This animation illustrates how a standard Polychem chain and flight scraper system is assembled and installed.
Water Still not Safe to Swim in or Drink, Though
A report released by the International Boundary and Water Commission shows that the El Paso and Juárez, Chihuahua, sections of the Rio Grande river do not contain enough contamination to pose significant health threats, the Austin American-Standard reported.
The river was found to contain traces of heavy metals, including some that cause cancer, but the amounts are not large enough to threaten human health.
However, experts warn that this does not mean it is safe to swim in the water or drink unpurified water from the river, the Austin American-Standard reported.
Before making such recommendations, the commission would like more time to study the water and would require more information about Mexican rivers that flow into the Rio Grande.
The study was conducted by Mexican and U.S. officials. The report found that levels of arsenic, lead, cadmium, copper and nickel exceeded Texas screening levels. Concentrations of salts (chloride and sulfur) turned up farther downstream but are not unusual.
"Most of the heavy metals are naturally occurring or were from urban runoff, but they were not in amounts that are of concern," Daniel Borunda, environmental protection specialist for the commission's U.S. section, told the Austin American-Standard. "We also looked at urban discharges and pesticides and did not find any significant problems with those either."
Signs banning swimming and fishing remain posted in the West Mesa drain in the Upper Valley.
"It's a prevention measure more than anything else," said Irene Rivas, spokeswoman for the health district.