According to documents recently obtained under the Freedom of Information Act, Google's plan to show off its technology in special floating showrooms was scuppered late last year when the barges used in the project were deemed unsafe.

The mysterious barges appeared around the country in the latter half of 2013, with one in San Francisco, and one in Portland, Maine. After much speculation about their purpose, a Google spokesperson confirmed in November last year that it was exploring using the barges as "an interactive space where people can learn about new technology," such as its augmented reality Glass wearable. But at that point, The Wall Street Journal reports, the project had already been on hold for two months after the US Coast Guard repeatedly raised fire-safety concerns that Google was unable to satisfactorily answer.

"Over 5,000 gallons of fuel on the main deck."

The documents obtained show that the Coast Guard had significant questions about Google's plan at every stage of its development. In an email sent in March 2013, Robert Gauvin, the Coast Guard's acting chief of commercial vessel compliance, warned that the barges would have "over 5,000 gallons of fuel on the main deck" alongside a "substantial amount of combustible material." In August, the Coast Guard wrote that the boat's designs didn't incorporate "certain fire safety features typically required," and said that it could not ascertain whether Google's contractor had made provisions for the evacuation of disabled people. In September, a Coast Guard inspector reiterated that more safety measures were needed.

Google said it expected 1,200 people would visit the San Francisco showroom every day, but Foss Maritime, the contractor building the barges, said no more than 150 would be on board at the same time. Gauvin questioned this number in a March email, in which he said he was "unaware of any measures you plan to use to actually limit the number of passengers," and expressed his concern that "significant work has already been performed without full consent of the Coast Guard."

Some Coast Guar dofficials signed non-disclosure agreements with Google

The Wall Street Journal reports that some Coast Guard officials signed non-disclosure agreements with Google to keep the barge's purpose secret, a decision the government body later lamented. "In hindsight we should have sought legal review earlier," said one captain in an internal mail to a group of officers. The tech giant also tried to get government officials on side, offering National Park Service managers a tour of the showroom that began with a journey in "a special Google speed boat."

Despite Google's best efforts to convince the relevant officials, the fire risk was apparently too high for the project to continue. Google was ordered to move its San Francisco barge in February this year, and dismantled and sold the Portland barge for scrap in August.