Section 18 AAC 80.655 - General monitoring requirements(a) With respect to the monitoring requirements of 40 C.F.R. 141.74(b) and (c), adopted by reference under 18 AAC 80.010(a), with which the owner or operator of a community water system, non-transient non-community water system, or transient non-community water system using a surface water source or a GWUDISW source must comply, the department will (1) under 40 C.F.R. 141.74(b)(6)(i) and (c)(3)(i), allow disinfectant residual samples to be taken at points other than the total coliform sampling points described in the sample siting plan required under 18 AAC 80.410, if the department determines that those alternative points are more representative of disinfected water quality within the distribution system; to seek department approval under this paragraph for a system that uses groundwater combined with either surface water or GWUDISW, the owner 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; if heterotrophic bacteria is measured instead of residual disinfectant concentration, it must be measured as heterotrophic plate count (HPC) under 40 C.F.R. 141.74(a), adopted by reference in 18 AAC 80.010(a);(2) for a system that does not provide filtration treatment, but for which the department has determined in writing that filtration is required, specify alternative monitoring requirements until filtration is in place.(b) For a system required to determine a total inactivation ratio, the total inactivation ratio may be based on the CT99.9 values in tables 1.1 - 1.6, 2.1, and 3.1 in 40 C.F.R. 141.74(b)(3), adopted by reference in 18 AAC 80.010(a), or on the CT values calculated using the following formula: CT = (log inactivation)(5.057)(ea)(eb)(ec)
where:
log inactivation can vary from 0.5 to 3;
e =natural logarithm, approximately 2.71828;
a = -0.0693 x temperature in degrees Celsius;
b = 0.361 x pH;
c = 0.113 x chlorine concentration in mg/l;
(c) Under 40 C.F.R. 141.74(b)(2) and (c)(1), adopted by reference in 18 AAC 80.010(a), the department will approve continuous monitoring for a system 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 40 C.F.R. 141.71(a)(2), adopted by reference in 18 AAC 80.010(a), for a system that does not provide filtration treatment.(d) The department will not grant an exemption from the requirements of 40 C.F.R. 141.72(a)(3) or (b)(2), adopted by reference in 18 AAC 80.010(a).Eff. 10/1/99, Register 151; am 1/11/2006, Register 177; am 11/9/2006, Register 180; am 4/24/2009, Register 190; am 2/11/2017, Register 221, April 2017 Authority:AS 46.03.020
AS 46.03.050
AS 46.03.710
AS 46.03.720