Site Boundary Including Other Structures

We are certifying a ~30K sf building that shares its site (legal parcel) with a large 8 story garage. The two structures are being designed and built on a similar timeline but ultimately the garage does not serve the building, it just happens to be adjacent to it. USGBC confirmed that the garage should not be included in the LEED project. If you can picture the layout: small, certifiable building in question is to the east, garage is directly west and the detention pond for the site is southwest of the garage. How should we draw our project boundary? We would like to include the detention pond as it provides stormwater control for the whole site and would make us eligible for another point. Is it reasonable to draw the boundary around the whole parcel, with a hole in the middle where the garage would be? Can we then exclude the garage from open space/hardscape calculations? Curious to see what your experiences are.