Nutana Slope Failure_media Presentation

8/9/2019 Nutana Slope Failure_media Presentation

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2012 to Present:

20132012


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Causes of the Failure

1 GEOLOGY 2 GEOMETRY 3 GROUND WATER

Weak soil Steep slope High watertable due toincreased

precipitation


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Causes of the Failure:

SLIP PLANE

1 GEOLOGY

2 GEOMETRY

3 GROUND WATER

GROUND WATER LEVEL

11 th StCherryLane

SaskCres


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10 Year Average Rainfall - Saskatoon


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Groundwater Levels - Saskatoon


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Status of Slope

MovementPossible

Not stable

Continued movement toward Sask Cres


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Remediation Options

Conceptual only

Target: 50% MORE stabilizing force

4 general options evaluatedNo 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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Option 2

Address

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

Doesnt meet stability target (only 20%)

3 GROUND WATER


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GROUND WATER LEVELSLIP 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

FORCESPULLING

SLOPEDOWN

FORCESHOLDING

SLOPEUP
http://www.google.ca/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&docid=2pxxozlrKYa60M&tbnid=zPfZoKegHV6uqM:&ved=0CAUQjRw&url=http://www.clipartbest.com/check-mark-symbol&ei=t8dxU9aPK4e58wGniIDACg&bvm=bv.66330100,d.aWw&psig=AFQjCNGCGu8VsRLtTbAigasU0OAIivJrIQ&ust=1400052016654975http://www.google.ca/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&docid=2pxxozlrKYa60M&tbnid=zPfZoKegHV6uqM:&ved=0CAUQjRw&url=http://www.clipartbest.com/check-mark-symbol&ei=t8dxU9aPK4e58wGniIDACg&bvm=bv.66330100,d.aWw&psig=AFQjCNGCGu8VsRLtTbAigasU0OAIivJrIQ&ust=1400052016654975


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Option 4:

Address AND

Shear zone replacement


Keeps houses in place

3 GROUND WATER 1 GEOLOGY

FORCESPULLING

SLOPEDOWN

FORCESHOLDING

SLOPEUP
http://www.google.ca/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&docid=2pxxozlrKYa60M&tbnid=zPfZoKegHV6uqM:&ved=0CAUQjRw&url=http://www.clipartbest.com/check-mark-symbol&ei=t8dxU9aPK4e58wGniIDACg&bvm=bv.66330100,d.aWw&psig=AFQjCNGCGu8VsRLtTbAigasU0OAIivJrIQ&ust=1400052016654975


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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


Keeps houses in place

3 GROUND WATER 1 GEOLOGY

FORCESPULLING

SLOPEDOWN

FORCESHOLDING

SLOPEUP

Option 4:
http://www.google.ca/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&docid=2pxxozlrKYa60M&tbnid=zPfZoKegHV6uqM:&ved=0CAUQjRw&url=http://www.clipartbest.com/check-mark-symbol&ei=t8dxU9aPK4e58wGniIDACg&bvm=bv.66330100,d.aWw&psig=AFQjCNGCGu8VsRLtTbAigasU0OAIivJrIQ&ust=1400052016654975http://www.google.ca/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&docid=2pxxozlrKYa60M&tbnid=zPfZoKegHV6uqM:&ved=0CAUQjRw&url=http://www.clipartbest.com/check-mark-symbol&ei=t8dxU9aPK4e58wGniIDACg&bvm=bv.66330100,d.aWw&psig=AFQjCNGCGu8VsRLtTbAigasU0OAIivJrIQ&ust=1400052016654975


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Remediation Summary:

OPTION PROS CONS ESTIMATED

COST 1) Do Nothing No cost

HIGH risk ofcontinued failure $0

2) Lower Water Table

Minimaldisturbance

Lowers wet year

risk

Does not meet targetstability $4.5M

3) Re-Grade Slope(and lower water table)

Meets stabilitytarget

Reduced long termrisk

Significant disruption Removal of structures $6.5

10M

4) Shear ZoneModification(and lower water table)

Meets stabilitytarget

Maintainsstructures

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 andcostly to resolve


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Public SafetyContinues to be primary focus of the

Continue detailed monitoring

Provide residents with everything we know

Evacuation Alert


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Nutana Slope Failure_media Presentation

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