Island’s fresh water supply shouldn’t be taken for granted

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Pete NardiPublic tap water is a dramatically undervalued commodity. A gallon of tap water on Hilton Head Island costs literally a fraction of a penny – delivered on demand 24/7, 365 days a year. Consider that cost per gallon versus other products you regularly buy. Tap water is so undervalued nationally that we’ve taken our public water infrastructure for granted. A recent study by the American Water Works Association estimated that more than $1 trillion is needed over the next 25 years to replace worn out water infrastructure in the U.S.

Hilton Head is ahead of that curve, but it has come at a cost. The island’s water utilities have invested more than $130 million since the late 1990s to develop alternative water supplies as a result of salt water getting into the fresh water wells that had been the island’s traditional source of public tap water. The result has been the provision of a high-quality, long-term, abundant water supply for the island.

On average, Hilton Head Public Service District supplies 5 to 6 million gallons of tap water to island residents a day. The district’s peak demand — 10 to 11 million gallons a day — usually occurs for one or two days in July. The water utility has a total capacity of 12 million gallons a day, and it has the ability to buy even more water on a wholesale basis from the mainland if needed.

On Hilton Head, we are blessed with multiple sources and supplies of water, which allows us to select the most economical options based on demand. Our most expensive source of tap water is the water we buy on a wholesale basis from the mainland at a cost of $1.78 per 1,000 gallons. The service district’s reverse osmosis drinking water treatment facility provides 4 million gallons a day of tap water — more than 45 percent of the island’s water supply. Reverse osmosis water is produced for 73 cents per 1,000 gallons. The least expensive water source is the fresh water wells we are losing to saltwater intrusion, at 19 cents per 1,000 gallons.

There are some really important facts about tap water and recycled water on Hilton Head that we all should bear in mind:

  • Hilton Head has experienced a 9 percent drop in tap water consumption since 2013. This follows a national trend that has seen a 22 percent drop in indoor water use since 1998.
  • About half of the demand for tap water on the island is used for irrigation of residential and commercial landscaping.
  • Residential and commercial irrigation is limited by town ordinance to two days a week at all times.
  • The town ordinance also requires all irrigation systems to have a working rain sensor.
  • All of Hilton Head’s wastewater treatment plants are 100 percent recycled water operations. That means we don’t treat and then discharge wastewater to any area bodies of water. Instead, we recycle the water into golf course irrigation water or water to nourish vital and rare wetland habitats. My utility alone recycles about 1 billion gallons of water a year.

Now let’s take a brief look at our sources of tap water.

REVERSE OSMOSIS

The reverse osmosis facility draws raw water from the brackish Middle Floridan Aquifer, about 600 feet deep. It then uses a pressure-driven membrane separation process that removes ions, salts and other dissolved solids and nonvolatile organic compounds. The membranes are comprised of synthetic polymers similar to nylon. The polymers are permeable by water but reject particulate matter such as salts and other minerals. The process produces fresh tap water and yields a concentrate of the rejected solids. For every 4 million gallons a day of tap water produced by the plant, 1 million gallons a day of concentrate is diffused into the saltwater background of Skull Creek via a pipeline at the end of Jenkins Island Road. This process is the same process used to make brand-name bottled waters such as Dasani and Aquafina — but you get it delivered to your kitchen faucet.

WHOLESALE WATER

We purchase water on a wholesale basis from the Beaufort-Jasper Water & Sewer Authority. It is processed and purified at BJWSA’s state-of-the-art surface water treatment plants in Chelsea and Purrysburg. The purified water then enters the Hilton Head service district’s water storage tanks and distribution lines via a large pipeline located beneath the Intracoastal Waterway. Wholesale water provides about 25 percent of our water supply.

AQUIFER STORAGE & RECOVERY (ASR)

The service district constructed the island’s first-ever aquifer storage and recovery (ASR) facility in 2011. The facility stores treated wholesale tap water that is purchased in the winter months, when demand is low, at a less-expensive, “off-peak” wholesale rate. It then withdraws and retreats that water during the summer months of high demand and the full wholesale rate. The ASR facility provides 2 million gallons a day of tap water during the summer, accounting for about 12 percent of our total water supply.

FRESH GROUNDWATER WELLS

The Upper Floridan Aquifer is a limestone, fresh water aquifer located 50 to 150 feet underground. It is one of the largest aquifers in the world, and stretches from the Beaufort area south through the Florida Everglades. Fresh water from this aquifer requires little treatment. The Hilton Head service district uses automatic feeders that supply precise amounts of chloramines at our wells to treat the fresh water. Unfortunately, this aquifer has been impacted by saltwater intrusion. It still accounts for about 18 percent of our water supply.

As saltwater intrusion impacts the remainder of the fresh water source, the island will face additional need for an alternative water supply. This is likely to come from further development of our groundwater resources that can be treated using reverse osmosis or a similar membrane-based process.