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SEGMENTS WITH HIGH AND MODERATE POTENTIAL FOR TOXIC CHEMICAL
IMPACTS ALONG THE RIO GRANDE,
PHASE I OF RIO GRANDE TOXIC SUBSTANCES STUDY
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Source: Texas Natural Resource Conservation Commission, 1996
Regional Assessment of Water Quality in the Rio Grande Basin (1996), Appendix B.
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Because of concern over toxic contamination from industrial and agricultural sources in the
Rio Grande, which forms the border between Texas and Mexico, the U.S. and Mexican main federal environmental agencies, as well as the TCEQ (then known as the TNRCC), the
Texas Parks and Wildlife Department (TPWD), and the Texas Department of Health, conducted a series of toxic studies along the Rio Grande and its tributaries.
The first phase of the study, conducted in 1992 and 1993 and released to the public in
1994, found a disturbing trend of high levels of toxics in water, sediment, and fish in several of the mainstem monitoring sites and in almost all the tributaries. The study
monitored 19 mainstem sites and 26 tributary sites. At least one toxic substance was found in water, sediment, or fish tissue that exceeded at least one screening criterion at
each of the sites.*
The 30 chemicals that exceeded screening
levels included some of significant concern, such as PCBs, cyanide, mercury, lead, and residual chlorine. In 1995
Mexican and U.S. agencies conducted Phase II of the study, sampling 27 sites on the mainstem and 19 on tributaries in low-flow conditions.* The report confirms the Phase I findings: for significant reaches of the Rio Grande, such as
downstream of El Paso-Ciudad Juárez, Laredo-Nuevo Laredo, and Ojinaga-Presidio and in the Amistad Reservoir, there is a high potential for toxic contamination.* Field work for Phase III of the Rio Grande/Rio Bravo study was conducted in
1998 from El Paso to Big Bend National Park; nonetheless,the data has not been released.
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NUMBER OF BORDER RESIDENTS WITHOUT ADEQUATE WASTEWATER TREATMENT
FACILITIES BY COUNTY, 1996
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Source: Texas Water Development Board, Water and Wastewater Needs
of Texas Colonias: 1996 Update (1997).
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While the treatment and discharge of most wastewater in Texas is managed through the
permit system, some effluent is discharged into surface waters without treatment. In 1996, the TWDB estimated that 380,000 Texas residents lived in 1,500 unincorporated subdivisions
within 100 miles of the Texas-Mexico border that lacked either proper potable water or wastewater treatment service.* The majority
of "colonias," as they are known, were concentrated in Hidalgo, Cameron, and El Paso counties.
Most of these Texans used improperly operated septic tanks, cesspools, outhouses,
privies, or no treatment at all before discharging their wastewater directly into surface water or into the ground. This practice affected the quality of both groundwater and surface water.
The situation has improved. In recent years, state and federal funds have been spent to
bring many of these colonias into regional wastewater and water systems. As of May of 2003, 47 projects costing more
than $225 million helped over 125,000 colonia residents receive potable water and/or wastewater treatment. In
addition, another 70,000 colonia residents will benefit from projects costing about $200 million that are under
construction. Finally, according to the TWDB, if all the projects currently completed, under construction, in the design
or in the planning stages are actually completed, over 260,000 colonia residents would receive water or centralized wastewater treatment service.*
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UNTREATED OR PARTIALLY TREATED WASTEWATER DISCHARGED ALONG THE
TEXAS-MEXICO BORDER FROM MEXICAN CITIES, 1998*
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*Figures are in millions of gallons per day.
Note: Nuevo Laredo has operated a
secondary treatment wastewater plant since 1996. However, an estimated 4.3 of more than 21 million gallons a day is still going into the river without passing
through the treatment plant. In 1998, Ciudad Juárez began construction of a primary treatment plant, while Ciudad Acuña and Piedras Negras began construction of
secondary treatment plants in 2000.
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Source: U.S. Army Corps of Engineers, International Boundary and
Water Commission Sanitary Issues (Fort Worth: U.S. Army Corps of Engineers, September 1992). Additional Source: John M. Bernal, Office of the Commissioner,
International Boundary and Water Commission, United States Section, letter to Mary Kelly, Texas Center for Policy Studies, September 19,1997.
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The Rio Grande, the river that forms part of the border between Texas and Mexico, serves
as both the major source of drinking water and the principle recipient of wastewater for the region. Water quality for many segments of the Rio Grande has been severely degraded over
the years, in part because of the discharging of untreated or partially treated wastewater by Mexican cities, as well as because of a persistent drought in the 1990s which has
concentrated pollution in the river.
In the mid 1990s, the Mexican border cities of Juárez, Ojinaga, Acuña, Piedras Negras,
Reynosa, and Matamoros were discharging an estimated 151 million gallons of wastewater into the Rio Grande and Gulf of Mexico per day. About 88 million gallons per day was
untreated. The remaining 63 million gallons received only primary treatment, which means that solids and sludge have been removed but no chlorination or other chemical or biological
treatment of the wastewater has occurred.*
Since that time, both the U.S. and Mexican governments have put in considerable effort to
build wastewater treatment plants along the Texas-Mexico border. In fact all major border cities now either have a treatment plant operating or in construction. Thus, in 1996 the
U.S. and Mexican governments funded the construction of a joint wastewater treatment facility for Nuevo Laredo; however, the plant still does not cover all of the
city's residents, and some untreated wastewater still flows from the city. In 1997, the Border Environment Cooperation
Commission (BECC) certified a pair of "advanced" primary wastewater treatment plants for Ciudad Juárez, which were
constructed with $31.5 million in grant and loan dollars from the United States and Mexico packaged through the North
American Development Bank (NADBank), created along with the BECC in legislation parallel to the North American Free Trade Agreement.* The plants were fully operational by 2001. Later, loans and grants were approved for the
construction of wastewater treatment plants for Piedras Negras ($56.82 million total project cost), Ciudad Acuña
($78.8 million total project cost) and Reynosa ($83.4 million total project cost). In 2003, the NADBANK approved a grant to help Ojinaga update its wastewater treatment plant.*
Despite these advances, significant portions of the Rio Grande do not meet standards for aquatic life and contact
recreation uses, in large part because of the large amount of discharged untreated wastewater, runoff from both urban
and rural communities, all of it compounded by the limited flow and availability of water. For example, in 2002, the
TCEQ listed five of the 14 segments making up the Rio Grande as not meeting water quality standards for a variety of
pollutants, including elevated levels of bacteria, ambient toxicity in the water, chloride, and total dissolved solids.* In
2001, the Rio Grande actually dried up before it reached its outflow as drought and overuse of water conspired to create a huge sand bar where the Rio Grande once flowed.
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