The type of irrigation that can be assigned to certain vegetation types is pre-determined in the calculator, limiting user ability to make adjustments that might better reflect the design conditions. This is likely based on EPA’s assumptions about potential changes to the irrigation system and future use. GBCI has not provided a work-around for this yet, so if you are concerned about the methodology not accurately reflecting project conditions to a degree that impacts your ability to meet the prerequisite, consider submitting a CIR and proposing an alternative compliance path.