PERMFILE66201

• Permit No: C1981008A
• IBM Index Class Name: Permit File
• Doc Date: 11/21/2002
• Section_Exhibit Name: NH2 1996 Section 2.04.7 Hydrology Description
• Media Type: D
• Archive: Yes

for Monitor Wells GW-N8 and GW-N9 on a monthly basis since September, 1979. Monitor Well
GW-NS is located up gradient and adjacent to the mine pit. As a result, a 13 foot drawdown in
static water level occurred prior to 1983. Since mining ceased in late 1983, the static water level
has begun to recover. Both Monitor Wells GW-N8 and GW-N9 show seasonal fluctuations in water
levels as a result of recharge from the ditch irrigation system. There is no evidence of any
discernible responses to precipitation events at these wells. There are no single aquifer
(overburden or Dakota coal) monitor wells completed in the northwest portion of the New Horizon
1 permit area. Consequently, Monitor Wells GW-N8 and GW-N9 have been incorporated and used
in both the overburden and Dakota coal potentiometric surface maps (Maps 2.04.7-2 and 2.04.7-3).
Potentiometric Surfaces
Potentiometric surface maps for the overburden, Dakota coal and underburden aquifers are
presented in Maps 2.04.7-2 and 2.04.7-3, respectively
Overburden. The potentiometric surface map of the overburden is presented on Map 2.04.7-2.
The water level contours were constructed based on the static water level measurements made
in September, 1987 from five overburden monitor wells and two multiple completion (overburden
and Dakota coal) monitor wells. It was necessary to include the two multiple completion monitor
wells (GW-NS and GW-N9) in the overburden potentiometric map because they are the only
monitor wells located in the northwest portion of the permit area. The overburden generally has
the shallowest static water level of the bedrock aquifers that are monitored within the study area,
so the multiple completion monitor wells should be representative of the overburden aquifer water
levels.
Ground water in the overburden aquifer is generally unconflning to only slightly confining. The flow
in the overburden is generally from the northeast to the southwest and is topographically controlled.
Potentiometric contours indicate that there is discharge of ground water along Tuttle and Calamity
Draws. The ridge that separates the two draws is a ground water divide, causing the ground water
to flow from the ridge top toward both Tuttle and Calamity Draws. The primary recharge area is
from the northeast and from vertical leakage from the irrigation ditches and flood irrigation. The
Revised 25 Jul 2002 2.04.7-6