Interim Results Regarding Additional Investigation of 25,000 AFY - - PowerPoint PPT Presentation

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Interim Results Regarding Additional Investigation of 25,000 AFY - - PowerPoint PPT Presentation

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Interim Results Regarding Additional Investigation of 25,000 AFY ALCOA Permit Presented to: Post Oak Savannah Public Hearing Milano Civic Center 120 West Avenue E Milano, TX 76556 Presented by: Steven C. Young Ph.D., PE, PG INTERA Inc.,

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SLIDE 1

Interim Results Regarding Additional Investigation of 25,000 AFY ALCOA Permit

Presented to: Post Oak Savannah Public Hearing Milano Civic Center 120 West Avenue E Milano, TX 76556 Presented by: Steven C. Young Ph.D., PE, PG INTERA Inc., November 13, 2012

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SLIDE 2

Outline

  • Review September 11 Presentation

– POSGCD Hydrogeology and Groundwater model – GMA 12 and District Management Goals – Estimated Impacts Based on Fully Implementation of Pumping

  • Interim Findings From Additional Investigation of ALCOA

Impacts

– Regional GMA 12 Desired Future Conditions – District Threshold Targets in Shallow Aquifer Zones – Change in Water Columns for Milam Wells in Carrizo-Wilcox

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SLIDE 3

Highlights of September 11 Presentation

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SLIDE 4

Carrizo-Wilcox Vertical Structure Perpendicular to Coastline

Aquifer Outcrops Where it meets Ground Surface Geologic Column

Older Formations With Increasing Depth

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SLIDE 5

Model Grid for Central QCSP and C-W GAMs

Note: From Carrizo-Wilcox GAM Stakeholder Advisory Forum Meeting ( August , 2002)

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SLIDE 6

QCSP GAM Run For GMA 12 Desired Future Conditions

Groundwater Conservation District or County Average Drawdown (ft) in Each Aquifer Calculated from the Start of Year 2000 to the Start of Year 2060 SPARTA QUEEN CITY CARRIZO CALVERT BLUFF SIMSBORO HOOPER BRAZOS VALLEY 14 12 48 109 271 177 FAYETTE COUNTY 59 58 59 126 220 172 LOST PINES 4 13 47 94 236 133 MID-EAST TEXAS

  • 3

53 67 114 96 POST OAK SAVANNAH 28 28 61 137 298 178 FALLS COUNTY

  • 1

20 LIMESTONE COUNTY

  • 9

43 40 NAVARRO COUNTY

  • 1

1 1 WILLIAMSON COUNTY

  • 11

47 56

Table B-2. Calculated Average Drawdowns Based from a Predicted Simulation Using the Central Queen City and Sparta GAM and Pumping File Run GAM_7B

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SLIDE 7

Drawdown DFCs and Thresholds from 2000 to 2060 (from Management Plan)

Aquifer Average Drawdown (ft) from 2000 to 2060 DFC for entire area Threshold for Shallow Management Area Calvert Bluff 140 20 Simsboro 300 20 Hooper 180 20

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SLIDE 8

ALCOA Permit Application

  • Historical Permit of 15,000 acre-feet per year (AFY)

(~9,300 gpm)

– Simsboro Aquifer – From 1988 to 2010, average pumping is 12,000 AFY – From 1994 to 2006, average pumping is ~30,000 AFY

  • Operating Permit for additional 25,000 AFY

(~15,500 gpm)

– 24,552.7 contiguous acres (entitled to 49,105 AFY) – 24 new wells & 32 wells with historic permit

  • Aquifer Impact Study

– Used a GAM 12 Run 7-B modified with ALCOA pumping estimates – Simulated drawdown in Simsboro from 2005 to 2040

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SLIDE 9

Predicted Average Drawdowns in Simsboro From 1980 and 2005

12 Run

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SLIDE 10

Predicted Average Drawdowns in Simsboro Management Zones from 2005

12 Run

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SLIDE 11

Example Calculation of Water Column in Wells

Example Calculations Well ID Max Water Column (ft) Min Water Column (ft) Water Column Decline (ft) % Water Column Decline Well 1 100 80 20 20% Well 2 100 60 40 40%

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SLIDE 12

Estimate Water Column Decline in Wells from 2005 to 2040 in Calvert Bluff

Percentage Change Median Values Well Count Max Water Column (ft) (2005) Min Water Column (ft) (2040) Water Column Decline (ft) < 20 % 314 412 376 33 20% - 30% 33 311 238 71 30% - 40% 15 146 90 53 40% - 60% 6 81 38 43 60% - 80% 2 66 25 40

314 33 15 6 2 50 100 150 200 250 300 350 < 20 % 20% - 30% 30% - 40% 40% - 60% 60% - 80% 80% - 100% Number of Wells in Milam County Percent Water Column Decline

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SLIDE 13

Estimate Maximum Water Column Decline in Wells from 2005 to 2040 in Simsboro

65 31 28 41 8 4 10 20 30 40 50 60 70 < 20 % 20% - 30% 30% - 40% 40% - 60% 60% - 80% 80% - 100%

Percentage Change Median Values Well Count Max Water Column (ft) (2005) Min Water Column (ft) (2040) Water Column Decline (ft) < 20 % 65 440 395 49 20% - 30% 31 264 192 69 30% - 40% 28 338 217 124 40% - 60% 41 223 104 113 60% - 80% 8 205 55 144 80% - 100% 4 48 6 39

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SLIDE 14

Estimate Maximum Water Column Decline in Wells from 2005 to 2040 in Hooper

Percentage Change Median Values Well Count Max Water Column (ft) (2005) Min Water Column (ft) (2040) Water Column Decline (ft) < 20 % 319 311 270 45 20% - 30% 67 166 131 38 30% - 40% 19 116 81 36 40% - 60% 16 74 39 35 60% - 80% 1 78 29 49

319 67 19 16 1 50 100 150 200 250 300 350 < 20 % 20% - 30% 30% - 40% 40% - 60% 60% - 80% 80% - 100% Number of Wells in Milam County Percent Water Column Decline

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SLIDE 15

Summary Points

  • Permit Meets District Rules on Well Spacings and Production

Amounts

  • Permit Provides Useful Information to Improve District

Understanding of the Simsboro

  • POSGCD has a Monitoring Network in place for the Simsboro

capable of achieving District Management goals

  • POSGCD has authority and rules in place to protect existing wells
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SLIDE 16

Interim Findings From Additional Investigation of ALCOA Impacts

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SLIDE 17

Analysis Method: Net Drawdown

  • Evaluate the Impact of a well
  • r group of wells based on

the net drawdown

  • Net drawdown is calculated

not relative to an existing water table but based on the impact of the difference between a pumping and a non-pumping scenario

Net Drawdown from 2005

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SLIDE 18

Net Drawdown in POSGCD Simsboro

20 40 60 80 100 120 140 160 180 Net Drawdown(ft) From 2005 to 2020

Simsboro in POSGCD

170 149 21 15 3 8

2020

50 100 150 200 250 300 350 400 Net Drawdown(ft) From 2005 to 2040

Simsboro in POSGCD

339 211 129 34 3 13

2040

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SLIDE 19

Contribution of Different Well Groups to Net Drawdown in POSGCD Simsboro

Well Group Simsboro 2020 Simsboro 2040 Net Drawdown (ft) 179 339 Non-POSGCD Wells 87.9% 62.1% POSGCD Wells 12.1% 37.9% ALCOA Wells 9.1% 10.0% ALCOA ( Historic ) 4.8% 3.9% Rockdale Wells 1.8% 0.9% ALCOA Wells (Permit) 4.3% 6.1%

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SLIDE 20

Net Drawdown in POSGCD Shallow Simsboro

2020 2040

10 20 30 40 50 60 Net Drawdown(ft) From 2005 to 2020

Shallow Simsboro in POSGCD

50 15 35 33 3 16

20 40 60 80 100 120 Net Drawdown(ft) From 2005 to 2040

Shallow Simsboro in POSGCD

110 33 77 64 3 28

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SLIDE 21

Contribution of Different Well Groups to Net Drawdown in POSGCD Shallow Simsboro

Well Group Shallow Simsboro 2020 Shallow Simsboro 2040 Net Drawdown(ft) 50 110 Non-POSGCD Wells 30.0% 30.0% POSGCD Wells 70.0% 70.0% ALCOA Wells 65.0% 58.6% ALCOA ( Historic ) 32.6% 25.0% Rockdale Wells 6.0% 2.7% ALCOA Wells (Permit) 32.4% 33.6%

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SLIDE 22

Status of Assessment

  • Net Drawdowns Calculated for Different Groups of Wells for Entire

and Shallow Simsboro, Hooper, and Calvert Bluff

  • Water Column Analysis is Nearly Complete

– Future impact calculations will include approximately 100 more wells – Future impact calculations will no include wells in ALCOA permitted boundary

  • Work has Not started on Impact of Changing of Well Spacing

Requirements