Current through Register Vol. 24-18, September 15, 2024
(1) The purveyor shall calculate T at peak
hourly flow for each surface or GWI source.
(2) For pipelines, the purveyor shall
calculate T by dividing the internal volume of the pipe by the peak hourly flow
rate through that pipe.
(3) For all
other system components used for inactivation of Giardia
lamblia cysts, viruses, and other microorganisms of public health
concern, the purveyor shall use tracer studies or empirical methods to
determine T.
(4) The purveyor shall
use the T10 value determined by tracer studies or other methods acceptable to
the department as T in all CT calculations.
(5) Tracer studies.
(a) The purveyor shall conduct field tracer
studies on all system components with configurations (geometry and/or baffling)
for which analogous contact times are not documented.
(b) Before conducting tracer studies, the
purveyor shall obtain the department's approval of a tracer study plan. The
plan shall identify at a minimum:
(i) How the
purveyor will conduct the study;
(ii) The tracer material to be
used;
(iii) Flow rates to be used;
and
(iv) The names, titles, and
qualifications of the persons conducting the study.
(c) A professional engineer registered in the
state of Washington shall direct the conduct of all tracer studies.
(d) Tracer studies shall be conducted in
accordance with good engineering practices using methods acceptable to the
department such as those described in department guidance on surface water
treatment.
(e) The department may
require the purveyor to conduct additional tracer studies when:
(i) Modifications impacting flow distribution
or T are made; or
(ii) Increases in
flow exceed the conditions of the previous tracer studies.
(6) Empirical methods.
(a) Empirical methods may be used to
calculate T10, if the purveyor demonstrates to the department's satisfaction
that system components have configurations analogous to components on which
tracer studies have been conducted and results have been documented.
(b) The purveyor shall submit to the
department for review and approval engineering justification for determining
T10 using empirical methods. As-built drawings of system components in their
current configurations shall be submitted with the engineering
justification.
(c) A professional
engineer registered in the state of Washington shall prepare the engineering
justification for determining T10 using empirical methods.
Statutory Authority: RCW 43.02.050 [43.20.050].
99-07-021, § 246-290-636, filed 3/9/99, effective 4/9/99. Statutory
Authority:
RCW
43.20.050. 93-08-011 (Order 352B), §
246-290-636, filed 3/25/93, effective
4/25/93.
