GENERAL48922

• Permit No: C1980001
• IBM Index Class Name: General Documents
• Doc Date: 10/29/1981
• Doc Name: Proposed Decision and Findings of Compliance
• Permit Index Doc Type: FINDINGS
• Media Type: D
• Archive: No

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[dater Ilse
Present surface water use in the Trout C'rec{: watershed includes domestic supply,
stock watering and irrigation. In tyre region surrounding the pe,~mit area, thirteen
wells are in use as domestic supplies, seven ditches are used primarily for irrigation,
~-~- while also supplementing domestic and stock water supplies, and ten springs are being
L used for domestic and stock water purposes. Only one adjudicated water right was
/ identified in the Oak Creek watershed adjacent to the mine; a well has been installed
//////~~~~~~ by Pittsburg and hfidway near the office area (p. 2.5-22 and Exhibit 2.5-Z1 of the permit
application).
[Ja ter quantity and nua lity
In addition to stream guantitrl and duality monitorin_ stations installed to _gather data
for this permit application, a previous study of Trout CreeF: (MCtdhorter, et a1., 1979)
had been conducted at the mine site in 1975, and data from that research is available
for delineating baseline stream characteristics. Results from both studies were generally
well-documented. Exhibit 2.5-2 illustrates the monitoring sites established during the
baseline period studies. Seasonal runoff hydrographs constructed from available data
for both streams show peak discharges occurring in April, May and June as a result of
snowmelt. Low flows in both streams begin in the late summer and extend through the
winter months until the sprinn runoff begins.
The average annual runoff from the Trout Creek watershed, including the permit area,
is estimated from previous years of record at 37,500 acre-feet/year (p. 2.5-14 of the
permit application). For 53.25 square m.iL,s, this Yields an average death of 1.1 feet
of direct runoff from the entice ~:~atershed. The acne itself comprises approximately
3975 acres, or twelve percent of the total Trout Cry°eF; watershed. The area to be
affected for the life of the mine yields auprorimatcly 1710 acre-feet of runoff annually
to Trout Creek.
Only a relatively few acres of the permit area drain into Oak Creek. The applicant
extrapolated from recorded da W and, basing the estimate on conditions being similar to
the Trout Creek watershed, calculated that Oal: CreeF: will meld 10,80'0 acre-feet/uear,
or O.o2 feet of run ofF from a dnlinago area of 27.' square miles.
baseline water quality data r:~os gathered at four stream sampling points established
at locations ai;ove and i~elow mining ~~ctivitics on :rout Creek (Exhibit 2.5-2 of the
permit application). ;donthly grab samples taken at the:;e points were analyzed and the
results indicate that concentrations of total dissolved soilds, ions and trace elements
show seasonal fluctuations. [dater quality upstream of the mine site is fair, character-
ized by concentrations of dissolved iron, manganese, nickal, silver and zinc that
occasionally exceed criteria for drinF;.ing :rat%•r quality recomrrrnded by the National
Academies of Science and Engince ring.
Baseline data indicates that runoff from existing Tuned areas has degraded water 7uality
in Trout Creek adjacent to the mine, although water quality irnproves as the stream
leaves the permit area. A further discussion is presented in Section III of this document.
rJa ter quality baseline data r_ol lecter? from two grab sample points in Oak Creek indicate
that little degradation occurs between the upstream and downstream sampling points.
Seasonal variations of constituent concentrations arc consistent bet:reen the two sampling