Noticeably absent from these efforts is participation from private businesses, many of whom have taken advantage of the cheap labor and lax environmental law enforcement in Mexico, contributing heavily to the pollution problems of this and other rivers along the US border.

The area in question of the Tijuana river snakes across the borders of San Diego, California and Tijuana, Mexico. Flooding has been a constant problem, causing loss of life and serious property damage and depositing sediment that threatens the Tijuana estuary. Pollution, however, is the major problem as the area has become more developed. Since the 1960s, migration has increased the population significantly, and inadequate sanitation facilities helped to make the area's beaches and estuary unpleasant and even dangerous places, where visitors risk contracting diseases such as salmonella, cholera and malaria.

The reason for this increase in population can be linked largely to an increase in industry. Maquiladoras, which are foreign-owned industry plants, have exploded in number over the past twenty years. In 1983, the number of maquiladoras numbered 140. In 1999, more than 3500 plants employed 1.2 million workers. The main fallout from the maquiladoras and the communities created around them are Aguas Negras. These black waters, which are toxic composites of residential and industrial waste, were discharged directly onto beaches in Tijuana, eventually ending up in the Tijuana watershed and California beaches as well. Maquiladoras are not only responsible for pollution, but for excessive water use. In 1995, the Samsung electronics plant in Tijuana was responsible for 5% of the area's water consumption.

Several efforts have been started since the 1980s to control the pollution problems, but these have been made largely by public concerns. The Tijuana River Watershed project is an effort sponsored by the National Oceanic and Atmospheric Administration and operated by San Diego State University in the US and El Colegio de la Frontera Norte in Mexico. The primary function of the watershed project is to facilitate a dialogue among watershed stakeholders and increase awareness of the area's problems. The International Boundary and Water commission has built two water treatment plants, one in Tijuana, the other in California as part of the "Clean Water Partnership" formed in 1990 between the US and Mexico.

NAFTA involvement is helping to improve the problems from the private sector end, if slowly. With maquiladoras losing their duty free status as of this year, it will become less advantageous for companies to establish so many waste-producing plants along the border. Also, pressure from NAFTA and the North American Development Bank has prompted companies to start including water treatment and recycling facilities in their plants.

Clean-up costs for the entire US-Mexico border are estimated to be as much as twenty billion dollars. Over four hundred million dollars alone has been spent on cleaning up the Tijuana river. It would be unfair to say that private industry has not played a role in financing some of these activities, but involvement has come too often from outside pressure or actual law and has been too low a priority.