Existing Irrigated Turf Area

Our project will add a building to a large existing master planned area. Our scope of work will add new drought tolerant plantings and irrigation to our small part of the bigger site, but there is also existing turf grass with existing irrigation nearby. If the turf grass area is included in our LEED boundary, are we obliged to include the existing turf and its irrigation in our outside water reduction calcs? Or can we exclude this irrigation? Would we actually be required to retrofit existing irrigation?