Wednesday — February 18, 2004

Bellevue sewer plant nitrogen levels spike

DEQ and engineers push for solution

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"Bellevue in the last several years has had a hard time. The concern is that high nitrogen levels would eventually contaminate groundwater."

— GREG MISBACH, Idaho DEQ technical engineer

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By MATT FURBER
Express Staff Writer

Sewage treatment is still taxing municipal systems in the city of Bellevue. City superintendent Brian Whipple reported Thursday, Feb. 12, that tests of the city’s rapid infiltration basins show the system is currently spiking at 50 ppm for nitrogen, which is above acceptable levels for what comes out of a septic system.

Municipal thresholds are lower, Whipple said. "(The spike) will cause us to violate the minimum of 20 parts per million."

Idaho DEQ technical engineer Greg Misbach, who monitors the city’s plant, said the Twin Falls office regularly sees nitrogen spikes from various cities. He also said the standard for drinking water is less than 10 parts per million.

Misbach’s associate, assistant engineer Brian Reed, said spikes are usually an indication that there are operational or systematic treatment problems.

"We do monthly, quarterly and annual inspections on behalf of the EPA to see that municipal sewer systems are in compliance with NPDES permits," he said.

National Pollutant Discharge Emission Standards are the allowable limits of contaminants like nitrogen and organic material from a treatment facility that can be discharged to the river.

The city of Bellevue does not use a NPDES permit because it does not transmit treated wastewater to the Big Wood River. Instead, the city has a state permit for land application from a lagoon treatment system, which is a holding tank where sewage is treated before it is applied to fields.

"Bellevue in the last several years has had a hard time," Misbach said. "The concern is that high nitrogen levels would eventually contaminate groundwater."

But, the DEQ office is working with the city to find a solution to the problem, Whipple said.

The state has awarded the city a $120,000 matching grant to do a facility study that will help the city better understand the dynamics of the impacts and design an appropriate upgrade to the system.

"We have quite a few grants going (to various cities)," Misbach said. Bellevue is focused on the problem, he said.

The city has chosen to negotiate a contract with the Boise-based engineering firm, Keller and Associates for the study.

Mayor John Barton said once the contract is negotiated the final cost of the study will be determined.

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