Current through September 17, 2024
Each system must complete the corrosion control treatment
requirements described below which are applicable to such system under 179 NAC
12-004.
005.01 System Recommendation Regarding
Corrosion Control Treatment
Based upon the results of lead and copper tap monitoring and
water quality parameter monitoring, small and medium-size water systems
exceeding the lead or copper action level must recommend installation of one or
more of the corrosion control treatments listed in 179 NAC 12-005.03A which the
system believes constitutes optimal corrosion control for that system. The
Director may require the system to conduct additional water quality parameter
monitoring in accordance with 179 NAC 12-010.02 to assist the Director in
reviewing the system's recommendation.
005.02 Director Decision to Require Studies
of Corrosion Control Treatment (Applicable to Small and Medium-Size Systems)
The Director may require any small or medium-size system that
exceeds the lead or copper action level to perform corrosion control studies
under 179 NAC 12-005.03 to identify optimal corrosion control treatment for the
system.
005.03 Performance
of Corrosion Control Studies
12-005.03A Any
public water system performing corrosion control studies must evaluate the
effectiveness of each of the following treatments, and, if appropriate,
combinations of the following treatments to identify the optimal corrosion
control treatment for that system:
1.
Alkalinity and pH adjustment;
2.
Calcium hardness adjustment; and
3.
The addition of a phosphate or silicate based corrosion inhibitor at a
concentration sufficient to maintain an effective residual concentration in all
test tap samples.
12-005.03B The water system must evaluate
each of the corrosion control treatments using either pipe rig/loop tests,
metal coupon tests, partial-system tests, or analyses based on documented
analogous treatments with other systems of similar size, water chemistry and
distribution system configuration.
12-005.03C The water system must measure the
following water quality parameters in any tests conducted under 179 NAC
12-005.03C before
and after evaluating the corrosion control treatments listed above:
1. Lead;
2. Copper;
3. pH;
4. Alkalinity;
5. Calcium;
6. Conductivity;
7. Orthophosphate (when an inhibitor
containing a phosphate compound is used);
8. Silicate (when an inhibitor containing a
silicate compound is used); and
9.
Water temperature.
12-005.03D The water system must identify all
chemical or physical constraints that limit or prohibit the use of a particular
corrosion control treatment and document such constraints with at least one of
the following:
1. Data and documentation
showing that a particular corrosion control treatment has adversely affected
other water treatment processes when used by another water system with
comparable water quality characteristics; and/or
2. Data and documentation demonstrating that
the water system has previously attempted to evaluate a particular corrosion
control treatment and has found that the treatment is ineffective or adversely
affects other water quality treatment processes.
12-005.03E The water system must evaluate the
effect of the chemicals used for corrosion control treatment on other water
quality treatment processes.
12-005.03F On the basis of an analysis of the
data generated during each evaluation, the water system must recommend to the
Director in writing the treatment option that the corrosion control studies
indicate constitutes optimal corrosion control treatment for that system. The
water system must provide a rationale for its recommendation along with all
supporting documentation specified in 179 NAC
12-005.03A
through
12-005.03E.
005.04 Designation of Optimal
Corrosion Control Treatment by the Director
12-005.04A Based upon consideration of
available information including, where applicable, studies performed under 179
NAC
12-005.03 and a system's
recommended treatment alternative, the Director must either approve the
corrosion control treatment option recommended by the system, or designate
alternative corrosion control treatment(s) from among those listed in 179 NAC
12-005.03A. When
designating optimal treatment the Director must consider the effects that
additional corrosion control treatment will have on water quality parameters
and on other water quality treatment processes.
12-005.04B The Director must notify the
system of its decision on optimal corrosion control treatment in writing and
explain the basis for this determination. If the Director requests additional
information to aid its review, the water system must provide the
information.
005.05
Installation of Optimal Corrosion Control
Each system must properly install and operate throughout its
distribution system the optimal corrosion control treatment designated by the
Director under 179 NAC 12-005.04.
005.06 Director Review of Treatment and
Specification of Optimal Water Quality Control Parameters
The Director must evaluate the results of all lead and
copper tap samples and water quality parameter samples submitted by the water
system and determine whether the system has properly installed and operated the
optimal corrosion control treatment designated by the Director in 179 NAC
12-005.04. Upon reviewing the results of tap water and water quality parameter
monitoring by the system, both before and after the system installs optimal
corrosion control treatment, the Director must designate:
1. A minimum value or a range of values for
pH measured at each entry point to the distribution system;
2. A minimum pH value, measured in all tap
samples. Such value must be equal to or greater than 7.0, unless the Director
determines that meeting a pH level of 7.0 is not technologically feasible or is
not necessary for the system to optimize corrosion control;
3. If a corrosion inhibitor is used, a
minimum concentration or a range of concentrations for the inhibitor, measured
at each entry point to the distribution system and in all tap samples, that the
Director determines is necessary to form a passivating film on the interior
walls of the pipes of the distribution system;
4. If alkalinity is adjusted as part of
optimal corrosion control treatment, a minimum concentration or a range of
concentrations for alkalinity, measured at each entry point to the distribution
system and in all tap samples;
5.
If calcium carbonate stabilization is used as part of corrosion control, a
minimum concentration or a range of concentrations for calcium, measured in all
tap samples.
The values for the applicable water quality control
parameters listed above must be those that the Director determines to reflect
optimal corrosion control treatment for the system. The Director may designate
values for additional water quality control parameters determined by the
Director to reflect optimal corrosion control for the system. The Director must
notify the system in writing of these determinations and explain the basis for
its decisions.
005.07 Continued Operation and Monitoring
All systems optimizing corrosion control must continue to
operate and maintain optimal corrosion control treatment, including maintaining
water quality parameter values at or above minimum values or within ranges
designated by the Director under 179 NAC 12-005.06, in accordance with 179 NAC
12-005.07 for all samples collected under 179 NAC 12-010.04 through 12-010.06.
Compliance with the requirements of 179 NAC 12-005.07 must be determined every
six months, as specified under 179 NAC 12-010.04. A water system is out of
compliance with the requirements of 179 NAC 12-005.07 for a six-month period if
it has excursions for any Director-specified parameter on more than nine days
during the period. An excursion occurs whenever the daily value for one or more
of the water quality parameters measured at a sampling location is below the
minimum value or outside the range designated by the Director. Daily values are
calculated as follows. The Director has discretion to delete results of obvious
sampling errors from this calculation.
1. On days when more than one measurement for
the water quality parameter is collected at the sampling location, the daily
value must be the average of all results collected during the day regardless of
whether they are collected through continuous monitoring, grab sampling, or a
combination of both.
2. On days
when only one measurement for the water quality parameter is collected at the
sampling location, the daily value must be the result of that
measurement.
3. On days when no
measurement is collected for the water quality parameter at the sampling
location, the daily value must be the daily value calculated on the most recent
day on which the water quality parameter was measured at the sample
site.
005.08
Modification of Treatment Decisions Made by the Director
Upon its own initiative or in response to a request by a
water system or other interested party, the Director may modify his/her
determination of the optimal corrosion control treatment under 179 NAC
12-005.04 or optimal water quality control parameters under 179 NAC 12-005.06.
A request for modification by a system or other interested party must be in
writing, explain why the modification is appropriate, and provide supporting
documentation. The Director may modify his/her determination where s/he
concludes that such change is necessary to ensure that the system continues to
optimize corrosion control treatment. A revised determination must be made in
writing, set forth the new treatment requirements, explain the basis for the
Director's decision, and provide an implementation schedule for completing the
treatment modifications.
