18 AAC 80.655. General monitoring requirements

(a) This section and the applicable requirements of 18 AAC 80.660 or 18 AAC 80.665 apply to the owner or operator of a community water system, non-transient non-community water system, or transient non-community water system using

(1) a surface water source;

(2) a GWUDISW source, beginning when disinfection is installed and no later than six months after the department determines that the groundwater source is under the direct influence of surface water; or

(3) water from any source if that system chlorinates.

(b) Failure to comply with this subsection is a treatment technique violation. The owner or operator of a public water system serving more than 3,300 individuals shall continuously monitor the residual disinfectant concentration of the water entering the distribution system and record the lowest value each day. If the continuous monitoring equipment fails, the owner or operator may conduct grab sampling every four hours instead of continuous monitoring, for no more than five working days after the equipment fails. The owner or operator of a public water system serving 3,300 or fewer individuals may take grab samples instead of providing continuous monitoring at the frequency required in Table H of this subsection.

TABLE H. GRAB SAMPLE FREQUENCIES FOR SYSTEMS USING SURFACE WATER OR GWUDISW SOURCES AND SERVING 3,300 OR FEWER INDIVIDUALS

System size by population Samples/day 500 or fewer 1 501 - 1,000 2* 1,001 - 2,500 3* 2.501 - 3,300 4*

*For a system serving more than 500 individuals, the daily samples must be taken at different times during the day. The sampling intervals are subject to department review and approval, based on whether those intervals serve the interests of public health.

(c) If the residual disinfectant concentration of the water entering the distribution system falls below 0.2 mg/l in a system using grab sampling instead of continuous monitoring, the owner or operator shall take a grab sample every four hours until the residual concentration is equal to or greater than 0.2 mg/l.

(d) The residual disinfectant concentration in the distribution system must be measured at least at the same points in the distribution system and at the same time as total coliforms are sampled, as described at 18 AAC 80.400 - 18 AAC 80.425. If the department finds that other points are more representative of disinfected water quality within the distribution system, the department will allow the owner or operator of a public water system that uses groundwater combined with either a surface water source or a GWUDISW source to take disinfectant residual samples at points other than the total coliform sampling points. Heterotrophic bacteria, measured as heterotrophic plate count (HPC) under 18 AAC 80.1100(k), may be measured instead of residual disinfectant concentration. To seek department approval for alternate distribution system residual disinfectant concentration sampling plans for a filtered or unfiltered system that uses groundwater combined with either surface water or GWUDISW, the owner or operator must submit a request for alternate sampling locations. The request must include the disinfectant residual sample siting plan approved by the department showing each proposed alternative sampling location, a narrative rationale for relocation of the sampling site, a description or ratio of flow of groundwater and surface water at the proposed location, the mixing zone pipe length, and the velocity of flow. As a condition for approval of an alternative sampling site, the department will require additional monitoring as the department considers necessary to verify that the disinfectant residual limit of 0.2 mg/l is being met at the approved location.

History: Eff. 10/1/99, Register 151; am 1/11/2006, Register 177

Authority: AS 46.03.020

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