September 16, 2009

High chloride levels found in 19 states

A U.S. Geological Survey study has found levels of chloride are elevated in groundwater and in many urban streams across northern U.S. states.

Researchers said levels of chloride -- a component of salt -- above the recommended federal criteria set to protect aquatic life were found in more than 40 percent of urban streams tested.

USGS scientists said elevated chloride can inhibit plant growth, impair reproduction and reduce the diversity of organisms in streams.

The effect of chloride on drinking-water wells was lower. Scientists said they found chloride levels greater than federal standards set for human consumption in fewer than 2 percent of drinking-water wells sampled in the study.

The researchers said the use of salt for deicing roads and parking lots during the winter is a major source of chloride. Other sources include wastewater treatment, septic systems and farming operations.

These findings are not surprising, but rather remind us of the unintended consequences that salt use for deicing may have on our waters, said Matthew Larsen. USGS associate director for water. Transportation officials continue to implement innovative alternatives that reduce salt use without compromising safety.

The study examines chloride concentrations in parts of 19 northern states, including 1,329 wells and 100 streams.

The report by John Mullaney, David Lorenz, and Alan Arntson is available at