Friday, September 30, 2011

DEQ to up allowable E. coli in river

Standards increase due to ‘calculation error’

Express Staff Writer

The Idaho Department of Environmental Quality is planning to increase the amount of allowable E. coli bacteria in the Big Wood River basin, but officials say there would be very little impact on water quality.

"What we're doing here is correcting an error we made," said Marti Bridges, a program manager for the department's water quality division. "In reality, it's a bookkeeping chore."

The new allowable amounts of E. coli are based on the official capacities of wastewater treatment plants in Hailey, Ketchum and The Meadows mobile-home park. Bridges said the original calculations were based not on capacity, but on current operations.

Because the plants were designed with room for growth, they were not operating to capacity. Bridges said that resulted in errors in the calculations of the mean allowable amount of E. coli in water being discharged from the plants.

She said the error came to light when the Hailey wastewater treatment plant applied for a permit renewal.

The mean proportion of allowable cfus, or "colony-forming units" of E. coli per 100 mililiters remains the same—126 cfus per 100 ml. But the total amount of allowable E. coli will increase, Bridges said.

Public comment on the changes can be submitted through Oct. 21 on the department's website,, or by mail to Marti Bridges, TMDL program manager, Idaho DEQ State Office, Water Quality Division, 1410 N. Hilton, Boise, ID 83706.

Bridges can also be reached at

Bridges emphasized that the increased allowable amount of E. coli would not pose a threat to local water quality.

"We're not in the business of creating water-quality problems," she said.

Katherine Wutz:

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