Researchers from San Diego State University are launching the second phase of a survey as they study the effects of pollution on Tijuana River Valley residents. For decades, the Valley has been plagued by untreated sewage flows that originate in Mexico. The Tijuana River not only carries the effluent, but also large quantities of chemicals and other pollutants into the U.S. side of the border and the Tijuana River Valley. In recent years, the contamination has gotten worse as Tijuana’s sewage infrastructure has collapsed and is constantly sending millions of gallons of raw sewage north of the border. On a daily basis, the stench can be overwhelming.