Research conducted by: Collin Martin, PE,CHMM, Luis Gonzalo Castro Diaz, EI and Nick Jenshak, Presented by: Collin Martin

1. RESEARCH POSTER PRESENTATION DESIGN © 2015
www.PosterPresentations.com
1. ABSTRACT
Soil vapor extraction (SVE) is one of the most commonly used technologies for
the remediation of unconsolidated soils impacted by chlorinated volatile organic
compounds (cVOCs). Most SVE remediation engineers incorporate an array of
site data, contaminant details, and remedial goals during their design process.
Foremost among these critical design criteria is having a comprehensive
understanding of the source area, contaminant distribution, subsurface vacuum
response, and lithologic complexities at the Site. Vadose zone soil grain size
analysis, effective porosity, pilot testing results, and soil cVOC concentrations are
routinely included as part of this design process. Even with this plethora of data,
many sites still fall victim to improperly designed remediation systems. In order
to help refine the SVE system design process, soil gas plume mapping was
evaluated for its ability to provide useful data regarding preferential airflow
pathways. An assessment of multiple sites with cVOC releases, pre-remedial soil
gas investigations, and SVE system operational data was conducted to determine if
pre-remediation soil gas mapping could yield beneficial design inputs for SVE
systems installed in unconsolidated vadose soils.
SITE #1: SOIL GAS PLUME WITH SVE ROI DISCUSSION
2. OBJECTIVE
EXAMPLE 2-D CROSS-SECTION FROM SITE #1
SITE #2: SOIL GAS PLUME WITH SVE ROI SITE #4: SOIL GAS PLUME WITH SVE ROIEXAMPLE 2-D CROSS-SECTION FROM SITE #2
EnviroForensics, LLC
Using Soil Gas Concentration Mapping to Predict Soil Vapor Extraction Radius of Influence Variances and Optimize Remedial System Design
Collin Martin, PE, CHMM, Gonzalo Castro Diaz, EI, and Nick Jenshak
SITE #3: SOIL GAS PLUME WITH SVE ROI
• The SVE system ROI overlay was compared against the soil gas plume to
determine how closely the concentration trends aligned with the vacuum
ROI extents.
• Multi-extraction well systems (Site #3 and #4) displayed a similar
degree of propagation similarity as single extraction well systems (Site
#1 and 2).
• System SCFM and applied vacuum was compared to ROI to determine if
higher or lower ratios affected similarity to the soil gas plume.
• Site #1: 396 SCFM – 5.5 in-Hg
• Site #2: 433 SCFM – 5.0 in-Hg
• Site #3: 210 SCFM – 9.5 in-Hg
• Site #4: 287 SCFM – 13.5 in-Hg
• It appears that lower applied vacuums (Site #1 and 2) yield more
symmetrical ROIs, while the volume of extracted air appears to have a
similar bearing on ROI symmetry.
• These same symmetrical traits appear in the soil gas plume for Site #1
and 2 as well.
• It appears that the subsurface characteristics governing the dispersion
and extents of soil gas also play an important factor in the propagation
of applied vacuum from SVE systems.
CONCLUSIONS
• Average shallow cohesive unit thickness of 7 ft.
• Average unconsolidated vadose unit thickness of 13.5 ft
• Average depth to water of 22 ft
• Grain size classification percentages:
• Sand and Gravel: 89%, Silt: 7%, Clay: 4%
• Average moisture content in soils: 9.6%
• Average shallow cohesive unit thickness of 6 ft.
• Average upper unconsolidated vadose thickness of 15 ft
• Average depth to water of 27 ft
• Average moisture content in soils: 9.6%
• The upper and lower cohesive units bound the soil gas
and SVE vacuum ROI in the vertical directions
• PCE was detected at a maximum concentration of
375,000 µg/m3 in the source area
• The soil gas plume has an area of roughly 173,494 ft2
(100 µg/m3)
• The SVE system ROI is roughly 152,053 ft2 (0.1 in-wt)
• The SVE applied vacuum is 9.5 in-Hg
• PCE was detected at a maximum concentration of
51,600 µg/m3 in the source area
• The soil gas plume has an area of roughly 66,051 ft2
(100 µg/m3)
• The SVE applied vacuum is 5.5 in-Hg
• The SVE system ROI is roughly 80,424 ft2 (0.1 in-wt)
• PCE was detected at a maximum concentration of
1,400,000 µg/m3 in the source area
• The soil gas plume has an area of roughly 180,955 ft2
(1,000 µg/m3)
• The SVE applied vacuum is 13.5 in-Hg
• The SVE system ROI is roughly 196,349 ft2 (0.1 in-wt)
• PCE was detected at a maximum concentration of
1,480,000 µg/m3 in the source area
• The soil gas plume has an area of roughly 1,583,362 ft2
(100 µg/m3)
• The SVE applied vacuum is 5.0 in-Hg
• The SVE system ROI is roughly 125,663 ft2 (0.1 in-wt)
This analysis was conducted to evaluate if a consistent, predictive pattern could be
determined to link soil gas plume behavior with SVE vacuum ROI. If found, this
predictive data could be used to help refine SVE system designs for sites with
limited site-specific data or those where SVE pilot testing was not possible.
3. LITHOLOGIC CHARACTERISTICS
Representative sites were evaluated based upon the following criteria:
1) Specific lithologic patterns, consisting of a cohesive surface cap underlain by
unconsolidated vadose zone soils.
2) The similarity of soil characteristics (moisture content, grain size, etc.)
3) The completion of a pre-remedial soil gas investigation.
4) The installation and operation of an SVE system affecting the unconsolidated
vadose zone soils.
Sites were screened out from this analysis if multiple source areas were identified,
significant down-gradient off-gassing from groundwater was present, or
inadequate soil gas, lithologic, or SVE system data was collected.
3. EVALUATION CRITERIA
Representative sites were evaluated based upon the following criteria:
• The shallow cohesive unit across all Sites yielded an average thickness of
approximately 11.5 ft, ranging from a minimum of 6 to a maximum of 18 ft.
• The average thickness of the unconsolidated vadose units was 14.5 ft, ranging
from 13.5 to 15 ft.
• The average depth to water across all Sites was 24 ft, ranging from a minimum
depth of 22 to a maximum of 30 ft.
• The average (and ranges) of the grain size classification percentages are as
follows:
• Sand and Gravel: 89.6% (85.9 - 95%)
• Silt: 5.75% (<1 – 9.9%)
• Clay: 5.3% (2.8 – 7.7%)
• The average moisture content in soil samples collected from the
unconsolidated vadose soils was 7.78%, with values ranging from 3 to 17%.
While not strong enough to replace pilot testing data, soil gas plume mapping
can provide indicators for anticipating non-uniform vacuum propagation in the
subsurface, which can be beneficial during extraction well placement and
airflow, vacuum, and blower sizing.
Collin Martin is a Senior
Engineer and Technical Group
Manager at EnviroForensics, and
has over 14 years of diversified
professional experience in
environmental consulting. He has
a focus in remedial technology
assessment, mechanical system
design, and remediation
implementation oversight. He has
designed and implemented over
20 remediation systems using a
variety of remedial technologies,
including air and ozone sparging,
hydraulic fracturing, soil vapor
extraction, multi-phase extraction,
and thermal remediation. Mr.
Martin has experience in all
phases of remediation planning,
feasibility studies, pilot testing,
and mechanical system data
analysis and optimization efforts.
BIOGRAPHIES
Nick Jenshak is a Staff Geologist
with EnviroForensics and has over
two years of experience in
environmental consulting, with a
focus on site assessments, vapor
intrusion investigations, and data
evaluation. He has performed
extensive site investigation and
delineation studies, including soil
gas assessments at over 25 sites
throughout Indiana. Mr. Jenshak
has performed vapor intrusion
investigations, comprising of
indoor air and sub-slab vapor,
vapor intrusion mitigation
installation; research; data analysis
and interpretation; and preparation
of technical reports.
Luis Gonzalo Castro Diaz is a
Staff Engineer with
EnviroForensics. Mr. Castro Diaz
has a Bachelor’s Degree in Civil
Engineering from Valparaiso
University, is an Engineering
Intern in the State of Indiana, and
is fluent in Spanish, French, and
English. He has over 2 years of
professional consulting experience
performing site investigations,
remediation system installation,
operation, and maintenance
activities, remedial progress
sampling, preparation of technical
reports, excavation oversight, and
discharge permitting.