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Five years after building a treatment plant at each of the city’s three wells, Woodburn officials are working on a new system to disinfect the water. The city released a request for proposals on Jan. 11.

Cities such as Woodburn that use groundwater typically don’t have the same contamination worries as those using surface water, said Dan Brown, the city’s public works director. That makes his job convincing the public that such a treatment system is necessary a little harder.

Residents ask why they need to put more money into water treatment just a few years after a $17 million upgrade. “They say, ‘We spent all this money on purifying groundwater;’ they’re saying ‘We don’t understand, Mr. Public Works Director, why we have to be disinfecting.'”

It’s true that Woodburn gets clean water from its wells, Brown said. The treatment system then removes iron and manganese from the water.

“The problem is you have very pure water as you pull it out of the wells and treat it,” Brown said, “but there’s no residual disinfection capability.” That means that any contaminant that gets into the water after it leaves the treatment plant could stay there.

Woodburn has 110 miles of water mains, some of which are more than 100 years old, Brown said. In 2007, midge flies got into this distribution pipeline.

City officials cleaned the system and sealed off entry points, but another infestation surfaced two years later. While midge flies don’t sicken people, Brown said, they’re never a welcome sight.

“When people see an organism in their drinking water, they freak out,” he said.

“As for a pathogen, they may not see it, but pathogens are a real concern.”

Woodburn’s system would use chloramine, a compound used as an alternative to traditional chlorine in disinfection. Chloramine stays in the water and even helps eliminate the film that builds up on the insides of pipes and storage tanks, Brown said.

San Francisco also uses a chloramine system, and Brown used that city as a model in Woodburn’s plans. In Oregon, Portland and Coos Bay also use chloramine.

San Francisco started using chloramine in 2004, after having used chlorine disinfection.

Treatment guidelines required the city to use a disinfectant that stayed in the water, said Andrew Degraca, water quality division director for the San Francisco Public Utilities Commission. Before, utility workers needed to add chlorine at several points along the transmission lines.

“We had to reboost throughout the sytsem,” Degraca said. “Now we just put chloramine in the water and it’s more persistant.”

Chloramine also forms fewer byproducts, Degraca, and makes water taste less like a swimming pool. “You don’t want to have something too strong,” he said.

“No one wants to smell or taste that.”

Woodburn’s project, including construction, is expected to cost $800,000 to $1.3 million. Proposals to design the system are due Jan. 29, with a winning firm selected Feb. 12.

Construction is scheduled to begin this summer and last four months. Fortunately, Brown said, the treatment plants were built with room to grow, so contractors don’t need to build entirely new buildings.

“They had the foresight when they built these treatment facilities,” he said. “They provided sufficient room for putting in pumps and mixing tanks.”