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Techniques for Developing High Resolution Light Non-Aqueous Phase
Liquid (LNAPL) Conceptual Site Models
Roger Lamb, R.G – Roger Lamb Consulting
Presented by:
High Resolution LCSM Investigation Tools• MIHPT – Detects VOCs in Fresh Gasoline, Jet Fuel, Weathered
Gasoline, EDB, MtBE and provides Qualitative Permeability and Hydraulic Conductivity Estimates.
• uVOST/LIF – Detects LNAPL containing PAHs in ppm concentrations – 10 to 500 ppm.
• Optical Imaging Profiler (OIP)– Detects LNAPL containing PAHs and photos of the subsurface soils.
• Collaborative soil, groundwater, soil vapor analytical results and lithologic data sets – Field Analysis Preferred.
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MIHPT Diagram
Depth Detector
MiHpt Transfer
Line
Drill Rods
Electrical Generator
(self sufficient)
Ultra Pure Compressed Gases
4
Collaborative Data Set General RecommendationsSoil Samples – Cohesive Deposits• Collect from target depths/locations based on direct sensing tool results- low,
medium, high detector response - minimum 30 samples.• Collect soil cores using closed-tubed sampling tools, maximum core length of
1 foot.• Use Encore samplers or similar to collect soil samples from the soil cores.• Document soil lithology and depth interval from which Encore samples are
collected.• Include in soil analysis TPH-GRO or DRO or similar depending on State
requirements - Field Analysis Preferred.
Ground Water/ Soil Vapor Samples• Install piezometers/wells/etc. based on based on direct sensing tool results-
low, medium, high detector response. • Use short screens, maximum length 5 feet for groundwater, 1 foot for soil
vapor.
Economic Benefits
Reduction in investigation costsIncrease in investigation data set
Increase in speed of decisions
Collected over 15 years Collected over 4 days
Total 2,255 Total 13,545
Conventional Tools High Resolution Tools
Average Site
Conventional Tools
Collected over 16 years
Total 3,568
High Resolution Tools
Collected over 10 daysTotal 27,818
Large Site
Technical Benefits
Hydrogeologic CharacterizationLNAPL Body Distribution
Remediation Feasibility/Design
Hydrogeologic CharacterizationRisk Assessment
Remediation Feasibility/MonetizationRemediation Pilot Testing, Design, Implementation
Soil Electrical Conductivity-Alluvial Deposits
ClaysClays
Topsoil
UST Pit
Sand Layers
Soil Electrical Conductivity-Alluvial Deposits
UST Pit
Alluvial Clays
Alluvial Sands
Hydraulic Profiling Tool- Alluvial Deposits
Permeability decreasing with depth
Hydraulic Profiling Tool- Limestone Residuum
highly variable permeability
Hydraulic Profiling Tool- Saprolite
High Resolution Hydraulic Conductivity Estimates
High K Zones
LNAPL Body DistributionSource Determination
Risk AssessmentRemediation Feasibility/Monetization
Remediation Pilot Testing, Design, Implementation
Benzene in Ground Water
Former UST PIT
Ground Water Surface
LNAPL Migration in Sand Layers
X-section MIP PID Data Set
Mobile Phase LNAPL in Monitoring Wells
X-section uVOST Data Set
Isopach Map - uVOST Data Set
Total BTEX in Ground Water
Core of
LNAP P
lume
Plan-view MIP FID Data
X-section MIP FID Data
X-section MIP FID Data
Some Lessons LearnedMonitoring wells do not need to be screened across the groundwater surface to detect mobile phase LNAPL.
LNAPL migrates to depths tens of feet below the groundwater surface.
LNAPL releases of different physical properties do not mix in the subsurface environment.
MIP PID/FID sensors indicate gasoline LNAPL at 30 feet
Monitoring well screened 27 to 32 feet contains mobile LNAPL
Monitoring well screened 15 to 25 feet does not contain LNAPL
Groundwater surface at 14 feet
MOBILE Phase LNAPL
X-section MIP FID Data
Develop Initial LNAPL CSM
• Establish Desired Results with Stakeholders.
• Fuel Types and Age of Releases – Weathered Gasoline, Fresh Gasoline, Diesel, Waste Oil.
• Hydrogeologic Data – Glacial/Alluvium/Cherty Clays.
• Map Mobile LNAPL – LNAPL that accumulates in wells.
• Map Soil and Groundwater Analytical Results – Above 1ppm Benzene which is indicative of LNAPL.
• Establish what results actually be achieved based on the initial LCSM.
Initial LCSM Considerations
Fold into the LCSM current understandings of:
• Residual/Mobile/Migrating LNAPL
• LNAPL Transmissivity
• LNAPL Biodegradation
• Vapor Intrusion
• Environmental/Remediation Hydrogeology
LCSM Field Investigation Design
Critical Field Design Considerations
1. Geologic Condition Issues- Cherty Soils or Shallow Bedrock.
2. Concrete Pavement – Have Coring Tools Onsite.
3. Weathered Gasoline – MIHPT system only
4. Leaded Gasoline – An MIHPT with and ECD Detector.
5. Inside Building or Tight Locations – Determine if accessible by contractors equipment.
6. Offsite Access - Plan for it based on initial LCSM.
7. Potential Impact of Offsite Chemical Releases.
Start with Anchor Points - Advance Direct Sensing Tools next to 3 to 6 sample locations that having the one of the following characteristics:
1. Has Contained LNAPL.2. Groundwater Results over 1 mg/L Benzene or Naphthalene.3. Soil Results over 1 mg/kg Benzene or Naphthalene.4. Is of Interest Based on Potential Receptors or Other Factors.5. Naphthalene concentrations at ppm concentrations in soil
or groundwater samples is a positive indication that the uVOST/LIF or new OIP tool will detect the LNAPL.
Proposed LIF or MiHPT soundings locations
LNAPL In Well
uVOST/MIP determination soundingsLNAPL delineation soundings
Implement LCSM Field Investigation
1. As high resolution data is collected, update the LCSM in real-time with focus on the project goals and determining what result(s) can be guaranteed.
2. Quickly determine if the uVOST/LIF is detecting the LNAPL.
3. Ensure all project stakeholders are updated to changes in the LCSM in real-time if possible and at a minimum daily. The whole technical project team must be updated in real-time.
4. Look for indicators of chlorinated solvents in the MIP sensor data either the ECD or XSD.
5. Fold into the real-time analysis modern LNAPL science and hydrogeology.
Mobile Phase LNAPL measured in monitoring well or bailer
Residual Phase LNAPL -Benzene Conc.
Completed MiHPT sounding with ID number as of 12/7
Figure 1 – Completed MiHPT as of 12/7
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10 11
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A
A’B
B’C
C’
Daily MIHPT Log Analysis Using DI Viewer Software
A A’
LNAPL Impact assumed if PID sensor values are over 1,000,000 uV.
Screen Shot of Smart-Data Solutions Website
Crunch Data Set Focused on Project Goals
• Project Business Goals – Redevelop a property impacted by an historical gasoline release.
• Technical Goals - Define extent of gasoline release above 2 mg/kg benzene action levels to aid in excavation design.
• Site Conditions – Historical gasoline release into residuum derived from cherty limestone.
• Investigation Design/Cost – uVOST and MIHPT - investigation depth 25 feet, 5 days of work, total direct sensing cost – $25,000.
• Investigation Results – uVOST failed to detect weathered gasoline LNAPL, MIHPT delineated onsite extent of weathered gasoline LNAPL and hydrogeologic conditions.
Case 1 – Excavation Feasibility/Monetization
MIHPT sounding locations in area of proposed soil excavation
Spatial analysis of MIP PID sensor readings
Residual soils decreasing in permeability with depth
MIP PID sensor readings in excess of 1,000,000 uV indicative of LNAPL impact
Collaborative Soil Sample Locations
Estimated volume of soil containing benzene in excess of the 2mg/kg action level – 460 cubic yards.
Project Business Goals – Determine why remediation system had not met project goals after 6 years and $700,000.
Technical Goals - Define extent of LNAPL and determine if remediation wells properly screened.
Site Conditions – Historical diesel, gasoline and kerosene releases into alluvial deposits.
Investigation Design/Cost – uVOST and MIHPT - investigation depth 20 feet, 4 days of work, total direct sensing cost – $20,000.
Investigation Results – uVOST detected diesel/kerosene LNAPL, MIP detected weathered gasoline LNAPL, HPT defined hydrogeology.
Case 2 – Remediation System Optimization/Monetization
Extent of Mobile Phase LNAPL measured in monitoring wells
Extent of Diesel and Kerosene LNAPL based on uVOST
Extent of Mobile Phase LNAPL measured by monitoring wells
Extent of Weathered Gasoline LNAPL Based on MIP PID
Extent of Mobile Phase LNAPL measured by monitoring wells
Extent of Weathered Gasoline LNAPL Based on MIP PID
Extent of Diesel and Kerosene LNAPL based uVOST
Project Business Goals – Guarantee plume of gasoline impacted ground water stops migrating offsite.
Technical Goals - Define extent of residual phase gasoline LNAPL, define Hydrogeologic conditions and develop mass flux estimates.
Site Conditions – Historical gasoline releases into saprolite.
Investigation Design/Cost –MIHPT primarily with some uVOST - investigation depth 40 feet, 10 days of work, total direct sensing cost – $50,000.
Investigation Results – MIHPT define residual phase gasoline LNAPL and hydrogeologic conditions allowing for mass flux estimates, uVOST failed to detect weathered gasoline LNAPL. MIP ECD also detected EDB in LNAPL.
Case 3 – Remediation System Design/Monetization
Ethylene Dibromide in LNAPL
Sample locations used in Mass Flux Calculation
HPT Injection pressure through mass flux assessment area
High Resolution Hydraulic Conductivity Estimates
High K Zones
Calculated Mass Flux – 18 lbs/day gasoline VOCs
