The Navy discovered the elevated levels of radiation in Unit F of building 1303, which is unoccupied, NBC Bay Area reported. The Navy once used the man-made San Francisco Bay island as a base and is responsible for cleaning it up before Lennar Corp. builds 8,000 homes there.
Radiation in the home is above normal background levels, but well below the threshold to cause health problems, the Navy said. The radiation "equates to an expected annual dose of no more than" 5.5 millirems, according to the Navy.
By comparison, a roundtrip cross-country flight exposes a passenger to 3.7 millirems of radiation, the Navy said.
So far, the Navy has performed radiation tests on 325 of the existing 600 residential units on the island. It plans to finish testing by September.
Radiation may stem from ships that were exposed to nuclear weapons testing in the Pacific Ocean, according to the Center for Investigative Reporting, which first reported that the Navy had underestimated contamination on the island.
Treasure Island is part of San Francisco, and The City paid the Navy $103 million for it in 1993. The Navy could begin transferring ownership rights of the island to San Francisco as soon as this year.
About 2,500 live on Treasure Island. Another 500 people work there in the winemaking and film production industries.
Building the new neighborhood for 20,000 people on the island, which will include high-rises as well as commercial spaces, could cost as much as $1.5 billion.