Multiple Building Applications

I've seen this particular scenario several times, both as a reviewer and project lead, and the best option is to divide up the centralized campus-wide data by some building specific metric like gross floor area or regular building occupants. This way, you can describe the weighted portions of purchasing and waste management data that are attributed specifically to the buildings that are seeking certification. Make sure to include a detailed, thorough narrative explaining that you are using a campus approach and describing the methodology (and datapoints) used to derive the weighted buidling-specific amounts.

Just to add to this - purchasing and waste (although not all credits in either category, prominent exceptions being mercury-containing light bulbs and the waste audit) are two areas where USGBC/GBCI has in years past shown a willingness to accept campus-wide information, particularly in instances where a single entity (a university for example, or single company, in contrast to a multi-tenant office park) occupies the entire property. The key is that the buildings included in the campus share enough characteristics so as to safely conclude that campus-wide performance is fairly representative of all buildings, and that the building being certified is not likely to be a starkly negative outlier in the group. Positive outlier they can live with, negative, not so much.