South Carolina Code of Regulations
Chapter 61 - DEPARTMENT OF HEALTH AND ENVIRONMENTAL CONTROL
Subchapter 61-58.11 - Control of Lead and Copper
Section 61-58.11.I - Monitoring requirements for Water Quality Parameters
Universal Citation: SC Code Regs 61-58.11.I
Current through Register Vol. 48, No. 9, September 27, 2024
All large water systems, and all small and medium-size systems that exceed the lead or copper action level, and all small and medium-size water systems with corrosion control treatment that exceed the lead trigger level must monitor water quality parameters in addition to lead and copper in accordance with this section.
(1) General Requirements
(a) Sample Collection
Methods
(i) Tap samples shall be
representative of water quality throughout the distribution system taking into
account the number of persons served, the different sources of water, the
different treatment methods employed by the system, and seasonal variability.
Tap sampling under this section is not required to be conducted at taps
targeted for lead and copper sampling under R.61-58.11.H(1).
Sites selected for tap samples under this section must be included in the site
sample plan specified under R.61-58.11.H(1)(a).
The site sample plan must be updated prior to changes to the sampling
locations. [Note: Systems may find it convenient to conduct tap sampling for
water quality parameters at sites used for coliform sampling under
R.61-58.5.G if they also meet the
requirements of this section.]
(ii)
Samples collected at the entry point(s) to the distribution system must be from
locations representative of each source after treatment. If a system draws
water from more than one source and the sources are combined before
distribution, the system must sample at an entry point to the distribution
system during periods of normal operating conditions (i.e., when water is
representative of all sources being used).
(b) Number of Samples
(i) Systems must collect two (2) tap samples
for applicable water quality parameters during each monitoring period specified
under paragraphs (2) through (5) of this section from the minimum number of
sites listed in table 1 to this paragraph (1)(b)(i). Systems that add sites as
a result of the "find-and-fix'' requirements in R.61-58.11.D(10)
must collect tap samples for applicable water quality parameters during each
monitoring period under paragraphs (2) through (5) of this section and must
sample from that adjusted minimum number of sites. Systems are not required to
add sites if they are monitoring at least twice the minimum number of sites
list in table 1 to this paragraph (1)(b)(i).
Table 1 To Paragraph (1)(b)(i)
|
System Size (# People Served) |
# Of Sites For Water Quality Parameters |
|
>100,000 |
25 |
|
10,001 to 100,000 |
10 |
|
3,301 to 10,000 |
3 |
|
501 to 3,300 |
2 |
|
101 to 500 |
1 |
|
<=100 |
1 |
(ii)
(A) Except as provided in paragraph (3)(b) of
this section, water systems without corrosion control treatment must collect
two (2) samples for each applicable water quality parameter at each entry point
to the distribution system during each monitoring period specified in paragraph
(2) of this section. During each monitoring period specified in paragraphs (3)
through (5) of this section, water systems must collect one (1) sample for each
applicable water quality parameter at each entry point to the distribution
system.
(B) During each monitoring
period specified in paragraphs (3) through (5) of the section, water systems
with corrosion control treatment must continue to collect one (1) sample for
each applicable water quality parameter at each entry point to the distribution
system no less frequently than once every two (2) weeks.
(2) Initial Sampling for Water Systems-
Any large water system without corrosion control treatment must monitor for water quality parameters as specified in paragraphs (2)(a) and (b) of this section during the first two (2) six (6)-month tap sampling monitoring periods beginning no later than January 1 of the calendar year after the system either becomes a large water system, or fails to maintain their 90th percentile for lead below the practical quantitation limit (PQL) for lead. Any medium or small system that exceeds the lead or copper action level and any system with corrosion control treatment for which the Department has not designated optimal water quality parameters (OWQPs) that exceeds the lead trigger level shall monitor for water quality parameters as specified in paragraphs (2)(a) and (b) of this section for two (2) consecutive six (6)-month periods beginning the month immediately following the end of the tap sampling period in which the exceedance occurred.
(a) At taps:
(i) pH;
(ii) Alkalinity; and
(b) At each entry point to the distribution
system: all of the applicable parameters listed in paragraph (2)(a) of this
section.
(3) Monitoring After Installation of Optimal Corrosion Control or Re-optimized Corrosion Control Treatment.
(a) Any system that
installs or modifies corrosion control treatment pursuant to R.61-58.11.C(4)(e) or
(5)(e) and is required to monitor pursuant
R.61-58.11.C(4)(f) or
(5)(f) must monitor the parameters identified
in paragraphs (3)(a)(i) and (ii) of this section every six (6) months at the
locations and frequencies specified in paragraphs (3)(a)(i) and (ii) of this
section until the Department specifies new water quality parameter values for
optimal corrosion control pursuant to paragraph (4) of this section. Water
systems must collect these samples evenly throughout the six (6)-month
monitoring period so as to reflect seasonal variability.
(i) At taps, two (2) samples each for:
(A) pH;
(B) Alkalinity;
(C) Orthophosphate, when an inhibitor
containing an orthophosphate compound is used;
(D) Silica, when an inhibitor containing a
silicate compound is used.
(ii) Except as provided in paragraph
(3)(a)(iii) of this section, at each entry point to the distribution system, at
least one sample no less frequently than every two weeks (biweekly) for:
(A) pH;
(B) When alkalinity is adjusted as part of
optimal corrosion control, a reading of the dosage rate of the chemical used to
adjust alkalinity, and the alkalinity concentration; and
(C) When a corrosion inhibitor is used as
part of optimal corrosion control, a reading of the dosage rate of the
inhibitor used, and the concentration of orthophosphate or silica (whichever is
applicable).
(iii) Any
groundwater system can limit entry point sampling described in paragraph
(3)(a)(ii) of this section to those entry points that are representative of
water quality and treatment conditions throughout the system. If water from
untreated groundwater sources mixes with water from treated groundwater
sources, the system must monitor for water quality parameters both at
representative entry points receiving treatment and representative entry points
receiving no treatment. Prior to the start of any monitoring under this
paragraph (3)(a)(iii), the water system must provide to the Department 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.
(b) The
Department has the discretion to require small and medium-size systems with
treatment for which the Department has not designated OWQPs that exceed the
lead trigger level but not the lead and copper action levels to conduct water
quality parameter monitoring as described in paragraph (3)(a) of this section
or the Department can develop its own water quality control parameter
monitoring structure for these systems.
(4) Monitoring After the Department Specifies Water Quality Parameter Values for Optimal Corrosion Control
(a) After the Department specifies the values
for applicable water quality parameters reflecting optimal corrosion control
treatment under R.61-58.11.D(6),
systems must monitor for the specified optimal water quality parameters during
six (6)-month periods that begin on either January 1 or July 1. Such monitoring
must be spaced evenly throughout the six (6)-month monitoring period so as to
reflect seasonal variability and be consistent with the structure specified in
paragraphs (3)(a)(i) through (iii) of this section.
(i) All large systems must measure the
applicable water quality parameters specified by the Department and determine
compliance with the requirements of R.61-58.11.D(7)
every six (6) months with the first six (6)-month period to begin on either
January 1 or July 1, whichever comes first, after the Department specifies the
optimal values under R.61-58.11.D(6).
(ii) Any small or medium-size water system
that exceeds an action level must begin monitoring during the six (6)-month
period immediately following the tap sampling monitoring period in which the
exceedance occurs and continue monitoring until the water system no longer
exceeds the lead and copper action levels and meets the optimal water quality
control parameters in two (2) consecutive six (6)-month tap sampling monitoring
periods under R.61-58.11.H(4)(c).
For any such small and medium-size system that is subject to a reduced
monitoring frequency pursuant to R.61-58.11.H(4)(d)
at the time of the action level exceedance, the start of the applicable six
(6)-month monitoring period under this paragraph must coincide with the start
of the applicable tap sampling monitoring period under R.61-58.11.H(4)(d).
(iii) Compliance with Department-designated
optimal water quality parameter values must be determined as specified under
R.61-58.11.D(7).
(b) Any small or medium-size
system that exceeds the lead trigger level, but not the lead and copper action
levels for which the Department has set optimal water quality control
parameters must monitor as specified in paragraph (4)(a) of this section every
six (6) months, until the system no longer exceeds the lead trigger level in
two (2) consecutive tap sampling monitoring periods.
(c) The Department has the discretion to
continue to require systems described in paragraph (4)(b) of this section to
monitor optimal water quality control parameters.
(5) Reduced Monitoring
(a) Any large water system that maintains the
range of values for the water quality parameters reflecting optimal corrosion
control treatment specified by the Department under R.61-58.11.D(6) and
does not exceed the lead trigger level during each of two (2) consecutive six
(6)-month monitoring periods under paragraph (4) of this section must continue
monitoring at the entry point(s) to the distribution system as specified in
paragraph (3)(a)(ii) of this section. Such system may collect two (2) tap
samples for applicable water quality parameters from the following reduced
number of sites during each six (6) month monitoring period. Water systems must
collect these samples evenly throughout the six (6)-month monitoring period so
as to reflect seasonal variability.
|
Reduced # Of Sites System Size (# People Served) |
For Water Quality Parameters |
|
>100,000 |
10 |
|
10,001 to 100,000 |
7 |
|
3,301 to 10,000 |
3 |
|
501 to 3,300 |
2 |
|
101 to 500 |
1 |
|
<=100 |
1 |
(b)
(i) Any water system that maintains the range
of values for the water quality parameters reflecting optimal corrosion control
treatment specified by the Department under R.61-58.11.D(6) and
does not exceed the lead trigger level or copper action level during three (3)
consecutive years of monitoring may reduce the frequency with which it collects
the number of tap samples for applicable water quality parameters specified in
this paragraph (5)(a) of this section from every six (6) months to annually.
This sampling begins during the calendar year immediately following the end of
the monitoring period in which the third consecutive year of six (6)-month
monitoring occurs.
(ii) A water
system may reduce the frequency with which it collects tap samples for
applicable water quality parameters specified in paragraph (5)(a) of this
section to every year if it demonstrates during two (2) consecutive monitoring
periods that its tap water lead level at the 90th percentile is less than or
equal to the PQL for lead of 0.005 mg/L, that its tap water copper level at the
90th percentile is less than or equal to 0.65 mg/L in R.61-58.11.B(1)(b),
and that it also has maintained the range of values for the water quality
parameters reflecting optimal corrosion control treatment specified by the
Department under R.61-58.11.D(6).
(c) A water system that conducts
sampling annually must collect these samples evenly throughout the year so as
to reflect seasonal variability.
(d) Any water system subject to reduced
monitoring frequency that fails to operate at or above the minimum value or
within the range of values for the water quality parameters specified by the
Department under R.61-58.11.D(6),
for more than nine (9) days in any six (6) month period specified in
R.61-58.11.D(7),
must resume distribution system tap water sampling in accordance with the
number and frequency requirements in paragraph (4) of this section. Such a
system may resume annual monitoring for water quality parameters at the tap at
the reduced number of sites specified in paragraph (5)(a) of this section after
it has completed two (2) subsequent consecutive six (6) month rounds of
monitoring that meet the criteria of paragraph (5)(a) of this section and/or
may resume annual monitoring for water quality parameters at the tap at the
reduced number of sites after it demonstrates through subsequent rounds of
monitoring that it meets the criteria of either paragraph (5)(b)(i) or
(5)(b)(ii) of this section.
(6) Additional Monitoring by Systems
The results of any monitoring conducted in addition to the minimum requirements of this section must be considered by the water system and the Department in making any determinations (i.e., determining concentrations of water quality parameters) under this section or R.61-58.11.D.
(7) Additional Sites Added from Find-and-fix.
Any water system that conducts water quality parameter monitoring at additional sites through the "find-and-fix'' provisions pursuant to R.61-58.11.D(10) must add those sites to the minimum number of sites specified under paragraphs (1) through (5) of this section unless the system is monitoring at least twice the minimum number of sites.
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