Applied Geology: Assessing and
Mitigating Geological Risks in a Modern
World
Leif Johnson, P.G.
Barr Engineering Company
Minneapolis
Everything you ever wanted to know about Geological
Hazards but were too asleep to ask.
Summary of Geohazards
1. Earthquakes
2. Volcanoes
3. Landslides
4. Floods
5. Karst
Geological Hazards: What do we do?
1. Look up
2. Stay out of the way
3. Build a “wall”
“Frequency of Magnitude”- (i.e how often does something happen?)
Earth is 4,600,000,000 years old
Humanoids are 2,000,000 years old
Human History is ~30,000 years old
Timescale of Hazards: long vs. short
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Flash Flood
Landslides
Earthquakes
Volcanoes
• Slope Creep
• Karst
• Floods (Prediction)
Short - Geology vs. Weather?
Duluth 2012 Flash Flood: Lots of Rain, real quick
Longer timescale – watching the grass grow?
Earthquakes: find the bulls eye…
Applied Geology
Applied Geology: Wind Farms
Applied Geology: Desktop Study
Desktop Study: Maps, Maps, Maps!
Desktop Study: Drill Logs
• State Geological
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Surveys
County Well Index
USGS Groundwater
Studies
Oil and Gas
Mineral Exploration
Desktop Study: Cross-sections
Applied Geology: Investigation
• Field Investigation
₋ Surficial deposits
₋ Bedrock
₋ Groundwater
₋ Man made
• Drilling holes
Applied Geology: Data collection
• Subsurface methods
₋ Geoprobe, Sonic, hollow
stem auger, mud rotary,
air rotary, rock coring,
cone penetration
testing
• Collect soil and/or rock
samples
Applied Geology: Instrumentation
• Many options
⁻ Inclinometer
⁻ Piezometer (fully
grouted, standpipe,
vibrating wire)
⁻ Packer testing
⁻ Pressure meter
Applied Geology: build a foundation
Geological Hazards: Slope Failure
Slope Failure: many kinds
• Landslides – soil+water
• Rock falls - boulders
• Undercutting – waterfalls,
shoreline erosion
• Mass wasting (avalanches)
Slope Failure: Recent Examples
• 2013 Bingham Canyon Mine Utah (probably
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largest, non-volcanic landslide in history)
2014 Oso Mudslide, Washington (42 confirmed
dead, 50+ structures destroyed)
2013 Rockville, UT- Rock fall kills two people in
their house
2012 Lilydale Park, St. Paul – two students killed
while on a field trip
Slope Failure: Bingham Canyon Mine
Slope Failure: Oso, Washington (Before)
Slope Failure: Oso, Washington
Slope Failure: Oso, Washington
Slope Failure: Rockville, UT
Slope Failure: Rockville, UT
Slope Failure: Lilydale Park, St. Paul, MN
Slide Area
Slope Edge
Geological Hazards: Floods – Multiple causes
• The “geo’s” – geography and geological reasons
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for landform creation
Historic Settlement – transportation and
settlement developed along rivers
Economic – flood plains have rich farm land
Man-made constraints – levees and dams
artificially control a natural process
Geological Hazards: Floods and FEMA Maps
Geological Hazards: Floods and FEMA Maps
• Zones (A, Axxx) – based on elevation of flood
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plain to a max elevation
10, 100, 500-year flood events
⁻ A statistical prediction that there is a 1% (0.2%
for 500-yr) chance an event might occur over a
set time
Geological Hazards: Loess
• What is it?
⁻ Wind-blown silt (particle size smaller than
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sand, but coarser than clay)
Why is a hazard?
⁻ Susceptible to collapse – pore spaces have
lots of air
Geological Hazards: Loess - Formation
Geological Hazards: Yellowstone
Geological Hazards: Yellowstone – Hot Spot
Geological Hazards: Yellowstone – Hot Spot
Geological Hazards: Yellowstone – Ash cloud
Geological Hazards: Yellowstone – Run?
Geological Hazards: Earthquakes
• Most common along plate tectonic boundaries
• Occur near active geothermal areas – hot spots
• Occur in areas of “re-activated” ancient faults•
New Madrid Fault zone, Virginia 2011
Man-made? – Oklahoma since 2010, dramatic
increase in earthquake activity, possibly related
to water injection wells
Geological Hazards: MN Earthquakes
Geological Hazards: MN Earthquakes
Geological Hazards: Karst
Geological Hazards: Karst
Geological Hazards: Mitigation
• “Look up” – understand elevation
changes, slope failure potential
• “Stay out of the way”- zoning
requirements (earthquakes, floods)
• “Build a wall” – levees, dams, piles, deep
foundations, sheet piles
Mitigation – Sheetpiles example
Geological Hazard Careers
• Geologist
• Engineering Geologist/Geological
Engineer
• Civil Engineer
⁻ Geotechnical Engineer
⁻ Structural Engineer
⁻ Water Resources Engineer
Applied Geology: Assessing and
Mitigating Geological Risks in a Modern
World
QUESTIONS?
Leif Johnson, P.G.
Barr Engineering Company
Minneapolis