PERMFILE64785

• Permit No: C1980001A
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Doc Name: pages 2.5-1 to 2.5-107
• Section_Exhibit Name: 2.5 HYDROLOGY
• Media Type: D
• Archive: Yes

i~
in this document. In addition, data available from previous studies are utilized where
appropriate.
General Water Duality -Four stream sampling points were established
on Trout Creek and designated as TRA through TRD. Grab samples were Taken
monthly. The locations of these stations are shown on Exhibit 2.5-2, and complete
data sets are in Section 2.5.5 entitled "Compilation of Field Data." The variation
of water quality as characterized by the common parameters pH, total dissolved
solids, bicarbonate, sulfate, magnesium, calcium and sodium is shown for each of the
four stations in Exhibits 2.5-12a, 2.5-12b, 2.5-12c and 2.5-12d. These plots show that
the quality of Trout Creek waters degrades with increasing distance downstream
from station TRA. Most of this degradation is believed to result from drainage from
the current mine as explained below. It is observed That most of the parameters
shown on this exhibit attain the greatest concentration in the late fall when the
stream is at base flow conditions and in April, when snowmelt is occurring between
TRA and TRD but before significant spring runoff above TRA has started.
Data collected in a previous study at a location immediately upstream from
TRB show The seasonal relationship between runoff and water quality (as char-
acterized by TDS), also. This relationship is shown in Exhibit 2.5-4, where the
concentration of total dissolved solids is superimposed upon the seasonal runoff
hydrograph. Of particular interest is the observation that the peak TDS occurs in
the early spring. This is caused by pickup of dissolved solids by the spring runoff
from the portion of the watershed in which the existing Edna Mine is located. The
discharge of this runoff is small relative to that of Trout Creek so a large increase
in the Trout Creek discharge is not observed. On the other hand, the dissolved solids
concentration in this runoff is much greater than that in the Trout Creek waters
originating above TRA. In May, the runoff from the upper reaches of Trout Creek
begins in earnest and is sufficient To dilute the small quantity of runoff from the
lower part of the watershed. This explanation of the TDS-discharge relation shown
in Exhibit 2.5-4 is substantiated by measured concentration-discharge relationships
from selected areas within The existing mined area and ai the T R-a gaging station
(McWhorter, et al., 1979). Further discussion of reasons for the existing degradation
of water quality is contained in Section 2.5.3.2.
The data shown in Exhibits 2.5-12b through 2.5-12d show the above
phenomenon, although in less detail since only monthly samples were collected. For
example, the peak TDS concentrations in April shown on Exhibit 2.5-126 for stations
TRB, TRC and TRD are caused by inflow from the mine area before high runoff has
Revised 7-81
2.5-23