Washington Administrative Code
Title 246 - Health, Department of
WATER SYSTEMS
Chapter 246-290 - Group A public water supplies
Part 6 - SURFACE WATER TREATMENT
Subpart D - Requirements for Other Unfiltered Systems
Section 246-290-694 - Monitoring for unfiltered systems
Universal Citation: WA Admin Code 246-290-694
Current through Register Vol. 24-18, September 15, 2024
(1) Source coliform monitoring for systems without a limited alternative to filtration.
(a) The purveyor shall ensure that source
water samples of each surface or GWI source are representative and:
(i) Collected before the first point of
disinfectant application; and
(ii)
Analyzed for fecal coliform density in accordance with methods acceptable to
the department.
(b) The
purveyor shall ensure source samples are collected for fecal coliform analysis
each week the system serves water to the public based on the following
schedule:
| Population Served | Minimum Number/week* |
| 25 - 500 | 1 |
| 501 - 3,300 | 2 |
| 3,301 - 10,000 | 3 |
| 10,001 - 25,000 | 4 |
| >25,000 | 5 |
*Must be taken on separate days.
(c) Each day the system serves water to the
public and the turbidity of the source water exceeds 1.0 NTU, the purveyor
shall ensure one representative source water sample is collected before the
first point of disinfectant application and analyzed for fecal coliform
density. This sample shall count toward the weekly source coliform sampling
requirement.
(d) The purveyor using
a surface water or GWI source and that meets the criteria to remain unfiltered
under WAC
246-290-690, shall collect at
least one routine sample near the first service connection each day the
turbidity level of the source water, measured as specified under WAC
246-290-694, exceeds 1 NTU. This
sample must be analyzed for the presence of total coliform. When one or more
turbidity measurements in any day exceed 1 NTU, the system must collect this
coliform sample within twenty-four hours of the first exceedance, unless the
department determines that the system, for logistical reasons outside the
system's control, cannot have the sample analyzed within thirty hours of
collection. Sample results from this coliform monitoring must be included in
determining compliance with the E. coli MCL under WAC
246-290-310(2)(b)
and exceeding treatment technique triggers
under WAC
246-290-320(2)(a).
(e) A purveyor shall not be considered in
violation of (c) of this subsection, if the purveyor demonstrates to the
department's satisfaction that, for valid logistical reasons outside the
purveyor's control, the additional fecal coliform sample could not be analyzed
within a time frame acceptable to the department.
(2) Source coliform monitoring for systems with a limited alternative to filtration.
(a)
The purveyor shall ensure that source water samples of each surface or GWI
source are:
(i) Collected before the first
point of primary disinfection; and
(ii) Analyzed for fecal coliform density in
accordance with methods acceptable to the department.
(b) At a minimum, the purveyor shall ensure
source samples are collected for fecal coliform analysis at a frequency equal
to ten percent the number of routine coliform samples collected within the
distribution system each month under WAC
246-290-300, or once per calendar
month, whichever is greater, up to a maximum of one sample per day.
(3) Coliform monitoring at entry to distribution for systems without a limited alternative to filtration.
(a) The purveyor shall collect and have
analyzed one coliform sample at the entry point to the distribution system each
day that a routine or repeat coliform sample is collected within the
distribution system under WAC
246-290-300(3)(e) through
(g).
(b) The purveyor shall use the results of the
coliform monitoring at entry to distribution along with inactivation ratio
monitoring results to demonstrate the adequacy of source treatment.
(4) Source turbidity monitoring for systems without a limited alternative to filtration.
(a) The purveyor shall continuously monitor
and record turbidity:
(i) On representative
source water samples before the first point of primary disinfectant
application; and
(ii) In accordance
with the analytical techniques in WAC
246-290-638.
(b) If source water turbidity is not the same
as the turbidity of water delivered to consumers, the purveyor shall
continuously monitor and record turbidity of water delivered.
(5) Source turbidity monitoring for systems with a limited alternative to filtration. The purveyor shall:
(a) Continuously monitor turbidity on
representative source samples before the first point of primary disinfection
application;
(b) Record continuous
turbidity measurements at equal intervals, of at least four hours, in
accordance with a department-approved sampling schedule; and
(c) Conduct monitoring in accordance with the
analytical techniques under WAC
246-290-638.
(6) Monitoring the level of inactivation.
(a) Each day the system is in operation, the
purveyor shall determine the total level of inactivation of Giardia
lam-blia cysts, viruses, and, if providing a limited alternative to
filtration, any other pathogenic organisms of health concern including
Cryptosporidium oocysts, achieved through
disinfection.
(b) At least once per
day, the purveyor shall monitor the following parameters to determine the total
inactivation ratio achieved through disinfection:
(i) Temperature of the disinfected water at
each residual disinfectant concentration sampling point used for CT
calculations; and
(ii) If using
chlorine, pH of the disinfected water at each chlorine residual disinfectant
concentration sampling point used for CT calculations.
(c) Each day during peak hourly flow, the
purveyor shall:
(i) Determine disinfectant
contact time, T, to the point at which C is measured; and
(ii) Measure the residual disinfectant
concentration, C, of the water at the point for which T is calculated. The C
measurement point must be before or at the first consumer.
(7) Monitoring the residual disinfectant concentration entering the distribution system for either unfiltered systems, or systems using a limited alternative to filtration.
(a) Systems serving more than thirty-three
hundred people.
(i) The purveyor shall
continuously monitor and record the residual disinfectant concentration of
water entering the distribution system and report the lowest value each
day.
(ii) If the continuous
monitoring equipment fails, the purveyor shall measure the residual
disinfectant concentration on grab samples collected at least every four hours
at the entry to the distribution system while the equipment is being repaired
or replaced. The purveyor shall have continuous monitoring equipment back
online within five working days following failure.
(b) Systems serving thirty-three hundred or
less people.
(i) The purveyor shall collect
grab samples or use continuous monitoring and recording to measure the residual
disinfectant concentration entering the distribution system.
(ii) A purveyor choosing to take grab samples
shall collect:
(A) Samples at the following
minimum frequencies:
| Population Served | Number/day |
| 25 - 500 | 1 |
| 501 - 1,000 | 2 |
| 1,001 - 2,500 | 3 |
| 2,501 - 3,300 | 4 |
(B) At least one of the grab samples at peak
hourly flow based on historical flows for the system; and
(C) The remaining sample or samples at
intervals evenly spaced over the time the system is disinfecting water that
will be delivered to the public.
(iii) When grab samples are collected and the
residual disinfectant concentration at the entry to distribution falls below
0.2 mg/L, the purveyor shall collect a grab sample every four hours until the
residual disinfectant concentration is 0.2 mg/L or more.
(8) Monitoring residual disinfectant concentration within the distribution system for either unfiltered systems, or systems using a limited alternative to filtration.
(a) The purveyor shall measure the residual
disinfectant concentration within the distribution system at the same time and
location that a routine or repeat coliform sample is collected under WAC
246-290-300(3)(e) through
(g) or once per day, whichever is
greater.
(b) The purveyor of a
system that purchases completely treated surface or GWI water as determined by
the department shall comply with the requirements of (a) of this subsection or
as otherwise directed by the department under WAC
246-290-300(2).
At a minimum, the purveyor shall measure the residual disinfectant
concentration within the distribution system at the same time and location that
a routine or repeat coliform sample is collected under WAC
246-290-300(3)(e) through
(g).
(c) The purveyor may measure HPC within the
distribution system in lieu of measuring the residual disinfectant
concentration under this subsection.
Statutory Authority: RCW 43.20.050. 09-21-045, § 246-290-694, filed 10/13/09, effective 1/4/10. Statutory Authority: RCW 70.119A.180 and 43.20.050. 08-03-061, § 246-290-694, filed 1/14/08, effective 2/14/08. Statutory Authority: RCW 43.20.050(2) and (3) and 70.119A.080. 03-08-037, § 246-290-694, filed 3/27/03, effective 4/27/03. Statutory Authority: RCW 43.02.050 [43.20.050]. 99-07-021, § 246-290-694, filed 3/9/99, effective 4/9/99. Statutory Authority: RCW 43.20.050. 94-14-001, § 246-290-694, filed 6/22/94, effective 7/23/94; 93-08-011 (Order 352B), § 246-290-694, filed 3/25/93, effective 4/25/93.
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