Updated

OLYMPIA, Wash. -- The next devastating earthquake to strike off the Northwest coast is expected to send a tsunami so fast that it could leave coastal communities with perhaps 20 minutes to escape the surge of water.

Coastal towns without accessible high ground are now closely examining the construction of large structures or mounds that could provide people a chance to escape in time. The so-called vertical evacuation sites have been adopted in parts of Japan but have never been pursued in the United States.

Communities in Washington have identified a series of about 40 potential evacuation sites and are now working on more for areas on the Olympic Peninsula. Officials say the projects are in the conceptual stages and that it could be difficult to raise money to build them.