AT&T ran into an insurmountable problem: Napa’s utility poles, most jointly owned with PG&E and AT&T, are too short.

This fatal deficiency wasn’t known when Napa and AT&T inked their Wi-Fi agreement with much fanfare in February, officials said.

The California Public Utilities Commission subsequently issued new regulations spelling out how Wi-Fi antennas can be attached to utility poles.

When new safety clearances for high-voltage lines were added up, there wasn’t enough room on Napa’s 30-foot poles for Wi-Fi, said Damon Wei, AT&T’s general manager for Napa. “You have no room left to install anything,” he said.

Nothing can be hung on the bottom 16 feet of a utility pole, Wei said. That leaves just 14 feet on a 30-foot pole for up to two levels of electrical lines. The Wi-Fi devices would have intruded into the PUC’s mandated safety zone, he said.

AT&T had planned to place 2-foot-high antennas the shape of small beer kegs on the arms that hold city street lights. In the first phase, nearly 100 of these devices would have blanketed 2 square miles of the core city, with coverage for another 2 square miles occurring later.

Anyone with a Wi-Fi-enabled computer would have been able to log onto the Internet from parks, backyards, moving vehicles and, with boosters, inside buildings.

The Police Department, which helped negotiate the deal with AT&T, planned to use Wi-Fi to upgrade communication between headquarters and officers in the field.

Officers would have been able to transmit video, receive thick reports and photos and stay on patrol for more hours each day.

“We’re extremely disappointed,” police Cmdr. Jeff Troendly said Wednesday. Looking ahead, police may seek partners for a smaller Wi-Fi system that serves downtown and the Oxbow District, he said.

The AT&T system had other municipal uses. Water meters could have been read automatically. Building inspectors could have tapped into city data bases while doing inspections.

This is a major disappointment, said Bob Quinn, the city’s Wi-Fi project manager. AT&T had designed Napa’s wireless system and was ready to install it when the seriousness of the new Public Utility Commission rules became apparent, he said.

The city is out some staff time, but not much else, said Barry Martin, the city’s community outreach manager. “We let AT&T take the risk. We knew we did not want to put money into this deal,” he said.

Nearly 100 cities nationwide have saturation Wi-Fi coverage, but many high-profile projects have failed due to uncertain economics and regulatory complications.

The nearby city of Concord installed Wi-Fi antennas on some of its utility poles, then had to remove them after the new Public Utility Commission regulations were issued, Quinn said.

San Francisco teamed up with Earthlink for a citywide Wi-Fi system, then Earthlink pulled out similar projects nationwide, saying it needed to rethink the economics.

In Napa, AT&T would have offered free Wi-Fi with advertising up to 10 hours a month. Faster, unlimited, ad-free service would have cost about $20 a month.

The city would have received 50 Wi-Fi accounts for free, with police using most of these connections. These accounts were valued at $450,000 over the five-year life of the agreement.

With citywide Wi-Fi, Napa would have had an amenity to attract and retain businesses, while also serving tourists who are looking for information on places to visit and dine, officials said.

Although the Napa project isn’t feasible, AT&T is pursuing pilot programs with three other cities: Riverside, St. Louis and San Antonio, Wei said.

Riverside owns its own light poles. Because they do not carry electrical lines, they are not covered by the same Public Utility Commission restrictions that killed the Napa project, he said.

AT&T continues to be a major provider of broadband Internet service in Napa through its phone lines. Wi-Fi is available at many “hot spots,” including cafes, hotels and public spaces, including the city library.

If the deal with AT&T had succeeded, all of Napa would have become a giant hot spot.

If the technology changes, AT&T may be back with another Wi-Fi proposal, said Paul DiGiacomo, AT&T executive director of new services development. “We’ll have to wait for Wi-Fi on steroids when you need less assets per square mile,” he said.

In that case, there might be enough city-owned light poles without electrical lines to support city-wide Wi-Fi.