| (i) A system that operates within approved OWQP ranges
during three consecutive years of annual monitoring is eligible to
reduce the frequency of distribution WQP monitoring to once in every
third year. This sampling shall begin no later than the third calendar
year following the end of the monitoring period in which the third
consecutive year of monitoring occurs.
(ii) A system that demonstrates during two consecutive
six-month periods that the entry point 90th percentile lead level
is less than or equal to the PQL for lead in subsection (b)(3) of
this section, and that operates within approved OWQP ranges during
that time may reduce the frequency of distribution monitoring to once
every third year. This sampling shall begin no later than the third
calendar year following the end of the year in which the second consecutive
six-month period occurs.
(D) Return to routine WQP monitoring. The executive
director may return a system to monitoring at the routine frequency
and routine number of sample sites. Any water system on reduced monitoring
that fails to operate within the approved OWQP range for more than
nine days in any six-month monitoring period shall resume routine
WQP distribution system sampling in accordance with the number and
frequency requirements in paragraph (2) of this subsection. Any system
required to return to routine frequency for lead and copper tap sampling
under subsection (c)(2)(A)(ii) of this section shall also return to
routine WQP monitoring.
(E) Entry point WQP monitoring. Systems on reduced
WQP monitoring shall measure WQPs at every entry point to the distribution
system, except as provided under paragraph (6) of this subsection.
(6) Distribution system sampling for systems using
only groundwater. The executive director may allow a system using
only groundwater to perform WQP sampling required by paragraph (3),
(4), or (5) of this subsection to sample only at representative distribution
system sites, and to forego sampling at entry points. Prior to foregoing
entry point monitoring, the system shall provide written information
identifying the selected entry points and documentation, including
information on seasonal variability, sufficient to demonstrate that
the sites are representative of water quality and treatment conditions
throughout the system to the executive director for approval.
(f) Corrosion control. Systems may be required to perform
corrosion control studies to determine whether treatment is necessary
to reduce the corrosivity of the water. Systems may be required to
install optimal corrosion control treatment in order to control corrosion
in the system. The executive director may modify the designated corrosion
control treatment or parameters. A system's request for changes and
executive director response pursuant to modification shall be in writing.
(1) Corrosion control studies. Systems may be required
to perform corrosion control studies to determine whether treatment
is necessary to reduce the corrosivity of the water.
(A) Corrosion control studies applicability. Systems
that meet the conditions in this subparagraph are required to perform
corrosion control studies.
(i) Corrosion control studies for systems serving more
than 50,000 people. Systems serving more than 50,000 people are required
to conduct corrosion control studies unless the executive director
has determined that the system is currently deemed to have optimized
corrosion control, as defined in subsection (b)(5) of this section.
(I) Systems serving more than 50,000 people that exceed
either the lead or copper action level during any a reduced tap sampling
monitoring round must perform a corrosion control study within six
months.
(II) Systems serving more than 50,000 people that have
not been deemed at any previous time that exceed lead or copper action
levels must conduct a demonstration study as described in subparagraph
(C) of this paragraph.
(III) The corrosion control study must be conducted
and submitted within 12 months after the end of the monitoring period
in which the system exceeded the action level.
(ii) Corrosion control studies for systems serving
50,000 or fewer people. Any system serving 50,000 or fewer people
that exceeds the lead or copper action level must perform a corrosion
control study to identify optimal corrosion control treatment for
the system. The system must conduct the study within 12 months after
the end of the monitoring period in which the system exceeded the
action level.
(B) Scope of corrosion control study. A system required
to perform a corrosion control study shall include evaluation of treatment
methods and potential constraints to treatment.
(i) Corrosion control treatment methods. Any public
water system performing a corrosion control study shall evaluate the
effectiveness of each of the following treatments (or combinations
of treatments) to identify the optimal control treatment:
(I) alkalinity and pH adjustment;
(II) calcium hardness adjustment; and
(III) 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.
(ii) Potential constraints to corrosion control treatment
methods. The system shall identify all chemical or physical constraints
that limit or prohibit the use of a particular corrosion control treatment.
The system shall evaluate the effect of the chemicals used for corrosion
control treatment on other water quality treatment processes. The
system shall document treatment considerations with at least one of
the following:
(I) 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, or
(II) 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.
(C) Demonstration corrosion control study requirements.
The water system shall conduct this evaluation using pipe rig/loop
tests, metal coupon tests, or partial systems tests called a demonstration
study. The water system shall measure the parameters in this clause
in any tests conducted under this subparagraph before and after evaluating
the corrosion control treatments listed in subparagraph (B) of this
paragraph:
(i) lead;
(ii) copper;
(iii) pH;
(iv) alkalinity;
(v) calcium;
(vi) conductivity;
(vii) orthophosphate (when an inhibitor containing
a phosphate compound is used);
(viii) silicate (when an inhibitor containing a silicate
compound is used); and
(ix) water temperature.
(D) Desk-top corrosion control study requirements.
A desk-top corrosion control study shall recommend treatment and OWQPs
based on data for treatments in documented analogous systems called
a desk-top study. Analogous system means a system of similar size,
water chemistry, and distribution system configuration. The water
system shall evaluate each of the corrosion control treatments in
subparagraph (B)(i) of this paragraph.
(2) Setting approved OWQP ranges based on corrosion
control study data. On the basis of the corrosion control study evaluation,
the water system shall recommend to the executive director, in writing,
an OWQP range based on normal system operating conditions. Systems
must recommend OWQPs consistent with subsection (b)(4) of this section.
The executive director will review the study and designate OWQPs.
The executive director shall designate OWQP ranges based on the results
of lead, copper, and WQP monitoring by the system, both before and
after the system installs optimal corrosion control treatment. The
executive director may designate values for additional water quality
control parameters determined to reflect optimal corrosion control
for the system. The executive director shall notify the system in
writing of these determinations and will provide the basis for the
decision.
(3) Optimal corrosion control treatment designation.
A system exceeding the action level for lead or copper based on the
90th percentile level shall submit recommendations for optimal corrosion
control treatment within six months after the end of the monitoring
period during which it exceeds one of the action levels. The executive
director shall designate the optimal corrosion control treatment method.
(A) On the basis of the corrosion control study in
paragraph (1) of this subsection, lead and copper tap sampling, and
WQP sampling the water system shall recommend to the executive director,
in writing, the treatment option that constitutes optimum corrosion
control. The system shall submit all corrosion control data and shall
provide sufficient documentation as required by the executive director
to establish the validity of the evaluation procedure.
Cont'd... |
