Saltwater Intrusion & Hilton Head’s Response
The water supply coming from our Upper Floridan wells continues to be threatened by saltwater intrusion. Extensive scientific research conducted by the states of South Carolina and Georgia, the U.S. Geological Survey and the PSD have shown that the intrusion is advancing at a rate of about 400 feet per year across Hilton Head and all Upper Floridan wells on the island will eventually be lost to the intrusion. The PSD has lost six of its 12 Upper Floridan wells since 2000 and anticipates losing five of the remaining six wells by 2024.
Studies and monitoring have shown that the over-pumping of this aquifer in the Savannah, Ga., region has reversed the flow of the groundwater bringing saltwater from Port Royal Sound into the Upper Floridan Aquifer at Hilton Head Island. Some naturally-occurring plumes of saltwater also have impacted the Upper Floridan.
Hilton Head Island’s withdrawals from the Upper Floridan Aquifer have been capped by the State of South Carolina since 1997. In that same year, Hilton Head and Broad Creek PSDs spent $16 million to construct a 24-inch water supply transmission line and related distribution equipment to bring treated Savannah River surface water to the island. The PSD’s RO Plant and ASR well were needed to replace water supply lost as a result of saltwater intrusion into the Upper Floridan. The island’s three PSDs estimate that they have collectively spent $129 million combatting saltwater intrusion since 1998 – including the development of alternative water supplies and purchasing more treated Savannah River surface water. The three utilities estimate that another $80 million may be spent in the next 20 years to continue replacing lost supply.
Saltwater Intrusion Timeline:
- 1995 – South Carolina Department of Health and Environmental Control (DHEC) declares capacity use zone.
- 1999 – Pipeline from mainland provides treated surface water.
- 2000 – PSD begins losing wells to saltwater intrusion.
- 2004-2006 – PSD undertakes series of feasibility studies to determine alternative supply options.
- 2009 – PSD opens its Reverse Osmosis (RO) Water Treatment Facility at 3 million gallons per day (mgd) capacity.
- 2011 – PSD builds island’s first-ever Aquifer Storage & Recovery (ASR) Facility to provide 2 mgd during spring/summer demand.
- 2015 – PSD adds 1 mgd capacity at RO Facility, bringing total RO capacity to 4 mgd.