Two high-ranking Gilbert administrators are out of their jobs after municipal workers halted voter-mandated fluoridation for more than a year at one of the town’s two water-treatment plants.

Public Works Director Lonnie Frost is retiring after 28 years with the town, and Water Manager Chris Ochs has been dismissed, town spokeswoman Jennifer Alvarez said. Both were put on leave last month when town management became aware that a portion of the town’s water supply was not being fluoridated.

The fluoridation system at Gilbert’s North Water Treatment Plant was shut down in July 2011 after officials discovered corrosion in the decade-old equipment, according to internal town e-mails and memos obtained by The Arizona Republic.

Gilbert officials are now scrambling to get the fluoride system up and running and have retained California-based Carollo Engineers to upgrade and repair the equipment. Design work should be complete by the end of the month, Alvarez said.

Construction is expected to take 30 to 60 days once the design is approved, Alvarez said.

The Gilbert Town Council on Thursday also approved a $367,000 contract with CH2M HILL Engineers, a Colorado company that will evaluate all aspects of the town’s water production. Funding for the contract will come from Gilbert’s contingency budget and will not affect utility rates, officials said.

“We’ve had a failure in the chain of command here,” Gilbert Vice Mayor John Sentz said. “We don’t want that again.”

Town Water Department administrators shut down the fluoride system on July 16, 2011, as leaks discovered about three years ago worsened, leaving a white, powderlike substance on the equipment, Frost wrote in a memo. A few minutes of exposure left workers with a burning sensation in the eyes, nose and skin, he wrote.

A month after fluoridation stopped, town administrators brought in several private-sector experts to evaluate the health impacts and test the fluoridation equipment, documents say.

By December, two engineering companies had given Gilbert estimates of about $100,000 to fix the system. But there appeared to be no urgency among town officials to repair the system quickly, and the situation apparently went unreported to upper management for several months.

“It was my call to stop fluoridation until the issues with the room were resolved,” Ochs wrote in an Aug. 15 e-mail to Frost. “(Fluoride) comes into the plant on the raw side naturally, so it’s not like there is no (fluoride) in the water.”

Ochs wrote that he wanted to expedite the process but said he was told to wait until the new fiscal year, which began July 1. When Ochs brought it up at an Aug. 14 staff meeting, officials again decided to wait because fluoridation was on an upcoming Town Council agenda at its annual retreat Aug. 24-25.

On Aug. 22, Gilbert officials publicly announced that fluoridation had stopped at the town’s North Water Treatment Plant, while Frost and Ochs were both put on paid leave.

Fluoride is still being added to water at the Santan Vista Water Treatment Plant in south Gilbert, which is operated through a joint partnership with Chandler, officials said.

While fluoridation to prevent dental cavities has been a subject of public controversy for decades, the U.S. Centers for Disease Control and Prevention has proclaimed it one of the 10 greatest public-health achievements of the 20th century, and every U.S. surgeon general since the 1950s has endorsed the practice of fluoridating municipal water systems.

Critics of fluoridation dispute some benefits attributed to it and worry about potential side effects, such as muscle pain, discolored teeth or bone damage.

The Gilbert Town Council first approved fluoridation in 2000, but a resident referendum forced the issue onto a November ballot that same year. About 54 percent of voters approved the measure.

Shelley Frost, the wife of Gilbert’s now-retired Public Works director, was among the leading opponents of the cavity-fighting chemical.

Gilbert pays about $74,000 a year to fluoridate its water, $70,000 for chemicals and $4,000 for operating costs, according to town documents.

The Gilbert fluoride flap comes at the same time Phoenix officials are reconsidering adding the chemical to its drinking water. A City Council subcommittee is set to meet Tuesday to discuss the options.