Current through September 17, 2024
006.01 Systems
required to conduct source water monitoring must collect samples for each plant
that treats a surface water or GWUDI source. Where multiple plants draw water
from the same influent, such as the same pipe or intake, the Department may
approve one set of monitoring results to be used to satisfy the source water
monitoring requirements for all plants.
006.02 Systems That Add Chemicals
25-006.02A Systems must collect source water
samples prior to chemical treatment, such as coagulants, oxidants and
disinfectants, unless the system meets the condition of 179 NAC
25-006.02B.
25-006.02B The Department may approve a
system to collect a source water sample after chemical treatment. To grant this
approval, the Department must determine that collecting a sample prior to
chemical treatment is not feasible for the system and that the chemical
treatment is unlikely to have a significant adverse effect on the analysis of
the sample.
006.03
Systems that recycle filter backwash water must collect source water samples
prior to the point of filter backwash water addition.
006.04 Bank Filtration
25-006.04A Systems that receive
Cryptosporidium treatment credit for bank filtration under 179
NAC 17-005.02 or 179 NAC 19-009.03 as applicable, must collect source water
samples in the surface water prior to bank filtration.
25-006.04B Systems that use bank filtration
as pretreatment to a filtration plant must collect source water samples from
the well (i.e., after bank filtration). Use of bank filtration during
monitoring must be consistent with routine operational practice. Systems
collecting samples after a bank filtration process may not receive treatment
credit for the bank filtration under 179 NAC 25-019.03.
006.05 Multiple Sources
Systems with plants that use multiple water sources,
including multiple surface water sources and blended surface water and ground
water sources, must collect samples as specified in 179 NAC
25-006.05A or
25-006.05B. The
use of multiple sources during monitoring must be consistent with routine
operational practice.
25-006.05A If a
sampling tap is available where the sources are combined prior to treatment,
systems must collect samples from the tap.
25-006.05B If a sampling tap where the
sources are combined prior to treatment is not available, systems must collect
samples at each source near the intake on the same day and must follow either
179 NAC
25-006.05B1 or
25-005.05B2 for
sample analysis.
25-006.05B1 Systems may
composite samples from each source into one sample prior to analysis. The
volume of sample from each source must be weighted according to the proportion
of the source in the total plant flow at the time the sample is
collected.
25-006.05B2 Systems may
analyze samples from each source separately and calculate a weighted average of
the analysis results for each sampling date. The weighted average must be
calculated by multiplying the analysis result for each source by the fraction
the source contributed to total plant flow at the time the sample was collected
and then summing these values.
006.06 Additional Requirements
Systems must submit a description of their sampling
location(s) to the Department at the same time as the required sampling
schedule. This description must address the position of the sampling location
in relation to the system's water source(s) and treatment processes, including
pretreatment, points of chemical treatment, and filter backwash recycle. If the
Department does not respond to a system regarding sampling location(s), the
system must sample at the reported location(s).
