HILTON HEAD WATER SUPPLY

&SALTWATER INTRUSION

Beaufort County Council September 2012

HILTON HEAD’S WATER UTILITIES

• Three public water, wastewater, reused water utilities on Hilton Head

• Formerly, 10 different utilities on island

• Result of private development

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HILTON HEAD PSD

• 18,000 customers

• 4 water sources o Reverse Osmosis

- Middle Floridan Aquifero Wholesale surface water o Upper Floridan Aquifer o Reused water

• Aquifer Storage & Recovery (ASR) well

• Peak demand of 11 million gallons

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BROAD CREEK PSD

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• 5,000 customers

• 3 water sourceso Upper Floridan

Aquifero Wholesale surface

watero Reused water

• Peak demand of 4 million gallons

SOUTH ISLAND PSD

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• 25,000 customers

• 3 water sourceso Upper Floridan Aquifero Reverse Osmosis

- Cretaceous Aquifero Reused water

• 2 Aquifer Storage & Recovery (ASR) wells (under construction)

• Peak demand of 8.5 million gallons

ISLAND PSDS’ REUSED WATER

• Hilton Head Island = 100% Reused Watero Golf course irrigationo Wetlands nourishment

• Together, we recycle over 2.5 billion gal./year!

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SALTWATER INTRUSION

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Aquifers and Confining Layers in the Hilton Head Island Area

Feet Below Mean Sea Level

0

100

200

300

400

500

600

Surficial Aquifer – Sand and Clay

Hawthorn Confining Layer ‐ Clay

Upper Floridan Aquifer – Permeable Limestone (under Capacity Use Area restrictions)

Middle Semi‐Confining Unit – Less Permeable Limestone

Middle Floridan Aquifer – Permeable Limestone

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UPPER FLORIDAN AQUIFER

• One of the largest aquifers in the worldo Coastal Carolinas to the Florida Everglades

• Our original source of water

• Inexpensive

• Little treatment required

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Upper Floridan Aquifer well house

Pre-pumping Equipotential Map of the Upper Floridan Aquifer in South Carolina

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Cone of Depression in

the Upper Floridan Aquifer

Associated with

Withdrawals at Savannah

Adapted from Smith, 1998

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• Caused by overpumping in Savannah region

• Nothing the island can do to stop saltwater intrusion

• Saltwater intrusion is accelerating – 400 ft. or more a year

• Ultimately, all Upper Floridan Wells on Hilton Head will be lost to the intrusion

SALTWATER INTRUSION

USGS Conceptual Model

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SALTWATER INTRUSION

• A regional issue (GA/SC)

• More than $20 million spent on studies/models alone

• Joint stakeholder committee between the two states

Result?

• The Upper Floridan is being mined!

• Without curtailment, this natural resource will be destroyed forever

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A LONG-TERM PROBLEM

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• GA/SC will need to cut withdrawals by 80%

• Studies show all Upper Floridan wells on Hilton Head will eventually be impacted by saltwater intrusion

• Saltwater intrusion is forever – more than 300 years to recede

THE ISLAND’S RESPONSE

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• Reduced pumping by more than 40%

• Reused water

• Efficiency/conservation customer education

• Islandwide irrigation ordinance

• Capital projects to replace lost supply

HILTON HEAD PSD UPPER FLORIDAN

WELLS

• 6 lost to saltwater intrusion since 2000

• 5 of remaining 6 slated to be lost by 2024

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SALTWATER INTRUSION TIMELINE

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• (1995) S.C. DHEC declares capacity use zone

• (1999) Pipeline provides surface water from mainland

• (2000) PSD begins losing wells

• (2004-2006) Feasibility studies

• (2009) Opened RO Plant

• (2011) Built ASR Well

SOUTH ISLAND PSD

• Recently discovered high chloride levels in the Long Cove Potable Well #1 have resulted in the well being removed from service.

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FINANCIAL IMPACT ON HILTON HEAD RATE/TAXPAYERS

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SALTWATER INTRUSION COSTS

• $77 million spent by Hilton Head PSD fighting saltwater intrusion

o Capitalo Operationso Debt Serviceo Purchased Water ($16.7 million)

• $20 million spent by Broad Creek PSD

• $32 million spent by South Island PSDo Supplemental water supply – Reverse Osmosis planto 2 Aquifer Storage & Recovery wells under

construction

• $129 million spent by Hilton Head, South Island, and Broad Creek PSDs combined

Since 1998…

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SALTWATER INTRUSION COSTS

In the next 20 years …

• $50 million potential to be spent by Hilton Head PSD

o Capitalo Operationso Debt Serviceo Purchased Water

• $25 million projected capital costs for South Island PSD through 2025

• $5 million potential to be spent by Broad Creek PSD

• $80 million potential to be spent by Hilton Head, South Island, and Broad Creek PSDs combined

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GOING IT ALONE

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• No state or federal funds have been used to cover these saltwater-intrusion related costs

• Solely borne by Hilton Head Island rate/taxpayers

CAPITAL PROJECTS NEEDED TO REPLACE

LOST SUPPLY

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HILTON HEAD PSD RO PLANT

• 3 MGD

• 6 MGD potential

• Middle Floridan Aquifer, brackish

• 3 raw water wells, 600 ft. deep

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WHAT IS AQUIFER STORAGE & RECOVERY?

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• Store treated water in the underground aquifer during times of low demand

• Withdraw and retreat during times of high or peak demand

• A water storage technique; not a new source of water

Aquifer Storage & Recovery Well

Confining Layer Confining Layer

NativeGroundwater

BufferZone Stored

WaterStored Water

Buffer Zone

Native Groundwater

Confining Layer 27

• Built in Fall 2011• $2.5 million• 2 MGD in summer• 218 MG bubble

HILTON HEAD PSDAQUIFER STORAGE & RECOVERY WELL

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ADDITIONAL INFRASTRUCTURE NEEDED

16-inch transmission main into Hilton Head Plantation

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Larger mains needed to distribute new sources of water throughout island

ADDITIONAL INFRASTRUCTURE NEEDED

• Booster station at Wild Horse Tower

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THE FUTURE

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FUTURE WATER SUPPLY OPTIONSHILTON HEAD PSD

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• Efficiency

• Expanded reused water

• Brackish Reverse Osmosiso Middle Floridano Lower Floridano Cretaceous

• Wholesale surface water

• Aquifer Storage & Recovery

PSD rain garden demonstration at Coastal Discovery Museum

FUTURE WATER SUPPLY OPTIONSBROAD CREEK PSD

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• Additional wholesale surface water capacity

• Use of Aquifer Storage & Recovery

• Additional upgrades of pipeline infrastructure

FUTURE WATER SUPPLY OPTIONSSOUTH ISLAND PSD

• Aquifer Storage & Recovery

• Reverse Osmosis treatment

• Distribution system upgrades

Infrastructure Planning for 20 – 25 Years Out

Sea Pines Montessori School rain garden demonstration project34

FUTURE WATER SUPPLY OPTIONSSOUTH ISLAND PSD

• 5-year projection:o 2 ASR Wells

• Long-term projection:o Total of 5 ASR wellso 1 Reverse Osmosis plant

Short and Long Term Projections

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Questions?

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