Rendering of Dam Area's

This adds a fill to the rendering of a Dam.

Before:
![filled_dam_coulter_before](https://f.cloud.github.com/assets/230932/1329590/e95cf2e8-3519-11e3-9a03-1381bb69c244.png)

After:
![filled_dam_couler](https://f.cloud.github.com/assets/230932/1329591/f3b4ea3e-3519-11e3-8578-3e20d445ab20.png)