Current through Register Vol. 24-18, September 15, 2024
(1) No
portion of a public water system containing potable water shall be put into
service, nor shall service be resumed until the facility has been effectively
disinfected.
(a) In cases of new
construction, drinking water shall not be furnished to the consumer until
satisfactory bacteriological samples have been analyzed by a laboratory
certified by the state;
(b) In
cases of existing water mains, when the integrity of the main is lost resulting
in a significant loss of pressure that places the main at risk to
contamination, the purveyor shall use standard industry practices to ensure
adequate and safe water quality prior to the return of the line to service,
including at least one of the following:
(i)
Flushing;
(ii) Disinfection;
or
(iii) Bacteriological
sampling.
(c) If a
cross-connection is confirmed, the purveyor shall satisfy the reporting
requirements as described under WAC
246-290-490(8).
(2) The procedure used for
disinfection shall conform to standards published by the American Water Works
Association, or other industry standards acceptable to the
department.
(3) The purveyor of a
system using surface water or GWI shall meet disinfection requirements
specified in Part 6 of this chapter.
(4) If the department determines that any of
the following conditions apply, the purveyor shall provide continuous
disinfection of the source and meet the requirements under subsection (6) of
this section :
(a) A groundwater source is in
hydraulic connection to surface water under WAC
246-290-640(4);
(b) A history of unsatisfactory total
coliform sampling results for a groundwater source;
(c) A microbial contaminant threat within a
groundwater source sanitary control area as defined in WAC
246-290-135;
(d) A microbial contaminant threat to a
source, as documented in a susceptibility assessment, a sanitary survey, or a
special purpose investigation which also includes, but is not limited to, one
or more of the following conditions:
(i) A
poorly constructed source;
(ii) An
inadequate surface seal;
(iii) High
groundwater;
(iv) Lack of confining
layers in the aquifer;
(v) A
shallow well source, with the first open interval fifty feet or less from the
ground surface at the wellhead;
(vi) A drilled well in fractured bedrock;
or
(vii) A source at risk of
flooding.
(e)
Desalination of a seawater water source by reverse osmosis.
(5) If the department determines
that any of the following conditions apply, the purveyor shall provide
continuous disinfection of the distribution system and meet the requirements
under subsection (7) of this section:
(a)
E. coli MCL violations;
(b) Level 1 or level 2 assessment treatment
technique triggers;
(c) Failure to
complete level 1 or level 2 assessments as required under WAC
246-290-320(2)(b);
(d) Failure to complete corrective actions
required under WAC
246-290-320(2)(d);
or
(e) Facility failures that
threaten to degrade water quality in the distribution system.
(6) If disinfection is required
under subsection (4) of this section, the following requirements must be met:
(a) Provide any combination of free chlorine
residual concentration (C), measured in mg/L at or before the first customer
and contact time (T), measured in minutes between the location of chlorine
treatment and residual measurement, that result in a CT product (C x T) of
greater than or equal to six without exceeding the chlorine MRDL in WAC
246-290-310(5).
(b) The department may require the purveyor
to provide longer contact times, higher chlorine residuals, or additional
treatment to protect the health of consumers served by the water
system.
(c) To demonstrate the
required level of treatment is maintained, the purveyor shall:
(i) Monitor the residual disinfectant
concentration at the point of entry to the distribution system, or at a
department-approved location, at least once per day, five days per week or each
day that water is supplied by the treatment plant if it operates less than
daily;
(ii) Identify the number of
days each month that the treatment process failed to meet the disinfection
treatment requirement in this subsection; and
(iii) Submit monthly water treatment reports
to the department using a department-approved form by the tenth day of the
following month.
(d) All
analyses required in this subsection shall be conducted in accordance with an
EPA approved method. A diethyl-p-phenylenediamine (DPD) colorimetric field test
kit relying on a visual color comparison to a visual standard may not be used
by a purveyor to comply with the requirements of this subsection.
(e) The department may require the purveyor
to monitor the residual disinfectant concentration each calendar day water is
supplied to the distribution system if the department considers source
treatment operation unreliable.
(f)
The department may require the use of continuous residual analyzers and
recorders to assure adequate monitoring of residual concentrations.
(7) A purveyor that adds free
chlorine, total chlorine, combined chlorine, or chlorine dioxide to the
distribution system on a continuous basis shall:
(a) Monitor residual disinfectant
concentration at:
(i) Representative points in
the distribution system at least once per day, five days per week, unless upon
written request, the department approves less frequent monitoring;
and
(ii) The same time and location
of routine and repeat coliform sample collection.
(b) Maintain a detectable residual
disinfectant concentration in all active parts of the distribution system,
unless the department approves a written request to use a lower value. At a
minimum, the request to use a lower value must identify the instrument used to
measure the residual disinfectant concentration and include the manufacturer's
documentation of the instrument's accuracy to measure the lower
value.
(c) Submit monthly water
treatment reports to the department using a department-approved form by the
tenth day of the following month.
(d) Conduct all analyses required in this
subsection :
(i) In accordance with an EPA
approved method; or
(ii) Using a
diethyl-p-phenylenediamine (DPD) colori-metric field test kit unless not
allowed by the department.
(e) Colorimetric test strips may not be used
by a purveyor to comply with the residual disinfectant concentration monitoring
requirements of this subsection.
(f) The department may require the use of
continuous residual analyzers and recorders to assure adequate monitoring of
residual concentrations.
(g) The
department may require the purveyor to provide higher disinfectant residuals,
or additional treatment to protect the health of consumers served by the water
system.
(h) If a chemical
disinfectant is added to the distribution system for purposes other than
continuous disinfection and the treatment purposes and procedures are
identified in a treatment design approved under WAC
246-290-110 and
246-290-120, the system shall be
exempt from the requirements of this section.
(8) Violations.
(a) Failure to provide treatment that meets
the applicable requirements of subsection (6) or (7) of this section in two or
more calendar days per month in which residual disinfectant concentration
monitoring was conducted is a treatment technique violation;
(b) Failure to perform monitoring that meets
the applicable requirements of subsection (6) or (7) of this section is a
monitoring violation; or
(c)
Failure to submit a monthly water treatment plant report to the department
using a department-approved form by the tenth day of the following month in
accordance with the requirements of subsection (6) or (7) of this section is a
reporting violation.
(9)
Purveyors that add free chlorine, total chlorine, combined chlorine, or
chlorine dioxide to a source or the distribution system for any reason shall,
in addition to any other applicable monitoring requirements of this section,
measure residual disinfectant concentrations in samples collected at the same
time and location that routine or repeat coliform samples are collected, unless
the department determines that more frequent monitoring is necessary to protect
public health.
Statutory Authority:
RCW
43.20.050 and
70.119A.080. 10-20-068, §
246-290-451, filed 9/29/10, effective 11/1/10. Statutory Authority:
RCW
43.20.050(2) and (3) and
70.119A.080. 03-08-037, §
246-290-451, filed 3/27/03, effective 4/27/03. Statutory Authority: RCW
43.02.050 [43.20.050]. 99-07-021, § 246-290-451, filed 3/9/99, effective
4/9/99.
