REP35632

• Permit No: C1980007
• IBM Index Class Name: Report
• Doc Date: 4/28/1988
• Doc Name: 1987 ANNUAL HYDROLOGY REPORT
• Annual Report Year: 1987
• Permit Index Doc Type: HYDROLOGY REPORT
• Media Type: D
• Archive: No

' Annual Hydrology Report
April 28, 1988
Page 13
1 adjacent to the gal seam can cause localized movement of this water into the
mine workings. To date, groundwater movements of this type have occurred in
' areas of low Dover which are highly fractured (near outcrops and near stream
channels; and where sandstone channels bearing water inrtnediately overlie the
coal seam. Secondly, retreat mining, which causes subsidence, can fracture
' overlying groundwater formations causing movement of the water, usually into the
mine workings.
The permeability of the F seam and overlying strata is very low and the areal
' extent and quantity of water stored in these units is small.
{
The mine workings located near the outcrop, the main portal area, and along
' Sylveste: Gulch behaved similarly to previous years with respect to inflows.
Inflows occurred primarily from the roof in areas of lrn~ overburden and near the
F seam outcrop. Inflow locations are essentially the same as previous years and
are shown on Exhibit II. The estimated flows at these locations are also shown
on Exhibit II for low flow conditions as well a~.spring runoff conditions.
Table 1.4-3 shows total estimated sustained mine inflows for the 1987 water
year.
' The seasonal pattern of mine inflows observed in the mine working at the main
portal area and along Sylvester Gulch indicate that the oolluvium, coal, and
bedrock recharge locally. The azea along Sylvester Gulch contains many
naturally occurring fractures. Water moves down slope through the oolluvium and
fracture zones and discharges as springs and seeps. Water inflows appear to be
controlled by precipitation (mostly snowmelt), depth of overburden, location and
' extent of fracture zones and not by the extent of the underground workings.
Increased mine discharges during water year 1987 in the Sylvester Gulch fan area
' can be attributed to a concerted effort by WEL7C to keep the fan entries
dewatered to a lazger extent. This was done to prevent standing water from
interfering with mine ventilation and to try to cut down on floor heave problems
' in the area. It is not likely that mine inflow rates in Sylvester Gulch were
higher in 1987 than in 1986, but that a trade off occurred. The trade off being
that water normally lost through seepage was actively pumped out of the mine.
' Mine water inflows for the 1988 water year in the Sylvester Gulch area and the
main portal area are expected to be similar to those of 1986 and 1987 water
years; however, precipitation could have an impact on inflow rates if there is a
' dramatic change in 1988.
Mine water inflows for other areas of the mine, namely the 1st west Submain,
' Panels 1W2S, 1W35, 1W4S, and the 1st East Submain are related to particular
geologic and topographic features as well as water bearing formations in these
areas. Each area will be discussed in detail.
' 1st West Submain
The 1st West Submain was not actively mined during 1987. Areas previously
' mapped as wet or damp are shown on Exhibit II. This area remained somewhat
damp during 1987, but did not produce any measureable flows. The wet areas
of the 1st West Submain are thought to be associated with sandstone
channels which immediately or closely overlie the gal seam and with
' fracture zones in the Lone Pine Gulch area.