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<br />002069 <br /> <br />present, Tijuana's wastewater collection services approximately 70 percent ofTijuana's <br />residents (Guzman 1998). In addition, many existing sewer lines are aging and in poor <br />structural conditions. One result of the wastewater infrastructure deficit, along with aging <br />sewer lines, is that raw sewage frequently flows into the city's canyons and rivers. These <br />renegade sewage discharges degrade water quality in the city's rivers, groundwater <br />basins, and coastal waters. During the research period (June and early July 2000), raw <br />sewage flows were observed entering the Alamar River. <br /> <br />Besides raw sewage, nonpoint source pollution from agricultural and urban land uses <br />degrades water quality in the Alamar River. Nonpoint source pollution includes <br />human/animal waste, chemicals, oil, fertilizers, pesticides, trash, and other substances <br />that have collected on the ground, and are washed into the river by storm water runoff <br />(Michel 2000). In the case ofthe Alamar River, the most visible type of nonpoint source <br />pollution were large piles of illegally dumped trash originating from residential, <br />industrial, and commercial sources. Nonpoint source pollution contamination is most <br />severe during Tijuana's wet weather season. According to Gersberg and others, (2000), <br />storm water flows in Tijuana contain heavy metals that are considered toxic and include <br />lead, copper, cadmium, and zinc? In addition, storm water flows enter sewer lines <br />resulting in line breaks and overflows (Michel 2000). Contamination from raw sewage <br />and storm water flows poses a risk to potable water supplies in the aquifers. <br /> <br />The Tecate River is located in the northeast part of the state of Baja California. It <br />flows through the City of Tecate, into the United States via Cottonwood Creek, and the <br />surface water flows of these two water bodies eventually enter the Alamar River. The <br />Tecate River is a tributary that feeds into the Alamar River and Tijuana River system. At <br />present, effluent is discharged from Tecate's wastewater treatment plant and the treated <br />water is not in compliance with Mexico's wastewater treatment standards (Rodriguez <br />2000). Pollutants discharged into the Tecate River eventually flow downstream to the <br />Alamar River, the Tijuana River, and the Tijuana River Estuary. In previous years, water <br />quality tests conducted by UABC's Chemistry Department have detected significant <br />amounts of heavy metals and dissolved organics in the Tecate River. <br /> <br />During the BorderLink field research study, chl~mistry students from UABC Tijuana <br />conducted preliminary water quality analysis of surface and groundwater quality in the <br />Alamar River and upstream sites in the Tecate River. Visual observations ofthe surface <br />water in the Alamar River quality revealed the following: <br /> <br />. Drainage areas with storm water and/or wastewater flows that are not contained or <br />treated. These flows seem to originate from businesses and industrial plants in the <br />Mesa de Otay industrial sector. <br />. Illegal dumping of trash <br />. Leaking septic tanks and latrines that degrade surface and groundwater quality <br />. Foul odors in surface water flows <br /> <br />2 In residential areas, chromium, copper, and lead pollutant lc~vels were higher than in areas with industrial <br />land uses. This result is surprising since the assumption has been that export manufacturing plants or <br />maquiladoras are the primary source of pollutants in water bodies (Gersberg et. al. 2000). <br /> <br />13 <br />