PERMFILE57005

• Permit No: C1980005A
• IBM Index Class Name: Permit File
• Doc Date: 5/20/2005
• Section_Exhibit Name: Tab 7 Hydrology
• Media Type: D
• Archive: Yes

State Reg.
II. SURFACE WATER INFORMATION •
As illustrated on Exhibit 7-3, the Seneca II Mine lies within the drainages
of Little Grassy Creek, Grassy Creek, and two unnamed tributaries of
Fish Creek. These drainages are part of the Yampa River System which
in turn lies in the Upper Colorado River Basin. Seneca Coals, Ltd. has
obtained baseline information in terms of quantity and quality on the
Yampa River and Fish Creek (upstream and downstream from mining)
from government agencies. In addition, Seneca Coals, Ltd. has estab-
lished abaseline monitoring program on the drainages that are in the
direct vicinity of the mine. The following discussion gives quantity and
quality information for each of these basins and relates this information
to effluent from the mine.
A. Yampa River Basin
Like other rivers in the Upper Colorado River Basin whose source lies
along the Continental Divide, snowmelt is the principle source of water
for the Yampa River and most of its tributaries. According to lorns et
al. (1965), summer precipitation has little effect on the discharge of
principal streams. The base flow of the streams draining the high moun-
tain areas is uniform for nine months of each year with April, May, and
June showing substantially higher flows. The streams draining the areas
of lower altitudes in the central and western part of the basin are pri-
marly intermittent.
Figure 7-6 shows a typical hydrograph for the Yampa River near the
mountains at Steamboat Springs. High flows between 200 and 1,500 cfs
occur between the beginning of April and the end of June. Further
downstream east of Hayden near the discharge of Grassy Creek peak
flow also occurs during the spring. This is illustrated in Figure 7-7 for
the 1979 water year. As expected, there is more flow at the Hoyden
station.
Seasonal variation in water quality also occurs. During months of high •
water in the spring and early summer, the concentrations of total dis -
7-54
Revised 5/27/81