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Bohling, Geoffrey C. / A ground penetrating radar study of water table elevation in a portion of Wisconsin's central sand plain
[DNR-050] (1988)

I. Introduction: motivation and objectives,   pp. 1-9 PDF (2.5 MB)

Page 9

GPR surveys were performed. Of the 27 observation wells shown, 21 are
next to roads where surveys were performed and are therefore potential
calibration and verification points for the radar study. It is important to
point out that most of the " observation wells" shown in Figure 2 are
actually the shallowest piezometers in nests of 3 to 5 piezometers screened
at different depths in one place. Sixteen of the 27 shallow piezometers
shown are in fact observation wells, meaning that the water table inter-
sects the screened interval and thus that the water level actually
represents water table elevation. Of the 21 shallow piezometers next to
surveyed roads, 12 are actually observation wells. In the remaining nine,
water stands between 0.5 and 12 feet above the top of the well screen. It
is possible that, due to vertical hydraulic gradients, the water level in
piezometers screened below the water table would stand higher or lower
than the actual water table elevation. In an actual water table reconnais-
sance study using GPR, one in which only a few observation wells or
piezometers exist in the area, very little or no information concerning vert-
ical gradients would be available.
These 27 shallow piezometers will be referred to as observation
wells in this study. Also, the borings for grain size analyses (locations
shown in Figure 2) are given the labels of the piezometers which were
installed in the auger holes from which the borings were taken.

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