...

"Presuming the image accurately reflects the coloration and surface texture of the specimen, I'd definitely go with C. taedatus. In general, if a specimen from around here is all black, with no hint of metallic reflections or copper/purple/red/green hues and has a dull surface, that's C. taedatus: C. nemoralis is always shiny with metallic reflections and hues. Other characteristics are shorter and narrower posterior pronotal angles (the pronotum itself is substantially narrower than in C. nemoralis) and much more distinctly ovate elytra that are much narrower anteriorly than at the widest point. The interstriae between the foveate interstriae are thinner, more linear, and less interrupted than in C. nemoralis. As I recall, Gay Hunter Edelbrock raised at least several of the subspecies to full species rank in her thesis, but I don't believe that information has been published and thus the status quo is that everything treated in Hatch as C. taedatus remains that way.
"I've found this to be a sporadically common species in the Puget Trough and Willamette Valley and quite common east of the Cascades."