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Beauheim 1987 - Waste Isolation Pilot Plant - U.S. Department of ...

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Thus, at three <strong>of</strong> the four locations where data have<br />

been collected on both Magenta and Forty-niner<br />

hydraulic heads, vertical hydraulic gradients are<br />

upward from the Magenta to the Forty-niner. Data<br />

from the fourth location, DOE-2, are too ambiguous<br />

to allow definition <strong>of</strong> the gradient. These<br />

observations imply that, at least at H-3, H-14, and H-<br />

16, precipitation cannot be infiltrating through the<br />

Dewey Lake Red Beds and other formations<br />

overlying the Rustler and recharging the Rustler<br />

below the Forty-niner. Furthermore, unless and until<br />

a water table is detected in the lower Dewey Lake<br />

and its hydraulic head is measured, the possibility <strong>of</strong><br />

recharge from the surface reaching even the Fortyniner<br />

cannot be evaluated. Efforts are currently<br />

undeway to determine whether or not a water table<br />

exists in the Dewey Lake at H-3 and H-16, but<br />

resolution <strong>of</strong> the question may take several years.<br />

In summary, a more complete understanding <strong>of</strong><br />

vertical hydraulic-head relations among the Rustler<br />

members is available today than existed in 1983.<br />

Data from the WlPP underground facility (Peterson et<br />

al., <strong>1987</strong>) and H-16 indicate a potential for an upward<br />

gradient from the Salado to the lower Rustler. Data<br />

from Mercer (1983) and from H-16 indicate that<br />

upward hydraulic gradients exist between the<br />

unnamed lower member <strong>of</strong> the Rustler and the<br />

Culebra over much <strong>of</strong> the WlPP site. Attempts to<br />

collect representative data on the formation pressure<br />

<strong>of</strong> the Tamarisk have failed to date, but recent data<br />

from DOE-2, H-14, and H-16 support Mercer’s<br />

observation <strong>of</strong> downward hydraulic gradients from<br />

the Magenta to the Culebra at the WlPP site.<br />

Together these observations imply that the Culebra,<br />

the most transmissive member <strong>of</strong> the Rustler, acts as<br />

a drain on the overlying and underlying Rustler. The<br />

data from H-3, H-14, and probably H-16 indicate that<br />

the present hydraulic gradient between the Fortyniner<br />

and the Magenta is upward at those locations,<br />

effectively preventing modern precipitation at the<br />

surface from recharging the Magenta or deeper<br />

Rustler members. Figure 6-3 illustrates these<br />

relationships.<br />

E<br />

G E W<br />

cwm<br />

DEWEY LAKE RED BEDS<br />

ANHYDRITWGYPSUM ?<br />

CLAYSTONE<br />

ANHYDRITE/GYPSUM<br />

MAGENTA DOLOMITE MEMBER<br />

2 I I<br />

.?<br />

I<br />

A<br />

CLAYSTONE<br />

ANHYDRITEIGYPSUM ?I I<br />

0<br />

U<br />

a CULEBRA DOLOMITE MEMBER I J.<br />

CLAYSTONE. HALITE, GYPSUM<br />

LEGEND:<br />

DIRECTION OF HYDRAULIC GRADIENT<br />

BETWEEN TWO WATER-BEARING UNITS<br />

SILTSTONE<br />

SALAD0 FORMATION<br />

+<br />

?<br />

UNKNOWN DIRECTION OF HYDRAULIC GRADIENT<br />

BECAUSE OF UNKNOWN HEAD IN UNIT<br />

Figure 6-3. Vertical Hydraulic-Head Relations Among the Rustler Members at the WlPP Site<br />

137

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