April 15, 2004

1
Recent ASR Developments in Southwest Florida
Presented at the American Ground Water Trust
Aquifer Storage Recovery IV Tampa, Florida
Presented by Mark McNeal, PG /CH2M HILL
April 15, 2004
2
Three primary types of ASR projects are in
operation in Southwest Florida

• Potable Water ASR
• Reclaimed Water ASR
• Partially Treated Surface Water ASR

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ASR Projects in Southwest Florida
Potable Water ASR Project
Reclaimed Water ASR Project
Partially Treated Surface Water ASR Project
4
Select Southwest Florida Potable Water ASR
Projects

• Peace River/Manasota Regional Water Supply
  Authority
• Manatee County
• City of Tampa
• City of Bradenton
• City of Fort Myers
• City of Punta Gorda
• Bonita Springs Utilities

Bonita Springs Utilities
5
Manatee County had the first ASR wells to come on
line in Florida

• Two ASR wells completed in 1983 at Lake Manatee
• Stores treated surface water from the Manatee
  River
• Storage zone is relatively fresh, at upper limits
  of drinking water

• Recently expanded to 6 wells
• Approximately 10 mgd ASR capacity
• Demonstrates success of ASR in this area

6
The Peace River Facility relies on its ASR system
to meet its dry weather demands
7
The Peace River system is another ASR success
story in SW Florida

• Largest ASR system in eastern US
• Additional expansion underway - up to 26
  additional ASR wells

PRMRWSA Boundary
S-1
S-2
WF1
T-1
AP-1
SR761
S-5R
S-3R
S-6
S-9R
Reservoir
S-7
S-8
Peace River
Railroad
WF2
Kings Highway (SR769)
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The older ASR wells were evaluated as the initial
step of the ASR expansion

• 16 years of operational data were reviewed to
  determine effectiveness of ASR WF 1
• 2.5 BG of water was stored at the site, and 2 BG
  was recovered over a 2-year period

9
Storage zone selection is becoming an important
decision for many ASR facilities

• Many utilities are faced with a decision -
  expand outward or utilize multiple zones
• Competing users or impacts to sensitive surface
  water bodies must be addressed
• Recovery efficiencies will likely decrease as
  deeper, more brackish zones are utilized
• Certain zones may be more apt to experience
  geochemical changes than others
• Stacking wells may help control upconing

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0 200 400 600 800 1000 1200 1400 1600
The Suwannee Zone is the primary storage interval
at the site
TDS (mg/L)
Geologic Unit
Hawthorn Group
1 mgd
1 mgd
Tampa Zone
500
3 mgd
900
Suwannee Zone
Depth in Feet
Ocala Limestone
Avon Park Formation
2900
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Six alternatives are being considered for 38 mgd
firm capacity

• Existing WUP scenario is a dispersed WF in the
  Suwannee Zone
• 5 other scenarios consider various spacings,
  locations, and storage intervals

12
Cost estimates were prepared for each of the
26-well ASR expansion scenarios

• The existing WUP layout was the most expensive
  alternative at 17.3M
• The other five scenarios ranged from 13.1M to
  14.9M

• Construction costs equate to about 0.50 to 0.70
  per mgd of ASR capacity
• Assuming 100 MG storage per well, 5k to 7k /MG
  stored

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Care must be taken that future expansions do not
impact existing ASR well performance
14
Tampas ASR system is important to west-central
Florida

• Water resources are stressed in this area

• Alternative water supplies under development
• A successful ASR system would provide benefits
  not only to the City, but to the region as well

• Tampa has constructed its initial system
• 8-well, 10 mgd system
• Constructed in an urban setting
• Tampa is exploring ASR expansion options in the
  Avon Park Fm

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The City of Tampa has faced several challenges
with their ASR program

• Geology is leakier in this area relative to the
  successful ASR systems to the south
• Upconing of saline water from below occurs during
  recovery
• Other geochemical changes have also been observed
• Returning water to the WTP has allowed aggressive
  recovery

ASR-1
Cycle 3
Cycle 2
Cycle 1
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Water Use Permitting has also been challenging
for Tampa

• Numerous domestic well owners (none have been
  impacted)
• Potential for sinkholes in an urban area (none)
• Lake level responses
• Urban wetlands?
• Withdrawal schedule to allow recharge
• How to bank water during wet years to recover
  during dry yrs
• Rolling avg not allowed
• Fluctuating chloride concentrations in ASR wells
  and MWs

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Chloride concentrations show temporary response
during recovery

• Chloride in nearby storage zone MWs increases
  from 20 to as high as 850 mg/L

• Once recharge begins, storage zone freshens
• No noticeable impact to shallow (domestic) zone -
  no impacts to adjacent users

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Tampa has also has had many successes...

• Able to co-exist with residents
• No impacts to private well owners
• No sinkholes linked to ASR pumpage
• No ASR-related impacts to neighborhood
• Lake level responses not typical ofgroundwater
  production in this area
• Surficial water level impacts insignificant
• attributed to deeper well casing settingsand
  cyclical nature of ASR operations
• Able to provide about 15 percent of the Citys
  water supply during the 2000-2002 drought
• CO2 treatment to increase ASR well capacity

19
Tampas carbon dioxide treatment has effectively
replaced well acidization

• Initial investment of about 1,000 for CO2
  equipment
• Now costs about 100 per CO2 event vs. 25k-30k
  for acidization

• No by-products requiring disposal
• No chloride increase _at_ ASR wells
• No pump removal
• No kidding
• Increased injectivity from less than 1 to 40
  gpm/psi
• 10 MG recharged in 1 week vs. 3 months

2nd CO2 application
Post-CO2
Pre-CO2
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Status of Southwest Florida reclaimed water ASR
projects

• Operational testing has been initiated
• Englewood Water District Hillsborough Co.
• Constructed and ready to start testing
• St. Petersburg Manatee County
• Others permitted to construct systems
• City of Sarasota, Lehigh Acres
• In the feasibility study/permitting phase
• Sarasota Co., Pinellas Co., Clearwater, Largo,
  and others

21
Englewoods reclaimed water ASR system is
undergoing testing

• Permit issued in 1999 - renewal underway
• System constructed at WWTP in 2000
• Storage zone 500 to 700 feet bls
• Storage zone was saline (20,000 mg/L TDS)
• Began operational testing in July 2001
• Required a WQCE for color - other drinking water
  standards were met
• Initial cycle testing has been limited but is
  encouraging

22
Cycle testing has posed challenges for EWD

• The WWTP was a zero discharge facility, with
  reuse accounting for all discharges
• EWD is sewering the area, with flows increasing
  significantly
• Additional reuse customers have been brought
  online within the past year
• EWD has 500 MG in storage, as reuse demand has
  not kept up with supply

• Timing can be challenging for reclaimed water ASR
• Cant add reuse customers without ASR
• Cant test w/o sufficient reuse demand
• Result A deep injection well was constructed
• Will allow EWD to perform more aggressive cycle
  testing
• Some water will be wasted to confirm well
  performance

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The City of St. Petersburgs ASR program is unique

• Located at its Southwest WRF
• Couples ASR with DIW system
• Freshening in overlying zones
• Storage zone previously 30,000 mg/L TDS, now
  5,000 mg/L TDS
• Solute transport modeling suggests this will
  improve early recovery efficiency from 3 to an
  estimated 35
• Recovery endpoint expected to be 1500-2000 mg/L
  TDS
• Testing expected to begin soon

St. Petersburg ASR site
Solute Transport Model Output
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Summary

• ASR systems are alive and well in Southwest FL
• ASR allows effective use of our major rivers
• Approximately 40 mgd capacity among top 3 potable
  water ASR systems in southwest FL, with several
  other smaller ASR systems as well
• Reclaimed water ASR projects are advancing due to
  the importance of reuse in the area and the
  seasonal variations between supply and demand
• Only one partially treated surface water ASR site
  is in operation, but others are anticipated in
  the future
• Although each program has its challenges, ASR
  remains a very cost effective, safe alternative
  water supply option with significant importance
  to SW FL