A public water system that uses a surface water source or a groundwater source under the influence of surface water must monitor in accordance with this section beginning July 1, 1993.

1. (1) Turbidity measurements as required by §290.118 of this title (relating to Filtration) must be performed on representative samples of the system's filtered water every four hours (or more frequently) that the system serves water to the public. A public water system may substitute continuous turbidity monitoring for grab sample monitoring if it validates the continuous measurement for accuracy by calibrating on a weekly basis as a minimum frequency. Continuous monitoring results must be reported at equal intervals of four hours or less. For systems serving 500 or fewer persons, the system may reduce the turbidity sampling frequency to once per day.
2. (2) The residual disinfectant concentration of the water entering the distribution system must be monitored continuously, and the lowest value must be recorded each day. The system must also record the duration of the longest event when the residual leaving the plant fell below 0.2 mg/liter free chlorine or 0.5 mg/liter chloramine. Continuous disinfectant monitoring equipment must be calibrated at minimum frequency of monthly. If there is a failure in the continuous monitoring equipment, grab sampling every four hours may be conducted in lieu of continuous monitoring, but for no more than five working days following the failure of the equipment. Systems serving 3,300 or fewer persons may take grab samples in lieu of providing continuous monitoring on an ongoing basis at the frequencies each day as prescribed in the following chart. Systems which sell water on a wholesale basis shall monitor the disinfectant residual leaving the plant based on the total number of connections served by the wholesale provider and its wholesale customers. If at any time the residual disinfectant concentration falls below 0.2 mg/liter free chlorine or 0.5 mg/liter chloramine in a system using grab sampling in lieu of continuous monitoring, the system must take a grab sample every four hours until the residual disinfectant concentration meets the disinfectant requirement.

Source Note:The provisions of this §290.119 adopted to be effective April 15, 1994, 19 TexReg 2282; amended to be effective December 7, 1994, 19 TexReg 9368.