_REPORT - C1980007

• Permit No: C1980007
• IBM Index Class Name: Report
• Doc Name: ANNUAL HYDROLOGY REPORT MT GUNNISON NO 1 MINE WATER YEAR 1989
• Annual Report Year: 1989
• Permit Index Doc Type: Hydrology Report
• Media Type: D
• Archive: No

HYDROLOGIC DATA INTERPRETATION AND
IMPACT ASSESSMENT FOR THE PERMIT AREA
AND ADJACENT AREAS
This section focuses on three areas.First,it analyz- Gulch behaved similarly to previous years,relative
es the hydrologic data gathered during water year to inflows. Inflows occurred primarily from the
1989. Second, it assesses impacts of mining on the roof in areas of low overburden and near the "F'
quality and quantity of water in surface streams, seam outcrop. Inflow locations were essentially the
springs, groundwater aquifers, mine inflows, and same as previous years and are shown on Exhib-
mine discharges during water year 1989. lastly, it it 11. The estimated flows at these locations are
estimates potential impacts of mining on these also shown on Exhibit 11. Separate estimates are
waters during water year 1990. provided for low flow conditions and spring runoff
conditions.Table 6 shows total estimated sustained
Surface water,springs,and groundwater are consid- mine inflows for the 1989 water year.
ered separately even though they are interrelated.
The report attempts to show the interrelationships The seasonal pattern of mine inflows observed at
that are significant or could be expected. Because the main portal area and along Sylvester Gulch
mine water and groundwater are so interrelated, indicate that the colluvium, coal, and bedrock
they are discussed together. recharge locally. The area along Sylvester Gulch
contains many naturally occurring fractures. Water
ASSESSMENT OF MINE moves down slope through the colluvium and
fracture zones and discharges as springs and seeps.
WATER AND Water inflows appear to be controlled by the
GROUNDWATER amount of precipitation (mostly snowmelt),depth
of overburden, and location and extent of fracture
zones and not by the extent of the underground
MINE WATER workings.
The underground room and pillar mining methods Mine water inflows for the 1990 water year in the
in use at the Mi. Gunnison No. 1 Mine can affect Sylvester Gulch and the main portal areas are
groundwater in essentially two ways. First, devel- expected to be similar to those of the 1988 and
opment mining in areas where groundwater is 1989 water years. However, precipitation could
present in or near the coal seam can cause local- have an impact on inflow rates if there is a dramat-
ized movement of this water into the mine work- is change in 1990. Precipitation during 1989 was
ings. To date,groundwater movements of this type less than 1988.
have occurred in areas of low cover which are
highly fractured (near outcrops and near stream Mine water inflows for other areas of the mine are
channels) and where sandstone channels bearing related to particular geologic and topographic
water immediately overlie the coal seam.Secondly, features as well as water-bearing formations.These
retreat mining can cause. subsidence and the areas include the 1st West Submain, Panels 1W1S,
fracturing of overlying groundwater formations. 1W2S, 1W3S, 1W4S, 1W5S, 1W6S, the Ist East
Again, water usually moves into the mine work- Submain,and the Northwest Submains. Because of
ings. At the Mi. Gunnison No. 1 Mine,the perme- these local features, each area is discussed sepa-
ability of the "F"seam and overlying strata is very rately.
low and the areal extent and quantity of water
stored in these units are small. 1st West Submain
During 1989, the mine workings located near the The 1st West Submain was advanced two crosscuts
. outcrop, the main portal area, and along Sylvester during 1989 to make room for the 1 W6S panel.
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