Concerns about the U.S. Navy's commitment to cleaning up contaminants on the polluted Hunters Point Shipyard prompted several state legislators to write city leaders a letter earlier this month.

Assemblymembers Tom Ammiano and Fiona Ma and state Sen. Leland Yee signed the letter, which expressed particular alarm about one polluted parcel on the 500-acre shipyard.

Developer Lennar Corp. is working with the city to remake the former Navy base and Candlestick Point into neighborhoods with 10,500 housing units, retail and commercial development, parks and possibly a new football stadium.

One plot has been cleared for development and condos and apartments could be built there by mid-2011. Another, intended for the potential stadium site, could be done as early as 2010.

Because the shipyard is designated by the U.S. Environmental Protection Agency as a toxic Superfund site, the Navy must clean individual pieces there before turning them over to the city.

The federal government designated $81.6 million for cleanup for the upcoming fiscal year, but the price tag for making the entire shipyard safe is $300 million to $500 million.

The Navy is reviewing four alternatives for cleaning one very nasty spot, known as Parcel E, which was the scene of repeated underground fires in 2000. They strategies range from completely removing the soil to placing a protective cap over it.

Michael Cohen, who overseas development projects for the city, said that a final choice would have to be certified by state and federal regulators before it was accepted by the city.