Charlestown falls within the Salt Pond Critical Resource Area, covering watersheds that drain to Ninigret Pond, Green Hill Pond, and Watchaug Pond. RIDEM does not permit conventional drainfields in this area — any new install, repair, or replacement requires an advanced nitrogen-reducing system. We install Geomatrix GST, Orenco Advantex, Eljen GSF, and Bottomless Sand Filter systems approved for this designation.