Here goes.
http://dl.dropbox.com/u/458143/goldrock/cp_goldrock_gulch_b20000.jpg
I particularly dislike this room/these rooms with the planking (overall, I don't like the brush-plank-destruction). Textures aren't aligned right and the floor would be just as good dirt instead of being the same texture as the walls.
http://dl.dropbox.com/u/458143/goldrock/cp_goldrock_gulch_b20001.jpg
This barrier doesn't look right and clips through the right side of the truss. The way the cart track swerves through it at the right edge makes the whole doorway look illogical, center it on the track or remove that area altogether.
http://dl.dropbox.com/u/458143/goldrock/cp_goldrock_gulch_b20002.jpg
I'm not sure why that arrow is necessary. Another example of white wood wall white wood floor texturing combination. Brown wood works so much better for floors, especially when combined with white walls. And that texture you keep using as a floor is most definitely a wall texture.
http://dl.dropbox.com/u/458143/goldrock/cp_goldrock_gulch_b20003.jpg
Adjust that displacement a bit so that nodraw isn't visible.
http://dl.dropbox.com/u/458143/goldrock/cp_goldrock_gulch_b20004.jpg
Corrugated metal would never be cut into strips like that, and this is another example of that destroyed-planking-style that just doesn't look good.
http://dl.dropbox.com/u/458143/goldrock/cp_goldrock_gulch_b20005.jpg
Odd choice of texture for the roof and the barrier. Another appearance of white wood wall as a floor. Corrugated metal walls on top of a (vertical) white wood wall is weird.
http://dl.dropbox.com/u/458143/goldrock/cp_goldrock_gulch_b20006.jpg
Floating crates. Odd place to store stuff.
http://dl.dropbox.com/u/458143/goldrock/cp_goldrock_gulch_b20007.jpg
You have a nice detail area covered up by destroyed-wood-planking-style. Replace it with chicken wire and put some crates and wire spools and let that area be visible. Also, there is a mining light back in there that you can't see, and unnecessary prop_dynamic.
http://dl.dropbox.com/u/458143/goldrock/cp_goldrock_gulch_b20008.jpg
The two conveyors stacked on top of each other looks bad. Also, your skybox ground is clipping into the world back there, causing extremely dark shadows on the displacements. Furthermore, what is that light supposed to be lighting?
http://dl.dropbox.com/u/458143/goldrock/cp_goldrock_gulch_b20009.jpg
Not a good texture to represent a boarded up tunnel. Either change it or remove that truss and texture altogether. And a wooden sign stuck into a wooden floor? And look at the texturing on those stairs.
http://dl.dropbox.com/u/458143/goldrock/cp_goldrock_gulch_b20010.jpg
Door could use a trim. More white wood wall as flooring.
http://dl.dropbox.com/u/458143/goldrock/cp_goldrock_gulch_b20011.jpg
Not a great choice of texture for a trim. Levitating minecart.
http://dl.dropbox.com/u/458143/goldrock/cp_goldrock_gulch_b20012.jpg
That board could be the arrow sign prop (trainyard_sign I believe)
http://dl.dropbox.com/u/458143/goldrock/cp_goldrock_gulch_b20013.jpg
White wood wall as destroyed-plank-style flooring. Could remove all of the planks, make the displacements prettier, and save faces while massively improving the visuals of this area.
http://dl.dropbox.com/u/458143/goldrock/cp_goldrock_gulch_b20014.jpg
Any particular reason the bottom of the canyon is in the world? Just creates odd problems with the fog in relation to the skybox.
http://dl.dropbox.com/u/458143/goldrock/cp_goldrock_gulch_b20016.jpg
Odd optimization, rendering the middle point from the 3rd/4th/whatever it is.
http://dl.dropbox.com/u/458143/goldrock/cp_goldrock_gulch_b20017.jpg
Floating carts + white wood planking + poor choice of textures for that shack.
Overall, I love the idea of this map, a large scale battle with shifting areas of control, however, navigation is odd, and the detailing seems poorly done (especially in regards to texturing- Valve maps are great references for texturing, and they're included with the SDK!).