18 AAC 80.665. Monitoring requirements for filtered systems

(a) In addition to the requirements of 18 AAC 80.655, the owner or operator of a Class A or Class B public water system that uses a surface water source or a GWUDISW source and that provides filtration treatment shall meet the monitoring requirements of this section.

(b) Except as described in (c) and (d) of this section, turbidity measurements as required by 18 AAC 80.650 must be performed on representative samples of the system's filtered water at least every four hours during which the system filters water. The owner or operator may substitute continuous turbidity monitoring for grab sample monitoring if the owner or operator validates the continuous measurement for accuracy on a regular basis using a method approved under (e) of this section.

(1) serves 500 or fewer individuals; and

(2) uses slow sand filtration or a filtration treatment other than conventional treatment, direct filtration, or diatomaceous earth filtration.

(d) The department will reduce the turbidity sampling frequency required in (b) of this section to once each day using the procedure in (f) of this section if the department finds that less frequent monitoring is sufficient to indicate effective filtration performance for a system

(1) serving more than 500 individuals and using slow sand filtration or a filtration treatment other than conventional treatment, direct filtration, or diatomaceous earth filtration; or

(2) serving 500 or fewer individuals and using conventional treatment, direct filtration, or diatomaceous earth filtration.

(e) The department will approve continuous monitoring if the turbidimeter is properly operated and is calibrated and validated at the frequency recommended by the manufacturer, or at least weekly, whichever is more frequent. In determining the percent of turbidity readings exceeding limits when a system uses continuous monitoring, the operator shall use the turbidity levels reading from the strip chart or other record every four hours, beginning with the reading at midnight. This method will also apply to a "turbidity event" under 18 AAC 80.620(b) (2) for unfiltered systems.

(f) To reduce turbidity monitoring required under (b) of this section, the owner or operator shall submit a written request to the department, including turbidity monitoring data for the previous 12 months. The department will reduce the monitoring frequency if the owner or operator has continuously met the applicable turbidity requirements of 18 AAC 80.650(b) - (e) during those 12 months.

History: Eff. 10/1/99, Register 151

Authority: AS 46.03.020

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