Okay, I lied... no answer today. I forgot I did have one useful photo of my own that may help clarify the origin of the wall. Below is an annotation to draw your attention to the important bits.
That darker rock above the hammer head should be a dead giveaway. The small bit under the oval to the right is similar. And the arrows emphasize the color gradient I was hoping someone might notice in the last two days' pictures. Another thing that may help: this is Tyee Formation, which usually weathers quickly. While this outcrop is at least 25 or 30 years old, corners and edges are still sharp and fresh. Cuts of similar age elsewhere in this unit would be quite punky. Answer tomorrow, I promise. There aren't any more clue photos; the only one left has the answer.
Photo unmodified. May 6, 2013. Location uncertain, but maybe here.