(a) The permittee shall use the following design components for subsurface area drip dispersal systems:
  (1) a minimum of dual 100-micron wastewater effluent filters prior to the effluent entering the subsurface area drip dispersal system. These filters must:
    (A) effectively filter the peak hydraulic flows; and
    (B) include control valves and piping that provide filtered effluent to flush the filters;
  (2) the dosing tank(s) designed to hold at least the following volume:
    (A) the daily design capacity required by the permit;
    (B) effluent equal to six times the minimum dose cycle capacity of the drip lines plus the capacity of the supply and return manifold; and
    (C) the following storage capacities as part of the dosing tank(s) or included in the plant design at another location:
      (i) flow equalization storage;
      (ii) emergency storage; and
      (iii) return flows from flushing and system drainage;
  (3) a duplex alternating pumping system designed:
    (A) to dose and flush the dispersal zones and flush the filtration system; and
    (B) with pumps sized in accordance with the hydraulic design calculations in §222.83 of this title (relating to Hydraulic Calculations);
  (4) control system components that are capable of performing the following functions:
    (A) flushing of the filter units;
    (B) delivering a specified preprogrammed volume of effluent to each dispersal zone;
    (C) flushing of each drip lateral with filtered effluent;
    (D) dosing of chemicals intended to reduce emitter clogging, such as chlorine or oxidizing chemicals;
    (E) monitoring alarm conditions;
    (F) regulating the flow volume to each dispersal zone and to a sand filter, when applicable;
    (G) indicating a flow variance when flow varies more than 10% of the actual average daily flow;
    (H) regulating pump run times;
    (I) regulating the number and time of filter backwash and field flushing cycles; and
    (J) regulating the flows to the drip irrigation field system;
  (5) supply lines and manifolds;
  (6) zones of drip irrigation tubing;
  (7) effluent manifolds;
  (8) chemical dosing equipment; and
  (9) flush return lines that return flushing water to the pre-application system, with provisions made to minimize disturbance of any solids in the settling chamber.
(b) The permittee shall submit the hydraulic calculations for the pump and distribution system with the engineering report. The report must address the following.
  (1) Field pressure and flow variation due to friction loss and changes in static head must not exceed plus or minus 10% of the design emitter pressure or flow. The 10% difference must be the difference between any two emitters in the entire system after the start-up process is complete.
  (2) The system must be equipped an alarm system for high and low flow conditions and an automatic mechanism to shut down the dispersal system for pressure and flow conditions that would indicate abnormal fluid dynamics were occurring.
(c) The permittee shall design the subsurface area drip dispersal system to supply the effluent uniformly throughout each of the dispersal zones in the system.
(d) The permittee shall design the subsurface area drip dispersal system to be self-draining to prevent freezing if there is a potential for the soil to freeze to the depth that the pipes and lines of the subsurface area drip dispersal system are located.
(e) The permittee shall ensure that the velocity of the flush water shall be at least two feet per second at the end of each dispersal zone or return line during the flushing operation.
(f) The permittee shall equip the system with a backflow prevention device to prevent the siphoning of soil and water into the emitters.
(g) The permittee must establish stormwater run-on controls to minimize infiltration of precipitation into the dispersal zones.

Source Note: The provisions of this §222.117 adopted to be effective July 5, 2006, 31 TexReg 5308