I am about 90 minute drive to the beach (Seaside).
When I go to Newport, I go clamming with bare feet. I can feel the cockles through the mud and there is no random digging. Were you at the Hatfield marine center?
There are some ok coast trails, but if you want some of the best head further north to the Olympic NP coastal section or Pacific Rim NP on Vancouver Island. I have backpacked the Olympic coast and you have to plan around the tides as some sections are only passable at low tide.
