26.04.01.12

.12 Turbidity Sampling and Analytical Requirements.

A. A supplier of water using a surface water source or a ground water source under the direct influence of surface water shall perform turbidity monitoring as required by 40 CFR §§141.70—141.75.

B. Filtered and unfiltered public water systems using surface water sources shall also comply with C and D of this regulation until June 29, 1993. A supplier of water using unfiltered surface water or ground water under the direct influence of surface water, which is required by the Approving Authority to filter, but which has not installed filtration, shall continue to comply with C and D of this regulation until filtration is installed, even beyond June 29, 1993.

C. The supplier of water shall take samples at a representative entry point to the water distribution system at least once per day for the purpose of making turbidity measurements to determine compliance with Regulation .08 of this chapter.

D. If a measurement indicates the maximum allowable limit has been exceeded, the sampling and measurements shall be repeated, preferably in 1 hour. If the repeat sample confirms that the maximum allowable limit has been exceeded, the supplier of water shall report to the Approving Authority as directed in Regulation .19 of this chapter. If the results of the repeat sample are less than the first sample, the second value should be used in the calculation of the monthly average; otherwise, repeat samples may not be used in calculating the monthly average. If the monthly average of the daily samples exceeds the maximum allowable limit, or if the average of two samples taken on consecutive days exceeds 5 TU, the supplier of water shall notify the Approving Authority as directed in Regulation .19 of this chapter and shall notify the public as directed in Regulation .20 of this chapter.

E. Measurements of turbidity shall be made by the Nephelometric Method in accordance with the methods specified in 40 CFR 141.74(a)(1). Continuous turbidity monitoring may be used by a supplier of water only with approval by the Approving Authority.

F. Suppliers of water at systems serving 10,000 or more individuals shall meet the turbidity monitoring requirements in 40 CFR §141.173(a) in addition to the requirements of §§A—E of this regulation.

G. Suppliers of water at systems serving fewer than 10,000 individuals shall meet the turbidity monitoring requirements in 40 CFR §§141.550—141.564 in addition to the requirements of §§A—E of this regulation.