Agricultural waterways tested for E. coli in East San Joaquin Valley

Tests have revealed high levels of E. coli and a common pesticide in Merced and Madera county waterways, forcing nearly 1,000 farmers to grapple with potentially expensive cleanup efforts.

Officials say it's not known if the E. coli is the virulent strain that contaminated produce from the Salinas Valley in recent weeks. They also note that the bacteria have always been present to some degree in waterways.

William L. Rukeyser, spokesman for the water board, said E. coli is not necessarily something to worry about. It is "present in nature anywhere there are warm-blooded animals ... what is alarming is when you have contamination from a virulent strain."

The coalition began contacting individual landowners and pest control operators in the watersheds in August. Surveys are under way to determine how farmers are applying pesticides.

Members of the coalition — set up by the state to let farmers share costs of monitoring and problem-solving — will meet in Merced and Chowchilla this week and next to seek solutions.


The state water board began regulating discharges from irrigated farmland four years ago. The new regulations meant an end to what had been a 20-year exemption for growers from strict guidelines regulating pollutant runoff.

Klassen said the coalition's budget is about $800,000 a year. Members of the coalition pay, on average, about $1.50 per acre per year to monitor water.

If the coalition does not fix the contamination, farmers could be forced to get permits individually from the state. Permits could cost farmers tens of thousands of dollars a year, depending on the size of their operation, plus similar sums for water sampling.

Since July 2004, Duck Slough had 11 samples that showed an excessive E. coli bacteria count, Highline Canal had three excessive E. coli counts, Ash Slough two and the Merced River one, Klassen said. Ash Slough is in Madera County; the other waterways are in Merced County.

Three samples of water from Duck Slough contained chlorpyrifos, a chemical used in products that include Lorsban or Lock-On, in concentrations above water-quality standards. Klassen said the pesticide is used on alfalfa, field corn and almonds.

Tests revealed that Highline Canal has reached toxic levels seven times since July 2004, along with higher-than-acceptable chlorpyrifos levels on two occasions. The Merced River showed toxicity four times in that period.