The Puget Sound in Washington state and waterways in San Diego will be the test sites for a new Department of Homeland Security pilot program to test small vessels for radiological devices and materials.

DHS says [1]:

The three-year pilot program involves the development of a radiation detection architecture that reduces the risk of radiological and nuclear threats that could be illegally transported on recreational or small commercial vessels. The pilot will be conducted in close coordination with the U.S. Coast Guard and Customs and Border Protection.

Smalls vessels are designated by DHS as any watercraft less than 300 tons and include "commercial fishing vessels, recreational boats and yachts, towing vessels, uninspected passenger vessels, or any other small commercial vessels involved in foreign or U.S. voyages."

San Diego's Channel 10 News reports [2]:

 According to the DHS, about $10 million will be spent on the pilot program to purchase radiation detection equipment, including portable sensors and fixed-position detectors 

It is intended to counter the risk of radiological and nuclear threats that could be illegally transported into the country on recreation or small commercial vessels, according to the DHS.

 The pilot program is another layer of security to plug gaps left by the 2002 Maritime Transportation Security Act [3], which allowed security checks of large commercial boats and yachts over 300  tons.

 While the program is already underway in the Puget Sound, DHS will not say specifically when the program will begin on San Diego waterways other than "soon."