2012 to Present: 2013 2012 Causes of the Failure 3 GROUND WATER - - PowerPoint PPT Presentation

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2012 to Present: 2013 2012 Causes of the Failure 3 GROUND WATER - - PowerPoint PPT Presentation

Jul 06, 2023 99 likes •377 views

2012 to Present: 2013 2012 Causes of the Failure 3 GROUND WATER 1 GEOLOGY 2 GEOMETRY Weak soil Steep slope High water table due to increased precipitation 1 GEOLOGY Causes of the Failure: 2 GEOMETRY 11 th St 3 GROUND WATER

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SLIDE 1
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2012 to Present:

2013 2012

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Causes of the Failure

1 GEOLOGY 2 GEOMETRY 3 GROUND WATER

Weak soil Steep slope High water table due to increased precipitation

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SLIDE 4
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Causes of the Failure:

SLIP PLANE

1 GEOLOGY 2 GEOMETRY 3 GROUND WATER

GROUND WATER LEVEL

11th St Cherry Lane Sask Cres

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10 Year Average Rainfall - Saskatoon

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Groundwater Levels - Saskatoon

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Status of Slope

Movement Possible

  • Not stable
  • Continued movement toward Sask Cres
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Remediation Options

  • Conceptual only
  • Target: 50% MORE stabilizing force
  • 4 general options evaluated

No Movement

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Option 1

  • Do Nothing
  • Continued movement
  • Risk increases as groundwater increases
  • Slide area will expand in time
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SLIDE 11

Option 2

  • Address
  • Install dewatering trenches (11th St & Cherry Lane)

3

GROUND WATER

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SLIP PLANE GROUND WATER LEVEL GROUND WATER LEVEL

Option 2

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Option 2

  • Address
  • Install dewatering trenches (11th St & Cherry Lane)
  • Doesn’t meet stability target (only 20%)

3

GROUND WATER

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Option 3:

  • Address AND
  • Flatten the slope
  • Meets 50% stability target

3 GROUND WATER 2 GEOMETRY

FORCES PULLING SLOPE DOWN FORCES HOLDING SLOPE UP

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GROUND WATER LEVEL SLIP PLANE

Option 3:

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Possible Remediation OPTION 3 Affected area

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Option 3:

  • Address AND
  • Flatten the slope
  • Meets 50% stability target
  • Significant disruption to private lots

3 GROUND WATER 2 GEOMETRY

FORCES PULLING SLOPE DOWN FORCES HOLDING SLOPE UP

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Option 4:

  • Address AND
  • “Shear zone replacement”
  • Meets 50% stability target
  • Keeps houses in place

3 GROUND WATER 1 GEOLOGY

FORCES PULLING SLOPE DOWN FORCES HOLDING SLOPE UP

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Option 4:

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Possible Remediation OPTION 4 Affected area

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Possible Remediation OPTION 4:

  • Address AND
  • “Shear zone modification”
  • Meets 50% stability target
  • Keeps houses in place

3 GROUND WATER 1 GEOLOGY

FORCES PULLING SLOPE DOWN FORCES HOLDING SLOPE UP

Option 4:

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Remediation Summary:

OPTION PROS CONS ESTIMATED COST

1) Do Nothing

  • No cost
  • HIGH risk of

continued failure

$0 2) Lower Water Table

  • Minimal

disturbance

  • Lowers “wet year”

risk

  • Does not meet target

stability

$4.5M 3) Re-Grade Slope

(and lower water table)

  • Meets stability

target

  • Reduced long term

risk

  • Significant disruption
  • Removal of structures

$6.5 – 10M 4) Shear Zone Modification

(and lower water table)

  • Meets stability

target

  • Maintains

structures

  • Difficult to construct
  • Costly

$10 – 20M

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Independent Review:

Clifton Associates

  • Independent analysis of the data
  • Purpose: To confirm remediation options
  • Conclusions:
  • Agree on methodology
  • Differing interpretation of data  even less stable
  • Remediation options feasible but may be even more costly

Verified  the problem is large and costly to resolve

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Public Safety

Continues to be primary focus of the

  • Continue detailed monitoring
  • Provide residents with everything we know
  • Evacuation Alert
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