What is the smallest practical planning unit for environmental engineering controls?

In the context of environmental engineering controls, the smallest practical planning unit is often considered to be the community. Communities can vary in size but are generally more localized than counties, states, or districts. They represent a specific population that can benefit from targeted environmental controls and regulations that address local issues such as waste management, water quality, and air pollution.

While counties and districts are larger administrative areas that may implement broader policies and regulations, they do not typically focus on the specific, immediate environmental concerns of a smaller area. The state level can establish overarching laws and regulations, but it is often too large to address local concerns effectively without the input and implementation at the community level. Thus, community-level planning allows for more tailored solutions that meet the unique needs and conditions of the local environment and population.