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VIOLATIONS OF ORGANIC AND INORGANIC MCLS BY CONTAMINANT, FY 2002
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|
CONTAMINANT
|
NUMBER OF VIOLATIONS
|
|
Nitrate Nitrogen
|
59
|
|
Flouride
|
53
|
|
Combined Radium
|
18
|
|
Gross Alpha
|
15
|
|
Arsenic
|
3
|
|
Selenium
|
7
|
|
Asbestos
|
2
|
|
Barium
|
1
|
|
Trihalomethanes
|
3
|
|
Total
|
160
|
|
Source: Texas Natural Resource Conservation Commission, Water
Utilities Division, 1998.
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In FY 2002, there were 160 violations of one of the primary organic and inorganic maximum containment levels.* Nearly all of the violations were related to inorganics such as nitrates, arsenic, fluoride, and selenium. In
addition to these violations, several hundred systems have violated the total coliform rule. For example, in 2000, the state reported that 129 systems violated the Total Coliform Rule.* In all, 240 different public water systems serving 998,095 people in Texas violated a health-based standard in Fiscal Year 2002 *
Beginning in 1993, public water systems were required to begin testing
their treated water for the presence of organic compounds. Between 1993 and 1997, nine water systems serving half a million people had at
least one sample exceeding the maximum containment level for atrazine, a herbicide.* However, in order for a system to be considered in
violation of the level requirements, the average of the four quarterly samples must be over the level. By 1998, only one system—the Aquilla
Water Supply District—was in violation of the standard, and only one water body is in violation of Texas Surface Water Quality Standards because of high atrazine levels.
Two drinking water contaminants pose the most acute threat to human
health: nitrates and bacteria. Nitrates in concentrations above the
national standard threaten the health of infants. Nitrates can react with the blood's hemoglobin, interfering with its ability
to carry oxygen and resulting in the sometimes fatal "blue baby" syndrome. Bacteria in contaminated water can cause diseases such as typhoid, cholera, infectious hepatitis, and dysentery.* These disease-causing bacteria are signaled by
high levels of coliform bacteria, itself a relatively benign bacteria. Fecal coliform bacteria are commonly found in human
and animal waste and may indicate sewage contamination and the presence of disease-causing organisms.
Lead in drinking water is another major concern. Lead usually enters the drinking supply from old lead pipes in homes,
from brass fixtures, or from lead-based solder in copper pipes.* Lead is now banned in the installation or repair of public
water systems and household plumbing. There were 68 exceedences of lead standards in 36 public water systems throughout the state in 1996 and 1997.* These systems must conduct anticorrosion and other tests to determine what is
affecting their systems and correct the problem. Fortunately, these systems represented less than three percent of all systems tested in the state.*
Finally, a newly emerging concern is what happens with the disinfectant (like chlorine) once it leaves the water treatment
plant. While chlorine helps eliminate any remaining pathogens, it also leads to the formation of dangerous particles called
trihalomethanes, or THM. THMs were regulated beginning in 1980 for systems serving populations over 10,000, and
today most systems have switched from free chlorine to other disinfectants, thus reducing the formation of THMs. Only a
few drinking water systems in Texas—located primarily in the Lower Rio Grande Valley—have exceeded THM standards in recent years.* However, in 2001 and 2002, the EPA finished expanding regulations for these and other disinfectant
by-products, and Texas has begun implementing these new regulations, which will likely bring some additional systems in Texas out of compliance.*
More recently, concern has been raised about perchlorate, a compound used in making weapons and rockets. In 2002,
the TCEQ reported that 11 Western Texas counties has elevated levels of perchlorate in their water supplies, and
concern about the possibility that this could be in the drinking water has been raised.* Curiously, in many of these water
supplies, there is no nearby weapon or rocket manufacturing activities. There is currently no MCL for perchlorate,
although TCEQ has developed some internal guidance on the topic and the EPA is developing an emergency MCL due to this newly identified threat.
|
PUBLIC WATER SYSTEMS WHERE PESTICIDES HAVE EXCEEDED THE MAXIMUM
CONTAMINANT LEVEL FOR ONE OR MORE SAMPLES, 1995-1997
|
|
SYSTEM
|
CONTAMINANT
|
YEAR OF EXCEEDENCE
|
|
City of Midlothian
|
Atrazine
|
1997
|
|
Sagemeadow Municipal Utility
|
Atrazine
|
1997
|
|
Aquilla Water Supply District (Gets water from City of Houston)
|
Atrazine, Alachlor
|
1997
|
|
City of Dawson
|
Atrazine
|
1997
|
|
Friona Municipal Water System
|
Atrazine
|
1997
|
|
City of Ft. Worth
|
Atrazine
|
1997
|
|
Combined Water Supply Corporation (Lake Tawakoni)
|
Atrazine
|
1997
|
|
City of Robinson
|
Atrazine
|
1996
|
|
City of Marlin
|
Atrazine
|
1995
|
|
Source: Texas Natural Resource Conservation Commission, Water Utilities Division, Organic Substances Database, 1997.
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