As a tectonic shift in state wastewater regulations is under consideration by state officials, Island homeowners and towns are bracing for what could be millions of dollars in mandatory upgrades in the coming years.

On a boulder-peppered hill in Chilmark, a septic system is near completion. Tons of dense clay have been excavated and in its place a mess of tubes and concrete boxes now sit. Only one step is left: the septic must contend with Coop.