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

begun above TRA. Notice that station TRA does not exhibit a peak TDS value in
April. It will also b oticed that water quality tends to improve between stations
TR-C and TR-D. The reason for this improvement is believed To be the locations
of the stations relative to The presently disturbed area and The relative quality of
_ waters entering Trout Creek above TR-C and between TR-C and TR-D. Specifically,
the water quality at TR-C reflects I. the very good qualify waters entering the
stream above TR-A and 2. the waters of reduced quality that enter the stream
between TR-A and TR-C from the mined lands. The water quality observed at TR-
D reflects both of these components but, in addition, is affected by waters that enter
the stream between TR-C and TR-D. The quality of these waters is relatively high
because they derive from undisturbed lands. Thus, there is a tendency for stream
waters of TR-C to be diluted by inflows below TR-C and the water quality improves

The locations of the two stream sampling points on Oak Creek are shown on
Exhibit 2.5-2 (OK-A and OK-B). The variation of selected water quality parameters
over the period of record is depicted in Exhibits 2.5-13a, 2.5-13b, 2.5-13c and 2.5-
13d. Very little difference between the concentrations aT the upstream and
downstream stations are observed. The water quality data shows a marked decrease
in The concentration of most parameters in May when runoff is near the peak. Also
of interest is the observation that concentrations did not peak in April on Oak Creek
as they did on the three downstream stations on Trout Creek. This is because the
inflow between OKA and OKB during May is not carrying high concentrations of
dissolved solids as is the case for runoff from the mined land.
Exhibits 2.5-12a through 2.5-12d and 2.5-13a through 2.5-13d represent one
method of summarizing a great deal of data in a manner that permits the salient
features to be identified. In addition to these graphical summaries, Tables 2.5-8a,
2.5-Sb and 2.5-9 contain a limited statistical summary of the data collected at the
four stations on Trout Creek and the two stations on Oak Creek. In those tables (n)
is the number of samples, (x) is the arithmetic mean, and ( a) is the standard
deviation. The number of determinations is not the same for all parameters for a
variety of reasons. At times the field pH meter failed, the laboratory didn't report
a value, insufficient sample, etc. No outliers were edited from the data sets in the
preparation of these summaries. However, in those cases where a particular
determination was apparently an outlier, the mean value was computed both with and
without the apparent outlier (e.g, total suspended solids at TRA in Table 2.5-Sa).
The raw data from which these summaries were prepared are contained in the section
entitled, "Compilation of Field Data," Section 2.5.5.
Revised 7-81
2.5-28