The 3D conceptual site model revealed that LNAPL from the former retail gasoline station had penetrated deep into the source area and migrated hundreds of feet south through semi-confined permeable layers below the water table, despite groundwater flow being predominantly to the north. High resolution site characterization tools, including optical profiling and membrane interface probing, were used to map LNAPL fluorescence and dissolved phase VOCs. When combined with additional site data in a 3D model, it provided insight into LNAPL and plume migration through confined areas not evident from traditional site investigations.

1. Rocky Mountain Region
Denver, Colorado
(303) 277-1694
Gulf Coast Region
Houston, Texas
(281) 310-5560
3D Conceptual Site Model (CSM)
Utilizing Data From High Resolution
Site Characterization (HRSC) Tools
Former Retail Gasoline/Diesel Station Release
Click on the comment
balloons in this corner
where they appear
for more details

2. A 3D Conceptual Site Model (CSM) Utilizing Data From a High Resolution Site Characterization
(HRSC) at a Former Retail Gasoline/Diesel Station Release
BACKGROUND: The former retail gasoline station (circa 1960-1990) site is located in a small town, in an agricultural area. The site is in
a state lead UST program for monitoring and remediation. The release was confirmed in 1989, (possibly both diesel and gasoline,)
and the ASTs, USTs, and dispenser islands were removed in 1993. The groundwater gradient was mapped in a low and high season,
with flows to the north towards a major river. Soil vapor extraction and air sparging (SVE-AS) was performed on the site from 1999 to
2013. SVE-AS pilot tests in 2016 determined that continued SVE-AS would not be effective. Despite having predominant groundwater
flow to the north, high BTEX and TVPH concentrations had been measured in soil cores and monitor wells significantly south of the
source area. These high concentrations indicate the presence of LNAPL, despite the lack of LNAPL presence in the monitor wells.
Property access for the HRSC survey was limited to the site itself, and a parcel of vacant land to the south of the site.
SCOPE OF WORK: The HRSC survey included first investigating the LNAPL distribution using the Optical Image Profiler (OIP-UV) tool to
map fluorescence of the LNAPL. Then, beyond the mapped LNAPL, the dissolved phase VOCs and hydraulic conductivity were
mapped using the Membrane Interface/Hydraulic Profile Tool (MiHpt). Confirmation borings were also conducted using direct-push
dual-tube coring methods, to collect soil samples adjacent to the HRSC borings for comparison. Elevations of all boring locations were
measured.
SUMMARY OF RESULTS: The following slides show the construction of a 3D model, using the high resolution data, ground water
elevations, and other site data, that reveals the LNAPL penetrated quite deep in the source area, and migrated in semi-confined
permeable layers, well below the water table, several hundred feet south of the site.
Special Thanks to CGRS Inc. for providing the site
background data and significant input into the report.

3. 2D MiHpt & OIP-UV
Survey Map
• A classic 2D Bubble map is used to display
maximum values at each log boring, results in
mapping the lateral extent of the plume.
• Source area is a UST release in the site on the
north side of the highway. (green property
outline)
• Parameters Displayed:
• Max. MIP-PID (uV) - diamonds
• Max. OIP-UV %Fluorescence - circles
• Data Collected
• 51 OIP/EC Borings
• 18 MiHpt/EC Borings
• 10 Confirmation Soil Core Borings
SB-MIP-04
SB-MIP-10
SB-MIP-12
SB-MIP-17
SB-OIP-11
SB-OIP-25
SB-OIP-27
SB-OIP-39
SB-OIP-44
SB-OIP-47
MIP-01
MIP-02
MIP-03
MIP-04
MIP-05
MIP-06
MIP-07
MIP-08
MIP-09
MIP-10
MIP-11
MIP-12
MIP-13
MIP-14
MIP-15
MIP-16
MIP-17
MIP-18
OIP-01
OIP-02
OIP-03
OIP-04
OIP-05
OIP-06
OIP-07
OIP-08
OIP-09
OIP-10
OIP-11
OIP-12
OIP-13
OIP-14
OIP-15
OIP-16
OIP-17
OIP-18
OIP-19
OIP-20
OIP-21
OIP-22
OIP-23
OIP-24
OIP-25
OIP-26
OIP-27
OIP-28 OIP-29
OIP-30
OIP-31
OIP-32
OIP-33
OIP-34
OIP-35
OIP-36
OIP-37
OIP-38
OIP-39
OIP-40
OIP-41
OIP-42
OIP-43
OIP-44 OIP-45
OIP-46
OIP-47
OIP-48
OIP-49 OIP-50OIP-51
3526100 3526150 3526200 3526250 3526300 3526350 3526400 3526450 3526500 3526550 3526600 3526650
134145013415001341550134160013416501341700134175013418001341850134190013419501342000
0 50 100 150 200
Scale (feet)
MIP Maximum PID µV Response
1.0E+05 uV to 2.5E+05 uV
2.5E+05 uV to 5.0E+05 uV
5.0E+05 uV to 1.0E+06 uV
1.0E+06 uV to 1.0E+07 uV
1.0E+07 uV to 4.3E+07 uV
OIP Max %Fluorescence
0% to 0.1%
0.1% to 5%
5% to 10%
10% to 50%
50% to 80%

4. 3D Conceptual
Site Model Inputs
• Surface Height Elevation model from all
boring locations (shown on right)
• Monitor Wells
• High Water Table Elevation
• Low Water Table Elevation
• OIP-UV Soil Borings
• Electrical Conductivity (EC)
• % Area Fluorescence (%AF)
• MiHPT Soil Borings
• EC (from both MiHPT and OIP logs)
• MIP (PID, FID, XSD)
• HPT (Pressure & Flow)
• Confirmation Soil Borings
• Laboratory Data (TVPH, mg/kg) N

5. Ground Water
Elevation Models –
High Season
• High ground water level in
August
• Gradient shows generally north
to northwest trend, towards a
major river system about 3 miles
north of the site.
• No monitor wells were present
in the south 1/3 of the study
area to model ground water
elevation.
N

6. Ground Water
Elevation Models –
Low Season
• Low ground water level in April.
• Gradient still shows generally
north trend, towards a major river
system about 3 miles north of the
site.
• Significant irrigation activity in the
area may have short term
intermittent affects on ground
water flow direction.
N

7. LNAPL Plume &
Low Ground
Water Table
• Low ground water level Height Field
• Top view of >0.1% Area Fluorescence
Iso-surface to show LNAPL lateral
extent.
• Notice narrow zone in center of site.
• Shows amount of LNAPL that is above
the lower water table boundary near
source area (brighter magenta at
north end of map)
• Most LNAPL resides confined below
the lower water table and has
migrated south, counter to ground
water flow, which is north.
N

8. Monitor Well Renderings & Groundwater
Elevation Models (High & Low Season)
N

9. OIP-UV Boring Renderings Displaying % Area
Fluorescence (%AF)
N

10. MiHpt Boring Renderings Displaying Dissolved VOCs
via PID Response (uV) from MIP Detectors
N

11. Confirmation Soil Borings and Lab Data (TVPH)
Rendering
N

12. Combined OIP (%AF) and MiHpt (PID uV)
Boring Renderings
N

13. Isosurface Model > 0.1% Area Fluorescence
N

14. Adding Dissolve Phase VOCs (MIP-PID) Response
N

15. EC Rendering on OIP Borings & HPT Pressure
Rendering on MiHpt Borings
N

16. Isosurface Model of HPT Pressure >50 psi
(Low Permeability Zones)
N

17. Combined Isosurface Models & Boring Renderings
Showing Migration of LNAPL and VOCs through Confined
Layers
N

18. Combined Isosurface Models & Boring Renderings Using
Orthographic View (Non-Perspective)
N
Low Season Water Table
High Season Water Table