PERMFILE121316

• Permit No: C1982056
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Section_Exhibit Name: EXHIBIT 39 MINE INFLOW ESTIMATES
• Media Type: D
• Archive: No

y Getty Task 2 Page 4 bferch 1, 1983
I
(•
the top of the aquifer. Vertical inflow is allowed only is are es where the
initial piezometric head is greater than the top of the aquifer. This
approzimatioa allows the simulation to be performed without requiring
knowledge of the actual head distribution in the Twentymile aquifer. It
should be noted that this approach also assumes that water is not limited in
I the Txentymile aquifer.
Although calibration can be achieved with the inflow model by setting all
values of the TON array to large times, calibration was performed with a model
that does not have inflow calculation capabilities. Since inflows are not
seeded daring calibration, the smaller model can be utilized and faster
ezecntioa is realized and less core memory is required. Daring the inflow
~ calculations, the model checks to see which grids are active mine grids daring
a time step. The piezametric head in active mine grids is set equal to the
bottom elevation of the coal and is held constant during the period is which
mining is active in those grids. Lateral inflow to each active mine grid from
the four neighboring grids is calculated at the end of each time step. The
equation for flow from a neighboring grid to the mine grid is given by:
I•
Q - KaA dl (1)
where Q = lateral inflow,
~ K =average hydraulic conductivity between grids,
a
A =flow area,
I dh = head difference between grids, and
~ dl = distance between grids.
As as example of how equation 1 is utilized consider flow in the s-direction
from grid (J,I-1) to mine grid (J,I). Using variable games consistent with
those utilized by the program sad identified previously, the variables is
Equation 1 can be calculated:

OX(I) + DX (I-1)
K = -----------------
a _ DX(I) _ DX (I-1) _
• FK(J,I) + FK(J,I-1)
dh = lIT(J,I-1) - ]II(J,I)
(2)
(3)