Taking into account existing greenbelts and waterways, Johnson City’s planning commission is expected to vote soon on one of two key rules that will guide the future of development in the city.The ordinance would require at least 15 percent open space in most new residential developments. At least half of the space would be called “active space,” meaning it would be usable as something like a park, playground, or garden. The other half could simply be empty land, forest, a creek or storm water area.