The Washington Dental Service Foundation has sent a letter to the city of Bellingham promising to pay the startup costs if voters approve fluoridation this November.

The Seattle-based organization “would like to formally confirm our commitment to the citizens of Bellingham for financial assistance up to $600,000 for construction and implementation costs associated with a fluoridation project for your city, if approved by voters this November,” wrote Tracy E. Garland, president and CEO of the foundation in a letter to Mayor Mark Asmundson Wednesday.

Foundation officials hope the letter will put to rest the question of whether the grant would materialize if voters approve fluoridation, said Sean Pickard, the foundation’s manager of governmental relations.

A lawyer representing Citizens Against Forced Fluoride wrote to the City Council earlier this week, saying the initiative was illegal partly because it depends on funding from a private source outside the city’s jurisdiction.

The $600,000 is based on an engineering study completed this spring, examining what it would cost to begin fluoridating the city’s water supply. The study estimates annual operating costs would be $33,000.

But those opposed to fluoridation have said it would likely cost more, citing how much it would have cost the Lakewood Water District to fluoridate its water supply.

That district found that it would have cost $140,000 annually to fluoridate its 70,000-user water system, and was facing startup costs of nearly $1 million, said Christy Butler, executive assistant to the Lakewood district’s general manager.

But Lakewood, with 31 well water sources, has a different kind of water system than Bellingham, which has a single source, Lake Whatcom. Engineers told the Lakewood Water District it would have had to remodel 17 of its 31 well sites, Bell said, which would have boosted startup costs.