Navigation in web app with wide tables

What is the best approach for choosing main navigation for a web app, when:

• most of the views are very wide table/grid
• the number of menu items is around 10 or more (and might grow)
• 2nd level of navigation might be necessary for some items
• we talk about enterprise app, users will use it in their daily work routines

The dominant approach now is to use the dashboard-style, vertical navigation on the left, but I am concerned about the screen real-estate.