Wabasha Street Rock Slide Assessment · 01.06.2018 · ... 2018 Wabasha Street Rock Slide Slide 1...
Transcript of Wabasha Street Rock Slide Assessment · 01.06.2018 · ... 2018 Wabasha Street Rock Slide Slide 1...
CIVIL ● MANUFACTURING ● MINING ● OIL & GAS ● POWER GENERATION
May 30, 2018 Wabasha Street Rock Slide Slide 1
CIVIL ● MANUFACTURING ● MINING ● OIL & GAS ● POWER GENERATION
Wabasha Street Rock
Slide
Slides prepared by Itasca Consulting Group May 30, 2018 Summarized for presentation by City of Saint Paul Public Works June 1, 2018
CIVIL ● MANUFACTURING ● MINING ● OIL & GAS ● POWER GENERATION
May 30, 2018 Wabasha Street Rock Slide Slide 2
• Rock slide, investigation, factual findings
Recent events
Background information (geology, groundwater, etc.)
Site investigation & findings
Key factors creating rock slides at Wabasha Street
• Remedial Actions
Topics for Today
CIVIL ● MANUFACTURING ● MINING ● OIL & GAS ● POWER GENERATION
May 30, 2018 Wabasha Street Rock Slide Slide 3
• Initial site visit, and development of an investigation plan
• Collect site geometry (photogrammetry and laser scanning)
• Collect information about the rocks and soil
Weathered limestone
Fresh limestone
Limestone joints
Shale character
Sandstone strength and joints
• Collect information about surface and groundwater
• Initiate a monitoring program
Site Activities Summary
CIVIL ● MANUFACTURING ● MINING ● OIL & GAS ● POWER GENERATION
May 30, 2018 Wabasha Street Rock Slide Slide 4
CIVIL ● MANUFACTURING ● MINING ● OIL & GAS ● POWER GENERATION
May 30, 2018 Wabasha Street Rock Slide Slide 5
Soil
Heavily Weathered Limestone
Limestone
Shale
Sandstone
Site Geology
Dry-Stack
Concrete “Walls”
CIVIL ● MANUFACTURING ● MINING ● OIL & GAS ● POWER GENERATION
May 30, 2018 Wabasha Street Rock Slide Slide 6
• These apply to past, recent and future rock slides:
Weathering and karst at geological time scale
Vertical joints and horizontal seams in the Platteville limestone
Likely quarrying of the Platteville limestone
Surface runoff
Shale and sandstone raveling (water & freeze/thaw)
Past attempts at slope stabilization on private property (dry stack, cables, etc.)
Key Factors at Wabasha Street Site
Surface &
groundwater,
freeze-thaw
Sandstone and
shale raveling
Limestone blocks are
undercut & topple off
Vertical joints form
limestone blocks
CIVIL ● MANUFACTURING ● MINING ● OIL & GAS ● POWER GENERATION
May 30, 2018 Wabasha Street Rock Slide Slide 7
• Sandstone/shale
raveling
The Key Factor
About 2’ limestone has
fallen off
Shale
CIVIL ● MANUFACTURING ● MINING ● OIL & GAS ● POWER GENERATION
May 30, 2018 Wabasha Street Rock Slide Slide 8
Current Status
Block
that fell Overhanging
block
CIVIL ● MANUFACTURING ● MINING ● OIL & GAS ● POWER GENERATION
May 30, 2018 Wabasha Street Rock Slide Slide 9
5 6 7
8
9
10 11
12
13
14
17 15
16 18 19
17 15
12
14
10
Limestone joints numbered
CIVIL ● MANUFACTURING ● MINING ● OIL & GAS ● POWER GENERATION
May 30, 2018 Wabasha Street Rock Slide Slide 10
Joints are dashed because the
length and orientation are uncertain
PRIVATE PROPERTY
PRIVATE PROPERTY
PRIVATE PROPERTY
Site Map
Block that fell in late April Overhanging block
CIVIL ● MANUFACTURING ● MINING ● OIL & GAS ● POWER GENERATION
May 30, 2018 Wabasha Street Rock Slide Slide 11
1. Limestone blocks
2. Upper (weathered) limestone
3. Limestone-shale-sandstone interface
4. Upper Soil
5. Lower Soil
6. Prior slope stabilization
Specific Site Features (Categorized into Types)
CIVIL ● MANUFACTURING ● MINING ● OIL & GAS ● POWER GENERATION
May 30, 2018 Wabasha Street Rock Slide Slide 12
Specific Site Features
1 1 1
1 1
6 2
3
4
5 5
CIVIL ● MANUFACTURING ● MINING ● OIL & GAS ● POWER GENERATION
May 30, 2018 Wabasha Street Rock Slide Slide 13
• Immediate threat treatment to permit Wabasha Street to be re-opened
• Longer-term treatment
Two Phases (at least)
CIVIL ● MANUFACTURING ● MINING ● OIL & GAS ● POWER GENERATION
May 30, 2018 Wabasha Street Rock Slide Slide 14
• Overhanging weathered
limestone, dry stack & soil above
recent block fall
Immediate At-Risk Features (immediate threat)
1a 1c 1b
2-4-6 2-4-6
• Overhanging limestone blocks
1a—Must be removed
1b, 1c—Likely to be removed (due to removal of 1a or because of instability)
Overlying weathered limestone, soil, dry stack, etc. also removed
CIVIL ● MANUFACTURING ● MINING ● OIL & GAS ● POWER GENERATION
May 30, 2018 Wabasha Street Rock Slide Slide 15
Considerations Leading to the Longer-Term Treatment
Soil
Limestone
Shale
Sandstone
Surface &
Ground
Water
Site Geometry Land
Ownership
Remedial
Actions
Service Life &
Maintenance Risk Cost Constructability
Monitoring Aesthetics
Landowner
Impacts
CIVIL ● MANUFACTURING ● MINING ● OIL & GAS ● POWER GENERATION
May 30, 2018 Wabasha Street Rock Slide Slide 16
CIVIL ● MANUFACTURING ● MINING ● OIL & GAS ● POWER GENERATION
Wabasha Street Rock
Slide
Slides prepared by Itasca Consulting Group May 30, 2018 Summarized for presentation by City of Saint Paul Public Works June 1, 2018