Henry...I found the Transition Area Guidelines. However, there is nothing mentioned about any ratio of developmental land to undevelopmental land. The only thing close, to what you were saying, is mentioned only in the 70db Noise Zones and that is that 50% of the entire project is to be used for amenities, non-residential and conservational purposes. This is just as I stated. The entire project is used to figure the number of residential units, including non-developmental land, such as lakes and sand-pits. However, from what I understand, Sherwood Lakes is not in any noise zone. Therefore, the 50% clause does not pertain to this project, but other amenities do, such as waterways, lakes/pits and pedestrian/bike trails.
Here is where the guidelines are located (They are from pages 15 to 22):http://vbgov.com/dept/planning/vgn_files/policy_ch5.pdf