Groundwater Resource and Mining Study

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Groundwater Resource and Mining Study

• Lee County CN-03-16
• Presentation to Lee Board of County Commissioners
• Management Planning
• June 6, 2005

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Geologic Data Base/Viewlog

• Integrated WRS Database with USGS Wells
• Generated Refined Surfaces for Lee County Area
• Frame Work for Groundwater Flow Modeling
• Aquifer Parameter Refinement
• Re-grided to Lee County Model Area

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Well Lithology Data Points
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Geologic and Hydrogeologic Units
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Geologic Section Locations
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Aquifers

• Floridan
• Intermediate
• Surficial

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Log Hydraulic Conductivity (ft/day) of the Ochopee
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Water Level Data Base/Viewlog

• Compiled Water Level Data Base going back to
  early 1970s
• Water Levels primarily from USGS and Lee County
  (Utilities and NRM)
• Over 285,000 Data Points in Data Base from 550
  Wells
• Aquifers included in Database are Surficial
  (Holocene-Pliocene), Tamiami, Sandstone,
  Mid-Hawthorn and Lower Hawthorn Cross Referenced
  to Lithologic Units

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Water Levels Data Points
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Kriged Median May 96 - 03 Water Levels in
Holocene/Pliocene
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Kriged Median September 96 - 03 Water Levels in
Holocene/Pliocene
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Location of USGS Wells in the Vicinity of the
City of Fort Myers Wellfields
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Impact of DRGR Land Use on Water Levels

• Temporal Aerial Change in Water Levels
• Reviewed Rainfall Data from Late 80s to 03 for
  Similar Antecedent Rainfall Conditions
• Selected May 89 to 92 May 00 to 03
• Selected October 89 to 92 October 00 to 03
• Antecedent Rainfall Conditions Important to
  Surficial System
• Averaged Water Levels for each WL Well for the
  Four Periods and Generated Kriged Surfaces
• Calculated the Difference between the Two Wet
  Two Dry Season Periods

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Average Surficial Elevation from May of 89, 90,
91 92
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Average Surficial Elevation from May of 00, 01,
02 03
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Difference in Surficial for May (end of dry
season)
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Difference in Surficial for October (end of wet
season)
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Difference in Tamiami for May (end of dry season)
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Difference in Tamiami for October (end of wet
season)
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Difference in Sandstone for May (end of dry
season)
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Difference in Sandstone for October (end of wet
season)
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Difference in Mid-Hawthorn for May (end of dry
season)
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Difference in Mid-Hawthorn for October (end of
wet season)
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Modflow Groundwater Flow Model

• Three Dimensional Groundwater Flow
• Rainfall Recharge
• Recharge from Surface Water
• Drainage Features
• Tidal Surface Water Bodies
• Evapotranspiration
• Land Cover
• Well Pumpage
• Aquifer Storage Recovery

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Hydrologic Cycle
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Geologic and Hydrogeologic Units
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Topography
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Groundwater Flow Model Domain (478 rows x 563
columns)
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Average Annual Lee County Precipitation in Inches
(1996-2003)
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Average Wet Period (June through October) Lee
County Precipitation Rate in Inches/Year
(1996-2003)
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Average Dry Period (November through May) Lee
County Precipitation Rate in Inches/Year
(1996-2003)
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Land Cover
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Lee Co Utilities Service Area
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LCU Wellfields

• Green Meadows Wellfield
• groundwater from the Surficial and Sandstone
  aquifers
• Corkscrew Wellfield
• groundwater from the Surficial and Sandstone
  aquifers
• expansion under way in Lower Hawthorn and Aquifer
  Storage and Recovery (ASR) in Mid-Hawthorn

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LCU Wellfields (continued)

• Waterway Estates
• groundwater drawn from the Sandstone,
  Mid-Hawthorne and Surficial aquifers
• San Carlos
• groundwater from Surficial aquifer
• Pinewoods
• groundwater from Surficial and Sandstone aquifers
  
• College Parkway
• groundwater from the Mid-Hawthorn aquifer
• New North Lee Co Wellfield
• groundwater from Lower Hawthorn

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Other Wellfields Included in Groundwater Model

• Florida Water Services plant in Lehigh
• - groundwater from Sandstone aquifer
• Bonita Springs Utilities
• - groundwater from Surficial aquifer
• City of Cape Coral
• - groundwater from Surficial aquifer

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Steady State Groundwater Flow Model Calibration

• Model Calibrated to Median Monthly Water Level
  Data for 1996 to 2003
• Simulated vs. Observed Data Excellent Calibration
  Achieved
• Important to Identify Recharge Areas and Rates
• Important to First Calibrate to Steady State
  before Transient Calibration

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Observed vs. Simulated Steady State Holocene
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Observed vs. Simulated Steady State Ochopee
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Transient Groundwater Flow Model Calibration

• Carried Calibrated Steady State Model into
  Transient Wet and Dry Starting in 1998 thru 2001
• Excellent Simulated vs. Observed Heads all
  Aquifers

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Observed vs. Simulated Transient Calibration Plot
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Observed vs. Simulated Transient Calibration Plot
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Dry Season Steady State Holocene (96 03)
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Wet Season Steady State Holocene (96 03)
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Average Annual Steady State Holocene
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Average Annual Steady State Ochopee
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Average Annual Steady State Sandstone
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Steady Average Annual State Mid-Hawthorn
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Projected 2025 Pumpage by Wellfield
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GROUNDWATER RECHARGE DETERMINATION

• Net Recharge to Water Table Evaluation Using
  Steady State Simulations
• Highly Dependent upon Land Uses
• Induced Recharge from Groundwater Withdrawals and
  Drainage

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Net Recharge to Water Table Steady State Dry
Season
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Net Recharge to Water Table Steady State Dry
Season
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Net Recharge to Water Table Steady State Wet
Season
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Net Recharge to Water Table Steady State Wet
Season
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Net Recharge to Water Table Steady State Wet
Season
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Net Recharge to Water Table SS Wet Season
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Net Recharge to Water Table Steady State Wet
Season
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Net Recharge to Water Table Steady State Wet
Season
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Steady State (Average) Net Recharge by Land Cover
(inches per year)
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Wet Season Net Recharge by Landcover (inches per
year)
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Dry Season Net Recharge by Landcover (inches per
year)
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Lower and Upper Caloosahatchee Tidal Budget
Regions
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Groundwater Flow to Tide (MGD)
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Simulated Holocene Drainage Drawdown Impact in
(ft) for Selected Canals

• Steady state
• Assume equivalent Land Cover

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Simulated Ochopee Drainage Drawdown Impact in
(ft) for Selected Canals

• Steady state
• Assume equivalent land cover

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Groundwater Conclusions

• Geologic and water level databases are the most
  comprehensive evaluation of the groundwater
  resources of Lee County that have been completed
  to date
• Net recharge to the water table is affected by a
  number of factors, not the least of which is
  irrigation
• Modeling supports DRGR is an effective
  groundwater recharge area
• Recharge is the greatest in the southern DRGR

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Groundwater Recommendations

• Install additional monitor wells in Southern
  Northern DRGR as part of the existing Natural
  Resource Management Monitoring Program
• Update and maintain the water level data base on
  a regular basis so that it is available for
  future
• Further evaluation of the role that anthropogenic
  (man made) drainage features play on the
  hydrologic system is warranted
• High quality lithologic boring logs should be
  collected from geotechnical and hydrogeologic
  testing activities

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2002 Mining Inventory
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Local Governance of Water/ Mining Resources

• Lee Plan
• DRGR
• Wellfield Protection
• Zoning
• Mining
• Smart Growth
• Lee Mitigation Plan

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2002 Existing Mine Inventory
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Mines Included in Model and Inventory
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Existing Mine Inventory

• 2002 Inventory of Mine Pits from Aerial Photo
  5,544 acres
• Sum does not include development SWM Ponds/Lakes
• 329 Polygons Inventoried
• Excavated Overburden Estimated to be 119.3
  Million Cubic Yards
• Excavated Rock estimated to be 161.1 Million
  Cubic Yards

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Potential Future Mining Inventory
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DRGR, Open Rural Land Use Categories
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Additional Considerations

• No Future Mining Allowed in Bonita Springs City
  Limits
• Exclude Developed Areas
• Access to Property
• Some Wetlands Can Be Mitigated Away
• Properties Disregarded Due to Large Wetlands

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Lee Mitigation Map
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Inventoried Areas for Potential Future Mining
Activity (Mitigation Map Areas in blue)
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Potential Future Mine Areas
Including Mitigation Map Areas

• DRGR 29,050 acres
• Rural 10,540 acres
• Open Lands 9,036 acres

Excluding Mitigation Map Areas

• DRGR 18,809 acres
• Rural 9,754 acres
• Open Lands 4,986 acres

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Potential Future Mine Quantities of Overburden
Including Mitigation Map Areas

• DRGR 891.6 Million Cu. Yds.
• Rural 206.2 Million Cu. Yds.
• Open Lands 224 Million Cu. Yds.
• Total 1,321.8 Million Cu. Yds.

Excluding Mitigation Map Areas

• DRGR 520.3 Million Cu. Yds.
• Rural 189.9 Million Cu. Yds.
• Open Lands 91.1 Million Cu. Yds.
• Total 801.3 Million Cu. Yds.

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Potential Future Mine Quantities of Rock
Including Mitigation Map Areas

• DRGR 2,676.1 Million Cu. Yds.
• Rural 242.5 Million Cu. Yds.
• Open Lands 150.9 Million Cu. Yds.
• Total 3,069.5 Million Cu. Yds.

Excluding Mitigation Map Areas

• DRGR 1,800.9 Million Cu. Yds.
• Rural 209.1 Million Cu. Yds.
• Open Lands 80.2 Million Cu. Yds.
• Total 2,090.2 Million Cu. Yds.

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Demand Projections for Materials
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Lee County Mining Facts (source Florida Limerock
Aggregate Institute)

• There is no state or national requirement for a
  quarry producer to report volumes produced or
  sold
• In Florida each person requires over 9 tons of
  stone and sand per year of which 7.2 tons is
  crushed stone and manufactured sand
• Lee County is the second largest proven stone
  reserve location in Florida behind the Lake Belt
  area in Miami-Dade County

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Lee County Mining Facts (source Florida Limerock
Aggregate Institute)

• Lee County would currently rank second in annual
  production for direct use by citizens of Florida
• Should crushed stone and manufactured sand have
  to come from another location most likely the
  Lake Belt or the Tampa Port the added cost per
  ton would be approximately 12.00

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Wet Season Steady State Holocene (96 03)
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Considerations for Design

• Pre-mining vs. Post Mining

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Mining Conclusions

• Mining has both positive and negative impacts on
  the groundwater resources in Lee County
• Estimated reserves indicate that Lee County has
  more than sufficient reserves to meet the demand
  generated by development well into the future
• A significant quantity of material mined in Lee
  County is being exported to adjacent counties
• Total annual sales of commercially mined
  materials in Lee County is in excess of
  80,000,000

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Mining Recommendations

• Implement annual reporting for mines that
  specifically details the areas being mined, the
  quantity and type of material being extracted,
  depths of excavations, aerial photographs, and
  estimated reserves
• Encourage mining plans be designed so as to
  minimize the adverse long-term impacts
• Case by case determination of mine depths and
  setbacks based upon location

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Mining Recommendations

• Mines to be designed to maximize their recharge
  potential
• Regulate land uses surrounding mining borrow pits
  that potentially could degrade the surface water
  and groundwater
• Evaluate borrow pits impact on the wellfield
  protection ordinance
• Segment mine pits to prevent adverse up-gradient
  drainage impacts

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Flowways Mapping