1 - paducah environmental information center

Paducah Site
B.1.2 DESCRiPtiON OF DATA SET
The data set used for this plume map
revision contains groundwater data from two
types of sample locations: monitoring wells
whose· screen mid-point is between elevations
76.2 m (250 ft) and 97.5 m (320 ft) above mean
sea level, and temporary borings in which a
groundwater sample was collected from
between the same two elevations. Only those
wells and borings for which location coordinates,
surface elevations, and screen or sample depths
were available were included in the data set. As
a result data from the following projects are not
included in this interpretation:
• monitoring wells belonging to the
Tennessee Valley Authority's Shawnee
Steam Plant,
• residential water wells within the study
area,
• temporary borings from the WAG 22 RI,
• temporary borings from the Northeast
Plume Interim Remedial Action, and
• temporary borings from the WAG 3 RI.
This information is currently being
gathered and will be included in the next revision
as appropriate.
B.1.3 SELECTION OF DATA POINTS
To identify those wells and borings
which fit the depth criteria, the OREIS database
was queried for all water samples analyzed for
TCE, 99Tc, or beta activity. The sample interval
for each collected sample was converted to
elevation and filtered to exclude those samples
outside the elevations used to define the RGA.
For monitoring wells, the elevation of the midpoint
of the well screen was used as the sample
depth. The samples were then segregated into
lower, middle, and upper RGA intervals, defined
as elevations 76.2 to 89.9 m (250 to 295 ft), 89.9
to 93.0 m (295 to 305 ft), and 93.0 to 97.5 m (305
to 320 ft) above mean sea level, respectively.
The interval for the lower RGA is larger than the
upper or middle so that data from "channels"
identified in various portions of the plant would
be included in the interpretation. Once the
sample points were assigned to one of the three
intervals, base maps for each interval that
showed only those wells and borings that
collected a sample from that interval were
printed.
B.1.4 SELECTION OF GROUNDWATER
DATA
The groundwater data set consists of
TCE concentrations, 99Tc activities, or beta
activities for those data points defined as RGA in
this report. The data were selected from all
groundwater data collected on or before
December 31, 1999, and entered in OREIS by
March 1, 2000. For monitoring well data, time
versus concentration plots were created and
trend lines developed. To normalize the data,
these trend lines were used to determine the
probable concentration of the well as of June 30,
1999. This value was then plotted on the base
maps. For temporary borings, the actual
analytical value was used. For borings with
multiple samples within one interval, the highest
concentration within the interval waS selected
and plotted on the base maps. Data from CY
1999 were given the highest priority, while data
from earlier years were used in trending and
identifying approximate boundaries with the
oldest data being of least value in the
interpretation.
B.1.5 MAPPING OF DATA.
After all data were plotted on the base
maps, the data were hand-contoured. Separate
maps were made for both TCE and 99Tc in the
upper, middle and lower RGA intervals. The
contour intervals for TCE and 99Tc were as
follows:
0-10
Appendix 0