The first time I landed there, back in February, it was also south of the river.
I had researched it on the Washington DOT airports page and realized the actual airstrip was supposed to be north of the river but it was a nice warm day and, as I later learned from the tribal police, there was a subsistence clamming season opener for the local natives.
There were people everywhere on what was supposed to be the landing zone and they didn't look like they were leaving anytime soon - even after I overflew the strip looking for debris and driftwood that might hinder a safe landing.
There is an area a couple thousand feet long just south of the river that is isolated by small streams at each end flowing into the ocean that prevented the clam diggers access. Flat, wide, debris free, firm sand.
Soon after landing the tribal police arrived saying he had a report of a plane going down (which speaks volumes of my landings).
When asked, he verified this was Copalis beach though planes usually land farther north. He had no problem with where we landed and was friendly about the whole thing saying he had to check out any and all reports of planes going down.
We thanked him and he went on his way.