1. (a) The components of an alternative collection system must be sized based on existing flow data from a system and service area with similar characteristics, if such data is available. Similar characteristics for sizing alternative collection systems include:

   1. (1) location;
   2. (2) inflow and infiltration characteristics;
   3. (3) peak flows;
   4. (4) pipe materials;
   5. (5) customer base, including sources of wastewater and percent contribution from the wastewater sources; and
   6. (6) any other characteristics required by the executive director.
2. (b) If flow data from a similar service area with a conventional collection system is used, the engineering report must include the expected effects of inflow and infiltration on the peak flow of the conventional collection system.
3. (c) Design and construction of an alternative collection system must minimize excess flows from inflow and infiltration.
4. (d) Roof drains, street drains, or other types of drains that allow entrance of stormwater into an alternative collection system are prohibited.
5. (e) In the absence of existing data, the sizing of on-site components in an alternative collection system must be based on Table B.1. in Figure: 30 TAC §217.32(a)(3) of this title (relating to Organic Loadings and Flows for New Wastewater Treatment Facilities), in conjunction with the following equation:
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6. (f) Design of the off-site components must be based on the maximum flow rate expected, calculated using the following equation:
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   1. (1) An equivalent dwelling unit (EDU) is assumed to have an occupancy of 3.5 people. For EDU populations greater than 3.5, the following equation must be used:
      Attached Graphic
      
   2. (2) The safety factor, "B," may be adjusted if higher wastewater flows are anticipated. A discharge from commercial or institutional dischargers must be measured directly or calculated under this subsection.

Source Note:The provisions of this §217.92 adopted to be effective August 28, 2008, 33 TexReg 6843; amended to be effective December 4, 2015, 40 TexReg 8254.