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

• _ ~ •

points. The baseline quality of thr water in Oak Cn~r~}: i~ •lcnr•r,il.l,l poorer to that
in the portions of Trout Creek, above the permit arch, due to c;ctensivc mining that has
occured along the stream during the past century.
ALLUVIAL VALLEY FLOORS
Two alluvial valley floors (AVF's) exist within tl]e study areas along Trout Creek,
located just [Jest of the permit area, and along Oak Creek, located in a watershed East
of the permit area. Both have en ouch associated unconsolidated deposits and sufficient
water yield to be considered alluvial valley floors.
The deposits along Trout Creek consist of four terraces (Qtl, Qt2, Qt3, Qt4), of which
only two (Qtl and Qt2) are crater hearing. The terraces aru shown on .dap 7.5-2I of the
permit application, which delineates the boundaries of the AVF. 'fhe Qtl terrace,
equivalent to the Trout CreeF: active floodplain, is hudroioyically connected with the
Trout Creeic channel. Since Trout Creeic is a perennial stream, baser"1 ow throughout
the year is maintained by discharge from the Qt1 alluvial ground water. The Qt2 terrace
is also water bearing since it contains a perched a,uifer situated atop bedrock; the
Qt2 terrace, however, is not in direct communication with the Qtl terrace. Discharge
from the Qt2 terrace will eventual., reach Trout Creek via seeps along the .~drock
face which separates the Qt2 terrace from the modern floodplain. Recharge to the Qt2
terrace is From infiltration of 1.oca1 precipitation only, and not from any type of
hydrologic connection with the active Trout Creek floodplain. On the permit area side
of Trout Creek, only the Qtl and nt2 terrace predominates, although the Qt2 terrace
is present on a limited basis.
The applicant calculated the mean annual water yield o.` Trout Creek at a point just
downstream of the mine site as approximately 37,500 acrr_-feet/uea r, in di ca tinq that an
ample supply of water is availai~Je for flood irrigation purposes. Current irrigation
activities do occur within the 'C rout Creek. AVF study area. ,Nap 4.6-16 of the permit
application delineates ditches and flood irrigated land.
A subirrigation potential also e:rists on the ntl terrace of Trout Creek. ,]tap 2.4-1
of the permit application delineates those sr>ecl es or vegetation on the Qt1 terrace
which are indicative of subirrigated conditions. Ground ~.'ater levels obse reed in the
alluvium along Trout CreeY, also support the contrntinn that subirrirration is occuriny.
Depths to water ranging from nne to six feet have been ohs~arved in the monitoring.
The applicant has presented .1 and use information on Exhi;,it 2.9-1 of the permit applica-
tion. Land use along the Trout Creek ADP consists of cropland, pasture, and shrub
and brush rangeland. Irrigated native hog is produced by :;,.venal farmrs .in the vicinity
of the permit area. flay productivity information i:; nresenter7 in Section 2.9.3.2 of
the permit application. The applicant has also assessed the significance of the nay
production on Trout Creek AVF to the individual farming units. This is expressed in
terms of "percent of total hnu production" for each indivldual Farm. This can be found
in s-ection 2.9.3.2 and Exhibit 3.7-1 of ti]c permit application. Information presented
by the applicant indicate that the hay production on the Trout Creek AVF is significant
to the farming units in the vicinity of the nuns.
Oak Creek also has enough associate<? .~llurJ:;m :end aa•ail:able ,.•oter to be consir.]ered an
AVF. As shown on ;dap 2.5-21, Gdo levels of terraces exist. Tha ~]tl terrace is the modern
floodplain; ground water con rained in this terrace is directly connected with Oak Creek.
The Qt2 terrace is generally sparse and does not contain ground water to any significant