Scene Practice 4 - Hoover Dam

This is the Hoover dam on the Colorado river, between Arizona and Nevada, USA.
I painted this from photographic reference.

This work is part of my Drawing class project aimed at improving on composition and rendering of environmental concept art.
As you might already know, I wasn't very pleased with my previous attempts at creating scenes.
I wasn't able to convey the right sense of scale and atmosphere [link] or it lacked gravely in my portrayal of depth [link]

The reason for drawing from photographic reference first is because it's a real-life example and all the details are there.
When drawing from a basic 3D layout model, all the reference I'll have would be the composition of basic shapes...