nutana slope failure_media presentation
TRANSCRIPT
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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
Meets 50% stability target
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
Meets 50% stability target
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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