If the Portland City Council decides to add fluoride to local drinking water, it should prepare for three things: sizable costs, big-time opposition, followed by a half-decade wait.

Putting fluoride in Portland, Gresham, Tigard and Tualatin’s water supply would require “significant” project costs of about $5 million and ongoing operations and maintenance expenses of $575,000, according to city estimates obtained by The Oregonian.

From there, it would take at least five years to get the fluoridation facility up and running.

And that, of course, would happen only if the whole plan survives politically: “Implementation of fluoride would likely be challenged by the public,” according to a city memo.

The costs and analysis are included in three single-page documents prepared by the Portland Water Bureau this summer and obtained by The Oregonian through a public records request.

According to the documents, representatives from the Centers for Disease Control and Prevention and Upstream Public Health (which is pushing the effort locally through the newly created Everyone Deserves Healthy Teeth Coalition) met with the Water Bureau on May 10. A month later, the Water Bureau provided the cost information to Mel Rader, a co-director at Upstream.

The Water Bureau puts costs for a fluoride facility at $4.95 million, although officials acknowledge that the project could run from between $3.5 million and $7.6 million because so little has been planned. Those estimates are in 2012 dollars, meaning the actual cost would increase because of cost escalation for the multi-year project.

City estimates included three cost estimates, one for liquid and two dry fluoride options. But officials wrote that any fluoridation project would have to use liquid, or fluorosilicic acid, because dry fluoride options “are not feasible for large utilities due to the frequency of chemical handling and fluoride dust exposure associated with the chemical handling.”

The actual facility would cost about $2.4 million but pilot testing, soft costs and project contingency push the tab to about $5 million. But officials note that adding fluoride would likely change pH levels in the water and “would require additional caustic or other corrosion control chemical to bring the pH back up to an appropriate level to control corrosion in the distribution system.”

“The cost of any additional capital improvements needed to mitigate water quality impacts are not included in the estimated capital costs,” according to the memo.