Current through Register Vol. 18, September 20, 2024
(1) The
department adopts and incorporates by reference
40 CFR
141.13,
141.73,
141.173,
141.550, and
141.551, which set forth maximum
contaminant levels for turbidity, except for the following changes:
(a) The terms "one turbidity unit" and "1 NTU"
mean 1.0 nephelometric turbidity unit, and the terms "five turbidity units" and "5
NTU" mean 5.0 nephelometric turbidity units for the purposes of this
subchapter.
(b) The following replaces
40 CFR 141.73(a)
(1): "For systems using conventional filtration or
direct filtration, the turbidity level of representative samples of the system's
combined filtered water must be less than or equal to 0.5 NTU in at least 95% of the
measurements taken each month, and may not at any time exceed 1.0 NTU."
(c) The following replaces
40 CFR 141.73(a)
(2), and is also added at the end of
40 CFR
141.173(a) (1) and
141.551: "For systems using
conventional filtration or direct filtration, the turbidity level of representative
samples of a system's effluent from individual filters, measured at a point prior to
mixing with effluent from other filters or other sources, may not exceed 0.5 NTU in
at least 95% of the measurements taken each month, and may not at any time exceed
5.0 NTU. This requirement is not violated if the turbidity reading for the effluent
from each individual filter is the first reading of the month that exceeds 0.5 NTU
and the individual filter is taken off-line within 24 hours after the sample
analysis that shows the exceedance."
(d)
The first sentence in 40 CFR
141.551 is replaced with the following sentence:
"Your system must meet three strengthened combined filter effluent turbidity
limits."
(2) The department
may invalidate a turbidity measurement based on documentation that demonstrates the
exceedance was caused by turbidimeter performance difficulty or sample site location
problems and that the measurements were not indicative of true water quality. If the
department invalidates the turbidity reading on one of these bases, the turbidity
reading may not be included in the 95% compliance calculations required under this
rule.
