| (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.
(B) The executive director shall designate optimal
corrosion control treatment. The executive director shall either approve
the corrosion control treatment option recommended by the system,
or designate alternative corrosion control treatment(s) from among
those listed in paragraph (1)(B)(i) of this subsection. When designating
optimal treatment the executive director shall consider the effects
that additional corrosion control treatment will have on water quality
parameters and on other water quality treatment processes. If the
executive director requests additional information, the water system
shall provide the information.
(C) Upon its own initiative or in response to a request
by a water system or other interested party, the executive director
may modify the determination of the optimal corrosion control treatment.
A request for modification by a system or other interested party shall
be in writing, explain why the modification is appropriate, and provide
supporting documentation. The executive director may modify the determination
when the change is necessary to ensure that the system continues to
optimize corrosion control treatment. A revised determination shall
be made in writing, set forth the new treatment requirements, explain
the basis for the decision, and provide an implementation schedule
for completing the treatment modifications.
(D) The executive director shall notify the system
of the decision on optimal corrosion control treatment in writing
and will provide the basis for this determination. The executive director
will review the study and designate optimal corrosion control treatment
and water quality parameters.
(i) For systems serving more than 50,000 customers,
optimal corrosion control treatment and OWQPs shall be designated
within six months of submittal.
(ii) For systems serving 3,300 to 50,000 customers,
optimal corrosion control treatment and OWQPs shall be designated
within 18 months of submittal.
(iii) For systems serving fewer than 3,300, optimal
corrosion control treatment and OWQPs shall be designated within 24
months of submittal.
(4) Installation of optimal corrosion control treatment.
A system shall perform corrosion control activities identified in
their approved corrosion control study. A system shall install optimal
corrosion control treatment within 24 months after the executive director
designates optimal corrosion control treatment and notifies the water
system. All applicable water systems shall operate optimal corrosion
control treatment in a manner that minimizes lead and copper concentrations
at users' taps while ensuring that the treatment does not cause the
system to violate any other drinking water standard.
(5) Operation of corrosion control treatment. All systems
optimizing corrosion control shall continue to operate and maintain
optimal corrosion control treatment, including operating within approved
OWQP ranges and complying with all other requirements of this section.
(A) The executive director shall evaluate the results
of all lead and copper tap samples and WQP samples submitted by the
water system to determine whether the corrosion control treatment
was properly installed and if the system is properly operating the
designated optimal corrosion control treatment.
(B) The system shall operate in such a manner as to
meet any requirements that the executive director determines appropriate
to ensure optimal corrosion control treatment is maintained.
(6) Small system activities cessation. A system serving
50,000 or fewer people that is required to perform corrosion control
activities because of an action level exceedance may cease the corrosion
control activities if it conducts two consecutive six-month lead and
copper monitoring rounds and meets the lead and copper action levels
based on the 90th percentile in both rounds.
Cont'd... |
