In a project that has both greenfield (dense tree coverage) and previously disturbed (small scale farming) areas, I am trying to determine whether there will be sufficient area to restore 30% of the previously disturbed portion of the site.  The building is sited on both areas (but preserving 40%+ of the greenfield portion).  A rainwater pond is required, which will take up area on the previously disturbed portion of the site. 

The balance of the previously developed portion of the site (what's not building, parking, or rainwater management pond) is less than 30% of the total previously disturbed area.  So I am curious as to whether a rainwater management pond, if landscaped with native/adapted vegetation, could contribute to that 30% restored area calculation. Has anyone ever successfully done this?  Any tips or lessons learned?