A proposed data center on the Alameda waterfront boasting of benefits to the environment through the use of bay water to cool its banks of computer servers, was flatly rejected by the Alameda City Council Tuesday night.

In recent months, opposition from city officials and the public toward the proposal by Nautilus Data Technologies had steadily risen. The company was seeking a 15-year lease for three buildings near the bay on West Oriskany Avenue at Alameda Point.

Tuesday night’s decision included unanimity for turning away the proposed data center, a rare accomplishment in a city known in recent years for its notoriously fractious political landscape.

Nautilus Data Technologies had sought to rehabilitate roughly 86,000 square feet of space at the former Alameda Naval Air Station for the data center. At the site they planned to employ an untested method of cooling computer servers, which can become extremely hot and therefore an energy hog through its reliance on air-conditioning.

Water was to be pumped from one portion of the bay through a 60-inch pipe. After it is circulated through the building, the water would then be discharged back into another portion of the bay, and nominally heated, according to the applicant. The project was portrayed as a novel and an environmentally-friendly solution for lowering the servers’ temperature.

But as environmentalists and the members of the public joined the discussion, questions over the proposal’s impact on the bay grew louder. Concerns over potential algae blooms due to localized warmer water, and other impacts to the existing habitat gained prominence. In addition, the use of so-called “once-cooling” technology is also outdated and has already been banned by the state for use by power plants, critics added.

“All we’re asking is to move on to the next step,” Nautilus Data Technologies CEO James Connaughton said Tuesday night. If the lease was approved, Nautilus Data Technologies would still be required to obtain up to a dozen required permits before it could move forward with its plans. Connaughton added, approving the lease at this point in the process posed no risks to the city or environment. “Either we pass muster, and there’s no environmental impact, or we don’t, and there’s no environmental impact.”

Alameda officials, in rejecting the proposal, potentially left up to $25 million in revenues on the table for the city’s utility, Alameda Municipal Power, said Mayor Marilyn Ezzy Ashcraft. “Money isn’t everything,” she added, fearing the impact on the bay outweighed potential financial benefits to the city.

The council met with Connaughton in numerous closed sessions meetings since last year, Ashcraft said. During these conversations, Connaughton failed to sufficiently answer numerous questions about the data center’s environmental impacts, she asserted.

A letter from San Francisco Baykeeper, an advocacy group, however, was far more persuasive. In the letter, Baykeeper laid out a panoply of potential problems with the proposal, primarily the increased temperature of water flowing back into the bay from a discharge pipe.

Connaughton had made public comments that the temperature of water leaving the data center would increase by just one-tenth of a degree Fahrenheit. But even that sort of localized temperature increase would greatly affect aquatic life around the discharge site, Baykeeper told the council.

There was also clear dissatisfaction expressed by councilmembers with Nautilus Data Technologies’ inability to modify its proposal despite repeated questions over the data center. “What I haven’t seen is a change in the approach,” Ashcraft said.

One response from the applicant included a nearly 15-year-old study that found toxic algae growth was unlikely in San Francisco Bay because of the turbidity of the body of water. Ashcraft said the study and the science behind it is likely outdated. “Nothing I’ve seen at this point is aligned with my values at Alameda Point,” she added.

Councilmember Tony Daysog also indicated he wanted better examples from the company assuring him the project was safe for environment, but he received none.

“Protecting means we don’t open up our bay to laboratory experiments,” said Councilmember Jim Oddie, perhaps the most consistent voice in opposition to the data center. “This is too risky for me.”