Residents who live in San Francisco's Hunters Point area filed a $27 billion class action lawsuit against a Navy contractor hired to clean up radiation at the nearby Hunters Point Shipyard.  Tetra Tech is accused of fraud in the radiation cleanup at the superfund site.  Civil rights attorney Charles Bonner annoucned the lawsuit at a news conference...Dozens of families who live in the general area say they've gotten sick from the toxins at the shipyard..[T]hey're blaming Tetra Tech for threats of cancer and other diseases...Earlier this year the Navy found inconsistencies in Tetra Tech's soil sample data and said much of it is likely fraudulent.  Last week, Tetra Tech responded to those allegations for the first time, saying it stands by its work.  A company spokesperson on Tuesday called the lawsuit "factually inaccurate and meritless."