After more than half a century at its location on Hansen Way, Communication & Power Industries will soon be asked to leave Palo Alto.

Prodded by years of complaints from the Barron Park residents about the prospect of an "extreme event" releasing hazardous materials into the neighborhood, the City Council agreed late Monday night that it's time for the city to change its zoning laws to prohibit the location of plating shops near residential areas and to begin the process of amortization for CPI, which manufactures microwave and radio-frequency equipment.

The council's 8-0 vote (Larry Klein was absent) followed a new risk assessment that showed that while an event of the sort that can harm residents is very unlikely, it's not entirely impossible. A scenario in which an earthquake ruptures tanks at one of CPI's buildings, prompting the mixing of chemicals and a release of hydrogen cyanide, could harm residents up to 616 feet from the shop. The area includes Chimalus Drive, where residents have been asking the city for nearly a decade to do something about the looming threat from the hazardous materials used by CPI.

The latest assessment followed two prior ones that effectively concluded that a spill at CPI would almost certainly have no effect on the residents. A 2008 study by AECOM considered two different accidents and found that even in the worst-case scenario, the airborne nitric acid and potassium cyanide "are not expected to travel offsite and exceed the toxic endpoint."

Residents argued that these analyses did not consider the "extreme-event" scenario and urged the city to do further analysis.

"It's really not that complicated," said Samir Tuma, who lives on Chimalus Drive. "Fundamentally, what you have is a risk to human life in proximity to residents in the city of Palo Alto. Their lawyer likes to use words like 'very unlikely,' and 'not expected to travel off site.' But you know what? Things that are unlikely do happen."

CPI officials vehemently protested the assertion that their operations pose a risk to health. Bob Fickett, the company's president, said that it's becoming "increasingly difficult to stomach" how the company is being treated like a "pariah" by residents and the city. He noted that in more than 50 years at its present site, not a single resident or employee has been harmed by operations from the plating shop.

"We're not the enemy. We take the health and safety of the community and our employees very seriously," Fickett said.

The company, he said, is willing to continue to "work with the city to an acceptable solution. But like anyone, he added, "we do have our limits."

The council, for its part, sided with the residents, more than 20 of whom attended a discussion that stretched deep into the night. Bob Moss, who lives in Barron Park, was one of many to frame the issue as one of life-and-death and urge the council to begin the amortization process.

"Amortize them out and in six or 10 or 12 years, the safety will be returned to the community because the plating shop will be gone," Moss said. "It's the only safe approach you can take. It's the only sane approach you can take."

The council ultimately agreed, with Councilwoman Gail Price making the proposal to begin zoning revisions to considering amortization. The council should follow staff's recommendation to prepare a zoning ordinance that "protects our communities" and do a "thorough analysis in terms of what is an appropriate amortization period."

Even though the company protested that it has adopted numerous safety measures and plan to further minimize risk, Price and the rest of the council agreed that the very nature of the operation is incompatible with the nearby neighborhood.

Vice Mayor Liz Kniss, a former nurse, recalled an episode in which she took care of two people who were victims of an explosion that caused a chemical spill. One of them did not survive, she said.

"Most of us have agonized over this," Kniss said. "In the end, it comes down to the safety of the people who live in our community and we're in charge of that safety."

Councilman Pat Burt requested that staff go further and research other types of industrial uses, including circuit-board manufacturing and metal etching, that would be included in the new ordinance. His colleagues agreed and directed staff to do further analysis and return with an update at the end of the year.

For residents, the vote was long overdue. Concerns about CPI's operations have been floating around Barron Park since about 2005, when the company was in the midst of consolidating its San Carlos operations in its Palo Alto plating shop and upgrading its facility.

Between 2005 and 2008, the company had three accidents. In 2005, nitric acid was released into the air, creating a noxious odor. In 2008, it was involved in two chemical spills. In March 2008, about 20 gallons of 31 percent hydrochloric acid was released in the company's rear driveway. In May of that year, about 50 gallons of wastewater containing copper and nickel was accidentally dumped into Matadero Creek because of an improper weekend shutdown of process equipment and improper opening of a containment valve, according to staff.

The company, which employs about 660 people at its Palo Alto facility, has since reduced the amount of chemicals processed at its site. Fickett noted that the amount of hazardous materials is now at its lowest level ever. He also noted that the company has taken steps such as adding perimeter sensors, adding alarm systems and installing "backup safety systems."

"We even put in systems that back up our backup systems," Fickett said.

For the council, however, these precautions weren't enough. Mayor Nancy Shepherd joined her colleagues in concluding that it's time to rethink the company's location.

"It's been a long time coming," Shepherd said. "I think the nail on the head for me is that we just don't mix this research-and-development, these hazardous materials, near residents anymore. It's just not how we plan our communities."

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• New zoning law targets Palo Alto plating shops