While data
in GIS\Key™ can be queried and cross-referenced in many ways,
two reports in particular were the most important to NASA, contour
maps and hydrographs. Contour maps are aerial snapshots of the
contamination plume. Multiple snapshots can demonstrate plume
migration over time. Because GIS\Key™ allowed the NASA team
to select specific chemicals and contour them separately, the
resulting maps isolated the origins of each chemical, including
the patterns of chemical degradation and transformation (i.e.,
from PCE to TCE to DCE to vinyl chloride). Instead of one generic
plume that appeared to originate from all three sites, individual
plumes and plume transformations were revealed.
The other
important reporting method was hydrographs that depicted constituent
concentrations over time at any given well. Contour maps gave
the macro view of changes over a relatively large area, while
hydrographs showed a micro view of changes at individual wells.
Especially revealing was noting the increase in concentrations
of certain chemicals in wells that were upgradient of locations
previously considered source areas.
Of particular
help in managing the data, according to Hogan, was the GIS\Key™
function that automatically flags wells that rise or fall in
concentration after new lab results are input. GIS\Key™ allowed
users to build this standardized query, making it unnecessary
to generate the same query with each new lab transmittal. Each
time new data was entered, GIS\Key™ alerted the user of any
significant changes.
"GIS\Key™
produced tremendous savings in staff time by accelerating our
ability to assess the chemical and lithological environmental
conditions," Hogan emphasized.
A digitized
base map (a U.S.G.S. 7.5-minute quadrangle) inside GIS\Key provided
the foundation for displaying the contour results from the Superfund
sites. Using the AutoCAD interface, GIS\Key™ displayed map symbols
used to represent individual sampling wells. Numeric concentrations
were posted next to each well to give a meaningful picture at
a glance of the contamination status. These isopleth maps can
be output as color meshes showing the same information, but
adding color contours that readily show chemical distribution
or groundwater elevation.
Due to
GIS\Key’s™ integrated design, data need only be entered
once. The same chemical and geologic data used in the site maps
was also available for the constituent vs. time graphs that
gave NASA a picture of the changes in individual wells. The
graphs were simple to prepare. The user selected the time period,
the chemical or chemicals of interest, and the default values
for non-detect concentrations, the reporting limit, one-half
the reporting limit, or zero. The template for the chemical
time series graphs is just one of hundreds in the GIS\Key™ library
of templates designed to visually display data.
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