246-290-692  <<  246-290-694 >>   246-290-696

Monitoring for unfiltered systems.

(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 lamblia 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 and 70.119A.080. WSR 17-01-062, § 246-290-694, filed 12/14/16, effective 1/14/17. Statutory Authority: RCW 43.20.050. WSR 09-21-045, § 246-290-694, filed 10/13/09, effective 1/4/10. Statutory Authority: RCW 70.119A.180 and 43.20.050. WSR 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. WSR 03-08-037, § 246-290-694, filed 3/27/03, effective 4/27/03. Statutory Authority: RCW 43.02.050 [43.20.050]. WSR 99-07-021, § 246-290-694, filed 3/9/99, effective 4/9/99. Statutory Authority: RCW 43.20.050. WSR 94-14-001, § 246-290-694, filed 6/22/94, effective 7/23/94; WSR 93-08-011 (Order 352B), § 246-290-694, filed 3/25/93, effective 4/25/93.]
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