Nice environment and the grass is applied very good, I like it. But nevertheless you have to keep somekind of shape in your grass mdl and this is a bit time consuming to create, isnt it? Did you tried it with bushes, trees and so on? I really like it. For test-reasons one could create a mdl for the whole level and after finishing one could seperate the mdl for different parts of the map. Additionally you could write code to optimize switching on and off the grass bunches.

Good job.