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PUBLIC MONITORING SYSTEM FREQUENCY
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CONTAMINANT
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MINIMUM MONITORING FREQUENCY
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APPLICABLE SYSTEMS
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Bacteria
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Monthly or quarterly, depending on system size and type
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CNT
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Protozoa and
Viruses
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Continuous monitoring for turbidity, monthly for total and fecal coliforms, as
indicators
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CNT
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Volatile Organics
(e.g. benzene)
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Groundwater systems, annually for two consecutive years; surface water systems,
annually
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CN
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Synthetic Organics
(pesticides)
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Larger systems, twice in three years; smaller systems, once in three years
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CN
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Inorganic/Metals
and Nitrites
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Groundwater systems, once every three years; surface water systems, annually
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CN for most, CNT for nitrates
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Lead and Copper
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Annually
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CN
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Radionuclides
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Once every four years
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C
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C=Community;
N= Non-Transient, Non-Community;
T=Transient, Non-Community.
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Source: TCEQ, 2002 Draft Water Quality Inventory, September 2002,
5-3 - 5-5.
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Under the federal Safe Drinking Water Act, the level of regulation depends on the type of system. The law
classifies public water systems into two major categories. Those serving permanent populations like cities and towns are called "community systems." Those
serving facilities like hotels, restaurants, youth camps, highway rest stops, and travel-trailer campgrounds are called "noncommunity systems." These noncommunity
systems are further divided into those serving a transient population, such as restaurants and campgrounds, and those serving a nontransient
population, such as hotels and schools. In Texas there are about 4,600 community systems and 2,600 noncommunity systems.*
Transient noncommunity systems are required only to monitor and treat for nitrate, nitrites, turbidity,
disinfection and total and fecal coliform. Both community systems and nontransient noncommunity systems must monitor and treat water to standards set by the federal
government and enforced by the states, although presently nontransient noncommunity systems are not required to monitor for total trihalomethanes and
radioactive particles. Communities with less than 15 connections or 25 people are not considered to be "public water systems" and are therefore not regulated.
Beginning in 1993, public water systems were required to begin testing their treated water for the presence of
organic compounds. Between then and the end of 1995, samples for organic chemical analysis were taken for all 5,000 community and all nontransient noncommunity
(such as schools and prisons) public water supply systems in Texas. By the end of 1998, all 5,000 systems were tested again for organic compounds as part of the three-year cycle.*
Previously, all pesticide samples were analyzed by state field inspectors and taken at the entry point—where the treated
waters enter the distribution system. More recently, these samples are being collected by the Texas Rural Water
Association under a contract with the state. Under TCEQ regulations, if a pesticide is detected at any level, a confirmation
sample is taken. If confirmed, then public water systems are required to conduct quarterly samples (every three months)
until the water tests reliably and consistently below the maximum contamination level. While groundwater supply systems
must monitor only for a minimum of two quarters to determine whether there is a problem, surface water systems must conduct samples for a minimum of one year.*
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