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Technical Capabilities
375 Morgan Street Phoenixville, Pennsylvania 19460 Telephone 610.933.1900 |
Conceptual Modeling
The figure to the right is a view through a 3-dimensional model of the Lockport
Bedrock in Niagara Falls, NY. The original site conceptualization included three
hydraulic zones monitored by Upper, Middle, and Lower Zone wells (blue,
green, and red, respectively). This monitoring network could not demonstrate
effective hydraulic containment. SEI researched publications by the New York
State and United States Geologic Surveys. These documents identified eleven
discrete flow zones in the Lockport bedrock. These flow zones are thin, bedding
parallel fractures. Geophysical investigations, borehole video logging, and
packer testing located the flow zones at the site. Statistical analysis of the data
demonstrated the elevations of the flow zones could be predicted within about
2 feet by assuming that all of the zones were parallel planes. To monitor flow
zones, many existing wells were retrofit with 1-inch diameter piezometers with
2 feet of screen and a total of 3 feet of sand pack. This piezometer design
allowed installation of conventional water-level monitoring transducers and
sampling with conventional equipment.
The site conceptual model was revised to reflect the multiple flow zones and the
regulatory agency accepted the recharacterization. The agency approval moved
the site from the investigation phase into an O&M phase, and the site is
currently being delisted.
The figure to the right is a view through a 3-dimensional model of the Lockport
Bedrock in Niagara Falls, NY. The original site conceptualization included three
hydraulic zones monitored by Upper, Middle, and Lower Zone wells (blue,
green, and red, respectively). This monitoring network could not demonstrate
effective hydraulic containment. SEI researched publications by the New York
State and United States Geologic Surveys. These documents identified eleven
discrete flow zones in the Lockport bedrock. These flow zones are thin, bedding
parallel fractures. Geophysical investigations, borehole video logging, and
packer testing located the flow zones at the site. Statistical analysis of the data
demonstrated the elevations of the flow zones could be predicted within about
2 feet by assuming that all of the zones were parallel planes. To monitor flow
zones, many existing wells were retrofit with 1-inch diameter piezometers with
2 feet of screen and a total of 3 feet of sand pack. This piezometer design
allowed installation of conventional water-level monitoring transducers and
sampling with conventional equipment.
The site conceptual model was revised to reflect the multiple flow zones and the
regulatory agency accepted the recharacterization. The agency approval moved
the site from the investigation phase into an O&M phase, and the site is
currently being delisted.
Geologic Visualization
Visualization of site geologic conditions is often difficult. Software is
available to develop excellent 3-dimensional models, as shown here.
However, for most sites there are too few data points to allow the
software to properly interpret the geology. Historically, geologists have
incorporated professional interpretation of a limited data set based on
training and experience. Incorporating this professional interpretation
into 3-dimensional computerized models requires the definition of
"control points," defining the geology where there are no data. While
this is exactly what occurred with old fashioned hand drawings, there
are many in the community that refuse to "cheat" by adding control
points to a computer model. SEI believes in incorporating their
professional expertise into computerized models, exactly as we did in
the past with pen and paper.
Visualization of site geologic conditions is often difficult. Software is
available to develop excellent 3-dimensional models, as shown here.
However, for most sites there are too few data points to allow the
software to properly interpret the geology. Historically, geologists have
incorporated professional interpretation of a limited data set based on
training and experience. Incorporating this professional interpretation
into 3-dimensional computerized models requires the definition of
"control points," defining the geology where there are no data. While
this is exactly what occurred with old fashioned hand drawings, there
are many in the community that refuse to "cheat" by adding control
points to a computer model. SEI believes in incorporating their
professional expertise into computerized models, exactly as we did in
the past with pen and paper.
Groundwater Geochemistry
Often overlooked in environmental investigations are the conventional major ion
parameters. The major ions, while no contaminants, can be useful in assessing
groundwater migration and the origin of groundwater.
The Piper plot presented to the right includes three graphs. Each point on a graph
represents one groundwater sample, and the location characterizes the
geochemical composition. The size of the points represents the concentration of
sulfate in the groundwater. Inspection of the major ions data demonstrated that the
smallest points (low sulfate concentrations) were in the youngest water (closest to
grade) while the large points (high sulfate concentrations) were in the oldest water
(deep in the aquifer). While the concept of sulfate gradually dissolving from the
dolomite bedrock seems intuitive, the analysis demonstrated that the concept
worked at the site, allowing sulfate concentrations to used as a tool to assess
hydraulic containment of the groundwater.
The sulfate data demonstrated that the groundwater downgradient of the site
groundwater recovery system was younger than the groundwater within the
containment area of the recovery system. This indicated that the recovery system
was effective. EPA accepted the major ions data as a key line of evidence in
demonstrating hydraulic containment. EPA invited SEI to present the major ions
results at the 2004 USEPA Fractured Rock Conference.
Often overlooked in environmental investigations are the conventional major ion
parameters. The major ions, while no contaminants, can be useful in assessing
groundwater migration and the origin of groundwater.
The Piper plot presented to the right includes three graphs. Each point on a graph
represents one groundwater sample, and the location characterizes the
geochemical composition. The size of the points represents the concentration of
sulfate in the groundwater. Inspection of the major ions data demonstrated that the
smallest points (low sulfate concentrations) were in the youngest water (closest to
grade) while the large points (high sulfate concentrations) were in the oldest water
(deep in the aquifer). While the concept of sulfate gradually dissolving from the
dolomite bedrock seems intuitive, the analysis demonstrated that the concept
worked at the site, allowing sulfate concentrations to used as a tool to assess
hydraulic containment of the groundwater.
The sulfate data demonstrated that the groundwater downgradient of the site
groundwater recovery system was younger than the groundwater within the
containment area of the recovery system. This indicated that the recovery system
was effective. EPA accepted the major ions data as a key line of evidence in
demonstrating hydraulic containment. EPA invited SEI to present the major ions
results at the 2004 USEPA Fractured Rock Conference.
Visualization of Contaminant Data
The objective of every presentation is to get the point
across as accurately and efficiently as possible. This
visualization shows the bottom of the water table aquifer
and all of the wells at the site. The well screen intervals
are color coded, and the diameter of the "screen" is
proportional to concentration. Thus, one can quickly see
all of the data, and spatially, where concentrations are high
and low.
The objective of every presentation is to get the point
across as accurately and efficiently as possible. This
visualization shows the bottom of the water table aquifer
and all of the wells at the site. The well screen intervals
are color coded, and the diameter of the "screen" is
proportional to concentration. Thus, one can quickly see
all of the data, and spatially, where concentrations are high
and low.
Borehole Logging
Borehole video logs are the only way to visualize the
conditions within a groundwater well. These video
captures show a single borehole. The vertical depth
of view (what you can see of the borehole), is about
one foot long. The vertical "stripe" in the right photo
is a measuring tape. The tape was color coded to
accurately determine depths. Borehole logging
equipment often includes a digital readout of depth.
Our experience suggests that the readouts may be
in error by several feet. Thus, where accurate depth
measurements are critical, a tape measure is
recommended.
Borehole video logs are the only way to visualize the
conditions within a groundwater well. These video
captures show a single borehole. The vertical depth
of view (what you can see of the borehole), is about
one foot long. The vertical "stripe" in the right photo
is a measuring tape. The tape was color coded to
accurately determine depths. Borehole logging
equipment often includes a digital readout of depth.
Our experience suggests that the readouts may be
in error by several feet. Thus, where accurate depth
measurements are critical, a tape measure is
recommended.
Photo shows a large fracture in the borehole.
This fracture yields a large volume of water. The
camera is underwater and there are particles
suspended in the water. Occasionally the floating
particles will flow into or out of a fracture.
This fracture yields a large volume of water. The
camera is underwater and there are particles
suspended in the water. Occasionally the floating
particles will flow into or out of a fracture.
Animations
Animations are a format familiar with most audiences.
When completed properly, animations are both informative
and attention holding. The animation to the right presents
site geology by sequentally removing geologic layers, and
then rebuilding the model. This model can be rotated,
flipped, or whatever is an appropriate presentation for the
audience.
Animations are a format familiar with most audiences.
When completed properly, animations are both informative
and attention holding. The animation to the right presents
site geology by sequentally removing geologic layers, and
then rebuilding the model. This model can be rotated,
flipped, or whatever is an appropriate presentation for the
audience.
Photo shows the smooth wall of a borehole.
The concentric, circular marks are the result
of the rotary drilling process. This portion of
the borehole shown here yields no water.
The concentric, circular marks are the result
of the rotary drilling process. This portion of
the borehole shown here yields no water.
Groundwater Flow Modeling
Quantitative analysis of groundwater flow and transport is often necessary to
validate the conceptual model, determine downgradient directions, estimate
flow volumes, contaminant mass flux, plume migration and cleanup, and
assess hydraulic capture. SEI modeling begins bottom up, starting simple and
adding complexity as necessary. Our principal modeling tools are the analytic
element groundwater flow model GFLOW2000, and analytical transport tools
such as the Domenico model. These models are simple, cost effective, and
generally satisfy the needs of the project.
The figure to the right depicts groundwater flow to two extraction wells, and from
two injection wells. The groundwater flow paths are shown as dark blue lines.
Only the flow paths entering an extraction well, or leaving an injection well, are
shown. The use of injection wells close to the extraction wells reduces the
pumping rate necessary to contain the groundwater plume. For this project, the
model was used interactively with plant personnel of optimize the locations of
extraction wells based on plant construction constraints, security concerns, and
maintenance issues. The system has been in operation for several years and
significant improvements in downgradient groundwater quality have been
demonstrated.
Quantitative analysis of groundwater flow and transport is often necessary to
validate the conceptual model, determine downgradient directions, estimate
flow volumes, contaminant mass flux, plume migration and cleanup, and
assess hydraulic capture. SEI modeling begins bottom up, starting simple and
adding complexity as necessary. Our principal modeling tools are the analytic
element groundwater flow model GFLOW2000, and analytical transport tools
such as the Domenico model. These models are simple, cost effective, and
generally satisfy the needs of the project.
The figure to the right depicts groundwater flow to two extraction wells, and from
two injection wells. The groundwater flow paths are shown as dark blue lines.
Only the flow paths entering an extraction well, or leaving an injection well, are
shown. The use of injection wells close to the extraction wells reduces the
pumping rate necessary to contain the groundwater plume. For this project, the
model was used interactively with plant personnel of optimize the locations of
extraction wells based on plant construction constraints, security concerns, and
maintenance issues. The system has been in operation for several years and
significant improvements in downgradient groundwater quality have been
demonstrated.
Groundwater Transport Modeling
The figure to the right presents the results of an analytical transport model.
There were no off-site wells for this project. Contamination was discovered
on-site and investigations were performed only within the property boundaries.
A hydraulic containment system was installed at the downgradient edge of the
site. The containment system was optimized to ensure containment. In 2007,
a Natural Resources Damages suit was brought against the property owner.
An estimate of the off-site areal extent and lifetime of the plume was required
for the calculation of damages. Since no off-site investigation had been
performed, the only way of estimating the plume was to use a transport model.
Using the analytical Domenico model, SEI estimated the off-site plume area to
a specific regulatory limit. A plume was simulated for every year after the first
discovery of groundwater impacts. The figure shown here depicts the
groundwater plumes simulated for sequential years. The plume ends at 2,400
feet off site where groundwater discharges to a stream. In this simulation, a
groundwater recovery system starts 11 years into the project, allowing the
plume to dissipate.
The figure to the right presents the results of an analytical transport model.
There were no off-site wells for this project. Contamination was discovered
on-site and investigations were performed only within the property boundaries.
A hydraulic containment system was installed at the downgradient edge of the
site. The containment system was optimized to ensure containment. In 2007,
a Natural Resources Damages suit was brought against the property owner.
An estimate of the off-site areal extent and lifetime of the plume was required
for the calculation of damages. Since no off-site investigation had been
performed, the only way of estimating the plume was to use a transport model.
Using the analytical Domenico model, SEI estimated the off-site plume area to
a specific regulatory limit. A plume was simulated for every year after the first
discovery of groundwater impacts. The figure shown here depicts the
groundwater plumes simulated for sequential years. The plume ends at 2,400
feet off site where groundwater discharges to a stream. In this simulation, a
groundwater recovery system starts 11 years into the project, allowing the
plume to dissipate.
