The Ashepoo Combahee Edisto Basin National Estuarine Research Reserve (often shortened to ACE Basin NERR) is a 140,000-acre (570 km²) reserve area located in the ACE Basin, one of the largest undeveloped estuaries on the Atlantic coast of the United States. It is named for the Ashepoo, Combahee and Edisto Rivers, which meander past cypress swamps, historic plantation homes, old rice fields and abundant tidal marshes to meet at South Carolina’s biologically rich St.