Complex sentence: Both sites are now mostly submerged by the Tellico Lake impoundment of the Little Tennessee River, the exception being the Chota townhouse site, which was raised above the reservoir's operating levels and connected via causeway to the mainland.
Split into simpler sentences: Both sites are now mostly submerged by the Tellico Lake impoundment of the Little Tennessee River. The Chota townhouse site was raised above the reservoir's operating levels and connected via causeway to the mainland.