| specific assessment elements with respect to the size and type
of the public water system and the size, type, and characteristics
of the distribution system.
(27) Level 2 assessment--An evaluation to identify
the possible presence of sanitary defects, defects in distribution
system coliform monitoring practices, and (when possible) the likely
reason that the public water system triggered the assessment. A Level
2 assessment provides a more detailed examination of the public water
system (including, but not limited to the public water system's monitoring
and operational practices) than does a Level 1 assessment through
the use of a more comprehensive investigation and review of available
information, additional internal and external resources, and other
relevant practices. Minimum elements include review and identification
of atypical events that could affect distributed water quality or
indicate that distributed water quality was impaired; changes in distribution
system maintenance and operation that could affect distributed water
quality (including, but not limited to water storage); source and
treatment considerations that bear on distributed water quality, where
appropriate; existing water quality monitoring data; and inadequacies
in sample sites, sampling protocol, and sample processing. The public
water system must conduct the assessment consistent with any executive
director directives that tailor specific assessment elements with
respect to the size and type of the public water system and the size,
type, and characteristics of the distribution system. The public water
system must comply with any expedited actions or additional actions
required by the executive director in the case of an Escherichia coli (E.coli) maximum contaminant
level violation.
(28) Locational running annual average (LRAA)--The
average of analytical results for samples taken at a specific monitoring
location during the previous four calendar quarters.
(29) Maximum contaminant level (MCL)--The maximum concentration
of a regulated contaminant that is allowed in drinking water before
the public water system is cited for a violation. MCLs for regulated
contaminants are defined in the applicable sections of this subchapter.
(30) Maximum residual disinfectant level (MRDL)--The
disinfectant concentration that may not be exceeded in the distribution
system. There is convincing evidence that addition of a disinfectant
is necessary for control of waterborne microbial contaminants.
(31) Minimum acceptable disinfectant residual--The
lowest disinfectant concentration allowed in the distribution system
for microbial control.
(32) Operational evaluation level (OEL)--Calculated
level of total trihalomethanes (TTHM) or haloacetic acid group of
five (HAA5), an exceedance of which requires a system to perform an
evaluation of factors in the distribution system contributing to disinfection
by-product formation and submit an operation evaluation report as
described in §290.115(e)(2) of this title (relating to Stage
2 Disinfection Byproducts (TTHM and HAA5)). The OEL at any monitoring
location is the sum of the two previous quarters' results plus twice
the current quarter's result, divided by 4 to determine an average.
(33) Raw water--Water prior to any treatment including
disinfection that is intended to be used, after treatment, as drinking
water.
(A) Raw groundwater is water from a groundwater source.
(B) Raw surface water is any water from a surface water
source or from a groundwater under the direct influence of surface
water source.
(34) Raw groundwater source monitoring--Fecal indicator
sampling at untreated groundwater sources including triggered source
water and assessment source monitoring.
(35) Sanitary defect--A defect that could provide a
pathway of entry for microbial contamination into the distribution
system or that is indicative of a failure or imminent failure in a
barrier that is already in place.
(36) Seasonal public water system--A noncommunity public
water system that is not operated as a public water system on a year-round
basis and starts up and shuts down at the beginning and end of each
operating season.
(37) Significant deficiency--Significant deficiencies
cause, or have the potential to cause, the introduction of contamination
into water delivered to customers. This could include defects in design,
operation, or maintenance of the source, treatment, storage, or distribution
systems.
(38) Specific ultraviolet absorption at 254 nanometers
(nm) (SUVA)--An indirect indicator of whether the organic carbon in
water is humic or non-humic. It is calculated by dividing a sample's
ultraviolet absorption at a wavelength of 254 nm (UV254) (in inverse
meters) by its concentration of dissolved organic carbon (DOC) (in
milligrams per liter).
(39) Total organic carbon (TOC)--The concentration
of total organic carbon, in milligrams per liter, measured using heat,
oxygen, ultraviolet irradiation, chemical oxidants, or combinations
of these oxidants that convert organic carbon to carbon dioxide, rounded
to two significant figures. TOC is a surrogate measure for precursors
to formation of disinfection by-products.
(40) Total trihalomethanes (TTHM)--The sum of the chloroform,
dibromochloromethane, bromodichloromethane, and bromoform concentrations
in milligrams per liter, rounded to two significant figures after
summing.
(41) Triggered source water monitoring--Raw groundwater
source monitoring required for systems not providing at least 4-log
treatment of viruses when a routine distribution coliform sample is
positive.
(42) Trihalomethane (THM)--One of the family of organic
compounds named as derivatives of methane, wherein three of the four
hydrogen atoms in methane are each substituted by a halogen atom in
the molecular structure.
(43) Wholesale system--A public water system that delivers
water to another public water system.
(44) 4-log treatment--At least 99.99% (4-log) treatment
of viruses using inactivation, removal, or an executive director-approved
combination of 4-log virus inactivation and removal. The 4-log treatment
must be able to be properly validated and achieved before the first
connection of the specified water source.
|
| Source Note: The provisions of this §290.103 adopted to be effective September 13, 2000, 25 TexReg 8880; amended to be effective May 16, 2002, 27 TexReg 4127; amended to be effective January 9, 2008, 33 TexReg 198; amended to be effective November 8, 2012, 37 TexReg 8849; amended to be effective March 30, 2017, 42 TexReg 1466 |
