equal to or greater than 1.0 million gallons per day (mgd), the permitted flow is the average annual flow value determined by multiplying the per capita flow in Table B.1. in paragraph (3) of this subsection by the number of people in the service area.
      2. (B) For a facility less than 1.0 mgd, the permitted flow is the maximum 30-day average flow estimated by multiplying the average annual flow by a factor of at least 1.5.

   2. (2) Peak flow. When site-specific data is unavailable, the instantaneous two-hour peak flow must be estimated by multiplying the permitted flow by a factor of 4.0.

      1. (A) If a facility experiences unusual periodic flow variations, a higher multiplier may be used to calculate the peak flow.
      2. (B) In a facility with flow equalization, the facility may be designed for a lower estimated peak flow, if supporting data included in the report supports the estimate.
      3. (C) A treatment unit, pipe, weir, flume, disinfection unit, or any other treatment unit that is flow limited must be sized to transport or treat the estimated peak flow.
      4. (D) A facility must use a totalizing flow meter for flow measurement.
   3. (3) Design organic loading. If available, actual organic loading data must be used as the basis for design. If actual data is not available, the design organic load must be used as the basis for design. The design organic load is determined by multiplying the projected uses by annual average flow determined from the following table and by using the appropriate influent concentration from the following table:
      Attached Graphic
      
2. (b) For an owner constructing a new system to serve the same service area as an existing facility with sufficient historical data, the data from §217.34 of this title (relating to Re-Rating, Expanding, or Materially Altering an Existing Facility), may be used to design a wastewater treatment facility if justified in the report.

Source Note:The provisions of this §217.32 adopted to be effective August 28, 2008, 33 TexReg 6843.