NEW YORK (AP) — New York City Mayor Bill de Blasio is announcing a plan to protect lower Manhattan from rising sea levels by surrounding it with earthen berms and extending its shoreline by as much as 500 feet.The Democratic mayor was to announce the plan Thursday after previewing it in New York magazine .Officials have been developing schemes to fortify New York City's waterfront ever since Superstorm Sandy destroyed thousands of homes and businesses in 2012.