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ANALYSIS
Poster Session
Soil
Vapor Analysis to Document Solvent Contamination Sources,
Contaminant Plume Geometry, and Evidence of Dehalogenation
Vanessa A. Gallo, Stephen E. Posten, AMEC Earth and
Environmental
A comprehensive passive soil vapor survey was performed
at a former office equipment manufacturing facility
(currently an active carton manufacturing facility) using
W.L. Gore & Associates Gore-Tex® (ePTFE)
membrane modules. Prior use of two sub-grade vapor
degreasing units within the center of the plant production
area had resulted in uncontrolled discharge of
trichloroethene (TCE) and 1,1,1-trichloroethane (TCA) to
the subsurface. The objective of the soil vapor survey was
to: (1) document the vapor concentration distribution
underlying the production building slab, (2) identify
potential residual contaminant source areas in soil, and
(3) verify ground water contaminant plume geometry. A
total of 91 ePTFE modules were installed using slam bars
to a depth of 2-3 ft below ground surface along a grid
node spacing of 25 ft. The grid extended from the center
of the production building to the exterior property
boundary. Concrete coring and power auger equipment was
required to reach target installation depths below the
concrete building slab. The membranes were recovered 10
days after installation and analyzed via GC/MS for
chlorinated hydrocarbons by W.L. Gore & Associates.
The results of these analyses indicated a fairly uniform
elevated TCE and TCA vapor distribution below the building
slab, with several distinct zones of maximum sorbed
solvent vapor mass. These data defined the scope of work
for subsequent indoor ambient air monitoring and targeted
subsurface soil investigation. Exterior to the production
building, the vapor data clearly defined a narrow ground
water contaminant plume extending off-site. The presence
of 1,2-dichloroethene only in samples obtained adjacent to
a wetland near the property boundary supported prior
limited data suggesting solvent dechlorination in these
anaerobic, organic carbon-rich soils.
Core
Analysis: Is it a Good Indicator of Metal Release and
Capping Efficiency?
Chunhua Liu, Gradient Corporation, Jenny A. Jay, Tufts
University, Timothy E. Ford, Harvard School of Public
Health.
Analysis of core samples is commonly used to detect
contaminant transport from capped sediments. This paper
evaluates the effectiveness of the core analysis technique
as an indicator of metal release and capping efficiency.
The laboratory experiment was designed to evaluate the
metal concentration profile in capped sediment and capping
material in relation to metal flux to the overlying water.
Results suggested that metal concentration gradients in
the sediment or capping material may not be good
indicators of metal transport, especially under conditions
of advective flow.
The
Sequestering of Volatile Organic Compounds in Sediment
Samples: A Time Line Comparison of Method 5035 High-Level
vs. Low-Level
Elizabeth M. Porta, Peter J. Kane and Amy Jo Arndt, The
Woods Hole Group, Inc., Nancy C. Rothman, Ph.D., New
Environmental Horizons, Inc., Charles A. Menzie, Ph.D.,
Menzie-Cura & Associates, Inc.
Samples were collected for volatile organic analysis
via Method 5035 into deionized water and methanol. The
deionized water low-level samples were analyzed within
7-days of collection. After six months of cold storage at
4°C, the high-level methanol aliquots were analyzed. The
results obtained of key target compounds are compared over
a 6-month time line. This study shows that a bias exists
between the low and high-level results. Volatile organics
can be sequestered in some sediment samples and this could
impact decision making during risk assessment, and
possibly underestimate the risk posed by the sediment.
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