Description: These data represent federal and state lightering zones within U.S. waters. Lightering is the transfer of a cargo of oil in bulk from one oil tanker less than 150 gross tons to another oil tanker less than 150 gross tons, or a cargo of hazardous material in bulk from one vessel to another. Lightering is often used to reduce vessel draft prior to entering a port. A lightering zone is an area were lightering is either designated, prohibited, has traditionally occurred, or where restrictions are in place to ensure or constrain lightering activities.