(LIF) to Establish in the of · 2019-11-14 · LNAPL – Common Misconceptions Misconception...
Transcript of (LIF) to Establish in the of · 2019-11-14 · LNAPL – Common Misconceptions Misconception...
Laura Jones Golder Associates Ltd.
Using Laser Induced Fluorescence (LIF) to Establish Monitoring Well Network of Migrating LNAPL Plume in the Vicinity of Surface Water
www.vertexenvironmental.ca
SMART RemediationToronto, ON
January 29, 2015
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Using LIF to Establish Monitoring Well NetworkFormer Michigan Avenue LandfillFebruary 13, 2015
Presented By:Laura Jones, M.A.Sc., P.Eng.
Presentation Outline
Site History
Overview of LNAPL (oil) behaviour
LIF Background
LIF Investigation and Results
Current Monitoring Well Network
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Former Michigan Avenue Landfill
Historical Setting
Sarnia Observer, March 6, 1931
1952
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Extent of LNAPL – 1999 Lake Chipican
Inferred LNAPLExtent
Confirmed LNAPLExtent
Timeline
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LNAPL – Common Misconceptions
Misconception Conceptual Framework
LNAPL enters the pores as easily as groundwater.
Capillary pressures and multiphase flow (air, water, NAPL) affects migration
All the LNAPL is recoverable LNAPL is only recoverable when the LNAPL transmissivity is high enough
Pores in an LNAPL zone are at 100% saturation
LNAPL saturation function of soil type, generally less than 40%
LNAPL floats on the water table like a pancake
LNAPL is distributed like a shark fin with the highest saturation near water table
If LNAPL thickness increases, it means the LNAPL zone is advancing.
LNAPL thickness changes with water table fluctuations
LNAPL spreads in the direction of groundwater flow.
LNAPL spreads based on the LNAPLdriving head
LNAPL continues to migrate over long periods of time.
Due to capillary forces and reduced LNAPLdriving head, LNAPL migration generally ends a few years after a release
LNAPL Site Conditions
Inferred source area associated with oily clay-rich material in lowland swampy areas in northwestern portion of former landfill
Oil present since 1920s-1944 (at least 80 years old)
Migration beyond source area within fill material and native sand deposits
Limited potential for on-going migration unless significant hydraulic changes (e.g., historical low lake levels in Lake Huron)
LNAPL investigations/remedial actions have focused on leading edge
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Laser Induced Flouresence
LIF involves emitting a laser pulse via fiber optic line and subsequent capture of induced fluorescence via separate optic line to measure peak wavelength and intensity.
Molecules of hydrocarbons in the soil first absorb light – then fluoresce.
PAHs present in hydrocarbons facilitate NAPL identification.
Lighter compounds (e.g., gasoline) tend to fluoresce at shorter wavelengths vs. heavier compounds (e.g., motor oil).
shortUV
longUV
kero
sene
gaso
line
dies
el
oil
(Dakota Technologies)
Sample LIF Profiles
“Clean” “Motor Oil Impacted” “Diesel Impacted”
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Results of 2012/2013 LIF Investigations
2012 Investigation
2013 Investigation
Seasonal Water Body
LNAPL Discovered October 2012
LNAPL Discovered November 2013
Borehole and Well Installation November 2012
Ponds
2011 Sheet Pile
2012 Sheet-pile
Timeline – October 2011 to Present
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2014 LIF Investigation
Preliminary 3D Visualization
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Current Monitoring Well Network
Summary
LNAPL present from historical operation of a landfill and deposition of oily wastes from a refinery
LNAPL is migrating towards surface bodies in the vicinity of Lake Chipican (both permanent and seasonal)
LIF was used to establish the current foot print of LNAPL and establish a network of sentry wells
Sentry wells provide advanced warning of LNAPL migration to protect surface water
Traditional delineation methods would have used a larger grid size and could have missed narrow finger plume of LNAPL migrating northwards (less than 15 metres wide)
LIF investigation was used to develop remedial action plan prior to LNAPL migration to surface water with consultation with the client and the Ministry of the Environment and Climate Change
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Questions?
Lake Huron – Historical fluctuations