We use lot size, original structure, and additional hardscape (30% remaining area). The District estimates irrigated landscaped area by using information from the San Bernardino County Assessor’s Office. We take your lot size, then subtract the square footage of the original dwelling structure built on the property, and then subtract 30% of the remaining area for additional hardscape (additions, garages, driveways, sidewalks, etc.). The result of that calculation is your estimated irrigated landscape.