As I mentioned yesterday, this was a basalt quarry, the rock presumably crushed for road gravel. The trench was roughly parallel to the coastline. When it was retired, BLM, which manages Yaquina Head, decided to breach the western end to the shore, allowing waves and tides free entry to the quarry. Then, building a series of ramps and walkways, they would create a unique handicapped-accessible set of tidepools and all the fascinating lifeforms therein. It sounded great in theory, and truly was a clever and well-intentioned idea, but they should have a geologist- any geologist, really- look over the proposal and site before implementing it.