HILTON HEAD WATER SUPPLY & SALTWATER INTRUSION. Beaufort County Council September 2012

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1 HILTON HEAD WATER SUPPLY & SALTWATER INTRUSION Beaufort County Council September 2012

2 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 2

3 HILTON HEAD PSD 18,000 customers 4 water sources o Reverse Osmosis - Middle Floridan Aquifer o Wholesale surface water o Upper Floridan Aquifer o Reused water Aquifer Storage & Recovery (ASR) well Peak demand of 11 million gallons 3

4 BROAD CREEK PSD 5,000 customers 3 water sources o Upper Floridan Aquifer o Wholesale surface water o Reused water Peak demand of 4 million gallons 4

5 SOUTH ISLAND PSD 25,000 customers 3 water sources o Upper Floridan Aquifer o Reverse Osmosis - Cretaceous Aquifer o Reused water 2 Aquifer Storage & Recovery (ASR) wells (under construction) Peak demand of 8.5 million gallons 5

6 ISLAND PSDS REUSED WATER Hilton Head Island = 100% Reused Water o Golf course irrigation o Wetlands nourishment Together, we recycle over 2.5 billion gal./year! 6

7 SALTWATER INTRUSION 7

8 Feet Below Mean Sea Level 0 Aquifers and Confining Layers in the Hilton Head Island Area Surficial Aquifer Sand and Clay 100 Hawthorn Confining Layer Clay 200 Upper Floridan Aquifer Permeable Limestone (under Capacity Use Area restrictions) Middle Semi Confining Unit Less Permeable Limestone Middle Floridan Aquifer Permeable Limestone 8

9 UPPER FLORIDAN AQUIFER One of the largest aquifers in the world o Coastal Carolinas to the Florida Everglades Our original source of water Inexpensive Little treatment required Upper Floridan Aquifer well house 9

10 Pre-pumping Equipotential Map of the Upper Floridan Aquifer in South Carolina 10

11 Cone of Depression in the Upper Floridan Aquifer Associated with Withdrawals at Savannah Adapted from Smith,

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13 SALTWATER INTRUSION USGS Conceptual Model 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 13

14 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 14

15 A LONG-TERM PROBLEM 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 15

16 THE ISLAND S RESPONSE Reduced pumping by more than 40% Reused water Efficiency/conservation customer education Islandwide irrigation ordinance Capital projects to replace lost supply 16

17 HILTON HEAD PSD UPPER FLORIDAN WELLS 6 lost to saltwater intrusion since of remaining 6 slated to be lost by

18 SALTWATER INTRUSION TIMELINE (1995) S.C. DHEC declares capacity use zone (1999) Pipeline provides surface water from mainland (2000) PSD begins losing wells ( ) Feasibility studies (2009) Opened RO Plant (2011) Built ASR Well 18

19 SOUTH ISLAND PSD Recently discovered high chloride levels in the Long Cove Potable Well #1 have resulted in the well being removed from service. 19

20 FINANCIAL IMPACT ON HILTON HEAD RATE/TAXPAYERS 20

21 SALTWATER INTRUSION COSTS Since 1998 $77 million spent by Hilton Head PSD fighting saltwater intrusion o Capital o Operations o Debt Service o Purchased Water ($16.7 million) $20 million spent by Broad Creek PSD $32 million spent by South Island PSD o Supplemental water supply Reverse Osmosis plant o 2 Aquifer Storage & Recovery wells under construction $129 million spent by Hilton Head, South Island, and Broad Creek PSDs combined 21

22 SALTWATER INTRUSION COSTS In the next 20 years $50 million potential to be spent by Hilton Head PSD o Capital o Operations o Debt Service o 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 22

23 GOING IT ALONE No state or federal funds have been used to cover these saltwater-intrusion related costs Solely borne by Hilton Head Island rate/taxpayers 23

24 CAPITAL PROJECTS NEEDED TO REPLACE LOST SUPPLY 24

25 HILTON HEAD PSD RO PLANT 3 MGD 6 MGD potential Middle Floridan Aquifer, brackish 3 raw water wells, 600 ft. deep 25

26 WHAT IS AQUIFER STORAGE & RECOVERY? 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 26

27 Aquifer Storage & Recovery Well Confining Layer Confining Layer Native Groundwater Buffer Zone Stored Water Stored Water Buffer Zone Native Groundwater Confining Layer 27

28 HILTON HEAD PSD AQUIFER STORAGE & RECOVERY WELL Built in Fall 2011 $2.5 million 2 MGD in summer 218 MG bubble 28

29 ADDITIONAL INFRASTRUCTURE NEEDED Larger mains needed to distribute new sources of water throughout island 16-inch transmission main into Hilton Head Plantation 29

30 ADDITIONAL INFRASTRUCTURE NEEDED Booster station at Wild Horse Tower 30

31 THE FUTURE 31

32 FUTURE WATER SUPPLY OPTIONS HILTON HEAD PSD Efficiency PSD rain garden demonstration at Coastal Discovery Museum Expanded reused water Brackish Reverse Osmosis o Middle Floridan o Lower Floridan o Cretaceous Wholesale surface water Aquifer Storage & Recovery 32

33 FUTURE WATER SUPPLY OPTIONS BROAD CREEK PSD Additional wholesale surface water capacity Use of Aquifer Storage & Recovery Additional upgrades of pipeline infrastructure 33

34 FUTURE WATER SUPPLY OPTIONS SOUTH ISLAND PSD Infrastructure Planning for Years Out Aquifer Storage & Recovery Reverse Osmosis treatment Distribution system upgrades Sea Pines Montessori School rain garden demonstration project 34

35 FUTURE WATER SUPPLY OPTIONS SOUTH ISLAND PSD Short and Long Term Projections 5-year projection: o 2 ASR Wells Long-term projection: o Total of 5 ASR wells o 1 Reverse Osmosis plant 35

36 Questions? 36