Mario Castaneda, Water Border Technical Coordinator

Water Quality Division, Arizona Department of Environmental Quality

3033 N. Central Avenue, Phoenix, AZ 85012

Phone: (602) 207-4409

Water pollution is one of the principal environmental and public health problems facing the U.S./Mexico Border area. Deficiencies in the treatment of wastewater, the disposal of untreated effluent, and the inadequate operation and maintenance of treatment plants result in health risks to border communities. In some cases raw or insufficiently treated wastewater flows to surface and groundwater sources in urban and rural areas. In addition, potential contamination to groundwater from point sources exists in the area due to the increased industrial activity on both sides of the border. Groundwater is the major drinking water source for most border communities. Binational efforts are being undertaken under the U.S./Mexico Border 21 program to address these concerns. This binational program has also identified surface water and groundwater quality monitoring as an objective to characterize and determine the status of and changes in water resources in the border area. Also, it has identified the need to collect and analyze water quality data using standard sampling methodologies on both sides of the border. This paper describes the efforts that the Arizona Department of Environmental Quality has undertaken in participating on binational water quality projects in the Arizona-Sonora border. Two different approaches for binational cooperation on water quality monitoring will be presented. Water quality data collected and analyzed by both countries using commonly agreed sampling methodologies and data quality objectives will be presented and discussed.

The growth of population and industry in Mexico’s northern border region has put increased pressure on state and municipal governments in the border region to provide effective and efficient public services particularly in the area of potable water and wastewater. Water pollution is one of the principal environmental and public health problems facing the U.S./Mexico border area. A border trade agreement and changing economic conditions in Mexico increased industrial activity in the border region, more notably in the Sonoran side. Labor and assembly costs are much lower in Mexico, and environmental regulations in the past have not been as strict. Today, there are more than 2,200 maquiladoras (American assembly plants) along the U.S.-Mexico border and about 80 just in Nogales, Mexico, where the population has grown to nearly 400,000 people. Population growth in Nogales, Sonora is estimated at 4 percent per year. Industry growth there overshadows Nogales, Arizona, with a population of less than 20,000.

Groundwater is the major drinking water source for most of the border communities in the Arizona-Sonora border region. The lack of basic inventory and monitoring information pertaining to water resources prevent a comprehensive understanding of watershed and regional natural resources issues. Lack of quantitative information concerning the natural recharge and the possible limitations of many of the groundwater supplies lead to uncertainties as to the future of these water resources. Binational efforts are being undertaken under the U.S./Mexico Border 21 Program to address these concerns. The U.S./Mexico Border 21 Program is a binational effort to work cooperatively toward sustainable development through protection of human health and the environment as well as proper management of natural resources in each country.

The 1996 Border 21 Framework Document defined five-year objectives for the border environment and described the mechanisms for fulfilling those objectives (EPA, 1996). One of the key objectives was identifying surface water and groundwater quality monitoring to characterize and determine the status of and changes in water resources in the border area. Another objective was the development of environmental indicators to use in evaluating the effectiveness of border environmental policy. However, the monitoring activity and the use of environmental indicators for the border area require sharing environmental data by the U.S. and Mexico from the binational watersheds.

The Arizona Department of Environmental Quality (ADEQ) has been actively participating on the EPA Border 21 activities (Castaneda, 1995). Several binational surface water and groundwater monitoring projects have been already implemented along the Arizona-Sonora border. ADEQ has recognized the importance of developing a consistent environmental policy in dealing with water quality issues along the border and in participating on binational water quality projects since both surface water and groundwater flow to both sides in these binational watersheds. However, this participation has been complex and difficult because of the different legal environmental jurisdiction in both countries. Binational water quality (and quantity) issues between both countries are dealt by the International Boundary and Water Commissions (IBWC). Direct contact between the border states (i.e., Arizona and Sonora) to exchange environmental information is difficult. In addition, surface water and groundwater quality (and quantity) issues in Mexico are the sole responsibility of the Mexican federal government. The Mexican states have had little or no jurisdiction on these matters. On the other hand, both the federal and state governments in the U.S. deal with water quality issues but water quantity is handled by the states alone.

It has been recognized in the U.S. that data comparability needs to be improved so that organizations can use information from multiple sources (ITFM, 1995). Differences in methods used to collect and analyze water quality samples frequently pose impediments to making full use of the data from other sources. And even if the methods are compatible, adequate quality-assurance programs are needed to quantify the precision, accuracy, and integrity of environmental data to ensure that these data can be used for the appropriate application. The importance of these differences is compounded when environmental data are exchanged between two nations.

In an effort to standardize water quality sampling methodologies along the Arizona-Sonora border region, the Water Resources Research Center (WRRC) of the University of Arizona under contract with ADEQ started developing a bilingual field manual for water quality sampling in 1993. Several U.S. and Mexican institutions participated in the manual review process. The manual was finalized and printed in March 1995. A second printing was made in July 1996 (WRRC, 1996). The need of implementing this manual as an official guidance document by the States of Sonora and Arizona in all groundwater/surface water quality sampling being performed in both border states was obvious.

This paper describes the efforts that ADEQ has undertaken in participating on binational water quality monitoring projects in the Arizona-Sonora border. Two different approaches for binational cooperation on water quality monitoring will be described: the formal approach that was coordinated by the U.S. and Mexican federal governments through the IBWC umbrella and a more direct interaction of ADEQ with the State of Sonora, Sonora local municipalities, a Sonoran non-governmental-organization (NGO), and the University of Sonora.

The formal ADEQ binational interaction can be exemplified by its participation on the Binational Nogales Wash Groundwater Monitoring project. This is the first groundwater quality monitoring project that has been implemented along the U.S.-Mexico border. Nogales Wash originates 7 miles south of the U.S./Mexico International Boundary and flows north through Nogales, Sonora, Mexico and Nogales, Arizona, U.S.A. Perennial flow in Nogales Wash is fed by springs near its head. However, grey water and sewage has contributed to the flow. ADEQ has monitored surface water flows in the Nogales Wash in the U.S. side and had documented high fecal coliform bacteria levels, ammonia, and heavy metals in the past (Earth Technology, 1990, 1993). A disinfection system installed on the Mexican side of the border has helped reduce the risk from raw sewage.

The wash joins the Santa Cruz river just upstream of the Nogales International Wastewater Treatment plant discharge. This plant, located in Nogales, Arizona and owned and operated by the IBWC, treats waste water from both Nogales, Sonora and Nogales, Arizona, AZ. Although the plant has been expanded in one occasion, it has already exceeded its design capacity again and binational efforts are being made to address this situation. An existing international wastewater trunk line runs along the wash. The condition of this trunk line has deteriorated and infiltration/exfiltration problems have been reported by both cities. A facility planning project is underway to fix these problems and to search for the best alternative to satisfy the wastewater treatment needs of the region.

The regional groundwater flow is generally to the U.S. in this area. Previous binational water quality monitoring activities that took place in the Nogales Wash area in 1990 showed concentrations of nitrates and volatile organic compounds (VOCs) exceeding the Mexican water quality standards in the Nogales Wash aquifer in Nogales, Sonora (The Udall Center, 1993). However, sampling methods and quality assurance problems were cited by the IBWC and the water quality data were not considered valid by both countries. As a result, official binational meetings were initiated in 1992 to address the growing concerns about the groundwater quality in this area. Based on a binational agreement between the U.S. and Mexico, the IBWC developed a joint report to allow for a joint U.S./Mexico groundwater quality study in the Nogales Wash. Federal, state, county, and city representatives from both sides of the border participated on this study. The project, funded by the Environmental Protection Agency (EPA) and its Mexican counterpart was implemented to collect reliable soil and groundwater quality data from the vadose zone and the alluvial aquifer along the wash. Data collection would document whether or not surface activities and discharges to the Nogales Wash have significantly affected groundwater quality. Thirteen ground water monitoring points within approximately 5 miles north and south of the International Boundary were sampled. Groundwater monitoring wells were constructed for this purpose. Representatives of the participating agencies from the United States and Mexico selected and agreed upon sites for monitoring well placement. All sites were located along the Nogales Wash or its tributaries in areas where the shallow alluvial aquifer is present. Most of the sites lied down gradient of or adjacent to areas where past or present land use included industrial activity or development that may have had an impact on groundwater quality. In this manner, the location of potential sources of groundwater contamination could be narrowed to a smaller region within the urban area for a more focused study by the appropriate authorities.

A well construction plan, developed in May 1993 by ADEQ and IBWC, was approved by the EPA in January 1994. This work plan was negotiated with Mexico and agreed upon in October 1996. Drilling of the monitoring wells in the U.S. side was completed in February 1996 and in Mexico in February 1997. Although different drilling techniques were used by both countries, all monitoring wells were completed similarly. A work plan presenting the proposed sampling procedures and quality assurance methods for this study was initially developed by ADEQ specifically for this project in 1993. A revised version containing the proposed U.S. sampling and analysis methodology was approved by EPA in September of 1995. Sampling of these monitoring wells was performed quarterly for one year and ended in February 1998. Although agreement was reached on the sampling methodologies to be used by the group prior to sampling, no prior agreement was reached on the lab methodology and respective method detection limits to be used for this study and each country analyzed the samples according to the best laboratory methodology available to them. Negotiations to approve both documents took considerable amount of efforts and time. A training session on the project sampling procedures was provided to all project participants prior to the sampling activities. A binational project interim report containing sampling data from the first two quarterly sampling activities was finalized in June 1998. A final report is being developed by the participating agencies and is expected to be completed by December of 1998.

Split samples were collected by both groups and tested for Volatile Organic Compounds (VOCs), Total Petroleum Hydrocarbon (TPH), major cations and anions (MCAS), trace metals (26 constituents), total and fecal coliforms, and field parameters. The laboratories responsible for the analyses conducted in this project were certified by the respective country’s laboratory certification process. Table 1 presents a list of some of the parameters analyzed and their respective practical quantitation limits reported from both labs.

Project quality control checks were performed using duplicate samples, field blanks, and trip blanks collected by each group. Precision was determined through duplicate analyses and calculated as a relative percent difference. Precision for field duplicate sample analysis were set to 30% or lower for VOCs and to 35% or lower for metals. Accuracy was determined by the analyses of surrogate and matrix spiked samples and calculated as percent recovery. Recovery was generally expected to be within 70-130%. The limits for precision and accuracy were applied to any measurement that was at least ten times greater than the background (noise) level of the detector or the detection limit of the method. Cation/anion balances were calculated for each sample sent to the U.S. lab. The balance was not more than 10% discrepant. No information on cation/anion balances has been provided by Mexico yet. Although performance standards samples were proposed for this study, Mexico did not agree to incorporate them during the sampling activity.

Figures 1, 2, and 3 present a comparison of the U.S. and Mexican data for some of the constituents detected during the April 1997 sampling event. Mexico detected and reported higher values for silica, alkalinity, and pH than the U.S. The U.S. detected and reported higher values of nitrates, arsenic, and tetrachloroethylene (PCE) than the Mexican group. The reasons for these data differences are being investigated by the binational group and will be included in the final project report.

Figure 4 presents a mean of the respective relative percent difference (RPD) for the constituents analyzed by both labs (considered as duplicate samples). It also presents the mean of the individual RPDs calculated from the duplicate samples collected by each group (two duplicates by each group for April 1997). Both sampling teams met the individual precision criteria established for this project. The use of performance standard samples could have been an useful reference for the discrepant data.

Preliminary data from this project has shown the presence of groundwater contaminated with PCE exceeding both U.S. and Mexican aquifer water quality standards in the Sonoran Nogales Wash aquifer. This finding has been supported by lab data from both countries. Additional steps are being discussed with Mexico to locate and assess potential PCE sources in the area.

A less formal but more direct approach to ADEQ binational activities can be exemplified by the water quality monitoring activities being performed in the eastern part of the Arizona-Sonora border, in the Douglas-Agua Prieta and Ambos Nacos area. These communities are presented with a variety of water quality issues. Groundwater flows generally to Mexico. There is a groundwater sulfate plume produced by leachate from mine tailings located in Arizona with concentrations exceeding the secondary drinking water standards. Also, There is a wastewater treatment plant located in Douglas Arizona which treated effluent is being discharged into Mexico without chlorination (at Mexico’s request). In addition, there is a wastewater treatment lagoon located in Naco, Sonora very close to the international boundary that has overflowed into Arizona in the past.

With assistance and guidance from non-governmental organizations and the University of Sonora, the Sonoran border municipalities of Cananea, Naco, and Agua Prieta implemented a water quality monitoring project to assess the water quality of the three municipal areas, the San Pedro River (which flows to the U.S.), and the Sonora River (not a binational river) to allow for a more thorough depiction of water quality in the northern Sonora, Mexico. This effort, named the "Sonoran Regional Water Quality Sampling Project," was to provide a baseline of environmental information regarding surface water and groundwater quality in the transboundary watersheds of the region. The University of Sonora’s Department of Scientific Research and Technology ( DICTUS), was subcontracted by the Sonoran municipalities to carry out the water quality monitoring and assessment for this project. The U.S. Agency for International Development (USAID) supported this project through a $100,000 grant administered by the International City/County Management Association (ICMA).

The Sonoran municipalities requested ADEQ support in carrying out this project. ADEQ was prepared to fulfill a supporting role for this Mexican project to enhance binational communication, transboundary relationships, technology transfer, and to develop an enhanced understanding of the environmental conditions in watersheds shared by Arizona and Sonora. ADEQ’s role and participation in this Mexican project was premised upon the prior awareness and approval of appropriate Mexican agencies as demonstrated by the U.S. and Mexico Sections of the IBWC. The enhancement of institutional capacity in Mexico was a primary objective of this project. By collaborating in this effort with ADEQ and the Arizona State Laboratory of the Arizona Department of Health Services (ADHS), expertise would be shared with the University of Sonora and the municipalities of Cananea, Naco, and Agua Prieta to facilitate pursuit of environmental assessment and management efforts focused on water quality.

The ADEQ provided laboratory in-kind services for this project for analytical capabilities which had yet to be developed at the University of Sonora. Specifically this included analysis of volatile organic compounds (VOCs) and pesticides in samples of water and sediment. The State of Arizona provided up to $20,000 for such analysis of samples collected in Mexico and is helping DICTUS arrange a technology transfer opportunity in Phoenix between personnel from the University of Sonora and the ADHS State Laboratory. The purpose of this technology transfer opportunity is to provide guidance in the event that the University of Sonora in Hermosillo decides to pursue such analytical capabilities.

Phase I of this project was implemented in 1997. Surface water, groundwater, and sediments were sampled for VOCs, major cations and anions, and pesticides. Inorganics analysis were performed by DICTUS. VOCs and pesticides analysis were performed by the ADHS State lab. A sampling plan was developed by DICTUS with ADEQ support. The binational group used the ADEQ bilingual water quality sampling manual as a basis for this sampling plan. Precision and accuracy objectives were set similarly as those for the Nogales Wash groundwater project. An ADEQ-DICTUS specific Memorandum of Understanding (MOU) that clarified the respective institutions roles and data confidentiality was developed for this binational interaction. Because of the specific requirements of the ADEQ-DICTUS MOU, no split samples were sent to Arizona for analysis. The final project report, which had been scheduled for completion in April 1998, has been delayed and unfortunately, no data is available yet to present in this technical paper.

Phase II of this project will expand the monitoring activities on the areas of concern that might be detected during the Phase I. The ADEQ-DICTUS MOU has been amended to include inorganic lab analysis support from the ADHS State lab for this project.

These projects have provided an opportunity for ADEQ to collaborate in the understanding of the water quality conditions at these binational watersheds. It also has provided the opportunity to exchange and compare sampling methodologies with different Mexican federal and state regulatory agencies. There were no major differences on the water quality sampling methodologies used by both groups. However, major differences in laboratory analytical techniques need to be discussed and understood. There is a need to use performance standard samples in these binational monitoring projects. This understanding will be helpful when exchanging water quality data between both countries during the development of the border water quality environmental indicators taking place within the U.S.-Mexico Border 21 process.