WAC 246-290-664
Monitoring for filtered systems. (1)
Source coliform monitoring.
(a) The purveyor shall ensure that source water samples
of each surface or GWI source are:
(i) Collected before the first point of disinfectant
application and before coagulant chemical addition; 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 of 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.
(c) With written approval from the department, purveyors
of filtered water systems serving less than ten thousand
people may collect twenty-six consecutive monthly fecal
coliform samples instead of collecting E. coli samples every
two weeks for twelve months as specified in 40 CFR 141.701
(a)(3)(i). The fecal coliform levels that will trigger
Cryptosporidium monitoring will be the same as the E. coli
levels specified in 40 CFR 141.701 (a)(4)(i), (ii), or (iv).
(2) Source turbidity monitoring.
(a) The purveyor using conventional, direct, or in-line
filtration shall measure source turbidity at least once per
day on a representative sample collected before disinfection
and coagulant addition.
(b) Grab sampling or continuous turbidity monitoring and
recording may be used to meet the requirement specified in (a)
of this subsection.
(c) Purveyors using continuous turbidity monitoring shall
record continuous turbidity measurements at equal intervals,
at least every four hours, in accordance with a
department-approved sampling schedule.
(d) Purveyors using an approved alternative
filtration technology may be required to monitor source water
turbidity at least once per day on a representative sample as
determined by the department.
(3) Filtered water turbidity monitoring.
(a) The purveyor using direct, conventional, or in-line
filtration shall:
(i) Continuously monitor turbidity on representative
samples from each individual filter unit and from the system's
combined filter effluent, prior to clearwell storage;
(ii) For systems serving at least ten thousand people,
record continuous turbidity measurements from each individual
filter unit at equal intervals of at least every fifteen
minutes, and for all systems, from the combined filter
effluent at equal intervals of at least every four hours, in
accordance with a department-approved sampling schedule;
(iii) Beginning January 14, 2005, systems serving less
than ten thousand people shall record continuous turbidity
measurements from each individual filter unit at equal
intervals of at least every fifteen minutes;
(iv) Systems serving less than ten thousand people and
consisting of two or fewer filters may record continuous
turbidity measurements from the combined filter effluent at
equal intervals of at least fifteen minutes in lieu of
recording individual filter turbidity measurements; and
(v) Conduct monitoring in accordance with the analytical
techniques under WAC 246-290-638.
(b) The purveyor using slow sand or diatomaceous earth
filtration shall:
(i) Continuously monitor turbidity on representative
samples from each individual filter unit and from the system's
combined filter effluent, prior to clearwell storage;
(ii) Record continuous turbidity measurements from the
combined filter effluent at equal intervals of at least every
four hours in accordance with a department-approved sampling
schedule; and
(iii) Conduct monitoring in accordance with the
analytical techniques under WAC 246-290-638.
(c) Purveyors using an alternative
filtration technology approved under WAC 246-290-676 shall
provide monitoring in accordance with the technology-specific
approval conditions determined by the department.
(d) Purveyors using slow sand filtration or an alternative filtration technology may reduce
filtered water turbidity monitoring to one grab sample per day
with department approval. Reduced turbidity
monitoring shall be allowed only where the purveyor
demonstrates to the department's satisfaction that a reduction
in monitoring will not endanger the health of consumers served
by the water system.
(4) Monitoring the level of inactivation and removal.
(a) Each day the system is in operation, the purveyor
shall determine the total level of inactivation and removal of
Giardia lamblia cysts, viruses, and Cryptosporidium oocysts
achieved.
(b) The purveyor shall determine the total level of
inactivation and removal based on:
(i) Giardia lamblia cyst, Cryptosporidium oocyst, and
virus removal credit granted by the department for filtration;
and
(ii) Level of inactivation of Giardia lamblia cysts and
viruses achieved through disinfection.
(c) At least once per day, purveyors shall monitor the
following to determine the level of inactivation 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.
(d) Each day during peak hourly flow (based on historical
information), 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 shall be located before or at the first
consumer.
(e) The department may reduce CT monitoring requirements
for purveyors that demonstrate to the department's
satisfaction that the required levels of inactivation are
consistently exceeded. Reduced CT monitoring shall only be
allowed where the purveyor demonstrates to the department's
satisfaction that a reduction in monitoring will not endanger
the health of consumers.
(5) Monitoring the residual disinfectant concentration
entering the distribution system.
(a) Systems serving more than thirty-three hundred people
per month.
(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 on-line within five working days
following failure.
(b) Systems serving thirty-three hundred or less people
per month.
(i) The purveyor shall collect grab samples or use
continuous monitoring and recording to measure the residual
disinfectant concentration entering the distribution system.
(ii) Purveyors of community systems 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;
and
(C) The remaining samples evenly spaced over the time the
system is disinfecting water that will be delivered to the
public.
(iii) Purveyors of noncommunity systems choosing to take
grab samples shall collect samples for disinfectant residual
concentration entering the distribution system as directed by
the department.
(iv) When grab samples are collected and the residual
disinfectant concentration at the entry to distribution falls
below 0.2 mg/L, purveyors shall collect a grab sample every
four hours until the residual disinfectant concentration is
0.2 mg/L or more.
(6) Monitoring residual disinfectant concentrations
within the distribution system.
(a) The purveyor shall measure the residual disinfectant
concentration at representative points within the distribution
system on a daily basis or as otherwise approved by the
department.
(b) 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) or 246-290-320(2).
(c) The purveyor may measure HPC within the distribution
system in lieu of measuring the residual disinfectant
concentration under this subsection.
[Statutory Authority: RCW 70.119A.180 and 43.20.050. 08-03-061, § 246-290-664, filed 1/14/08, effective 2/14/08. Statutory Authority: RCW 43.20.050 and 70.119A.080.
04-04-056, § 246-290-664, filed 1/30/04, effective 3/1/04.
Statutory Authority: RCW 43.20.050 (2) and (3) and70.119A.080
. 03-08-037, § 246-290-664, filed 3/27/03,
effective 4/27/03. Statutory Authority: RCW 43.02.050
[43.20.050]. 99-07-021, § 246-290-664, filed 3/9/99,
effective 4/9/99. Statutory Authority: RCW 43.20.050.
94-14-001, § 246-290-664, filed 6/22/94, effective 7/23/94;
93-08-011 (Order 352B), § 246-290-664, filed 3/25/93,
effective 4/25/93.]