2007-11-01_PERMIT FILE - C1982056A ‎(4)‎

• Permit No: C1982056A
• IBM Index Class Name: Permit File
• Doc Date: 11/1/2007
• Section_Exhibit Name: 2.06 Special Categories of Mining
• Media Type: D
• Archive: Yes

• basin wide average is behveen IS and 20 percent (meaning that ly and 20 percent is consumptively used).
Since the highest yearly irrigation consumptive use value measured in [he Trout Creek basin is 21.92
inches of water, ct can be calculated that bet+veen 109.6 and 146.1 inches of irrigation water are actually
applied. Since virtually none of the irrigation systems evaluated in connection with [his penni[ revision
application have SCS Ranch Management plans, have never (as far as records show) obtained professional
assistance from either [he SCS or Colorado State University Extension Office, and given the relatively
high level of inactivity of these irrigation systems, it is safe to assume that the probable application
efficiencies of these systems is less than that of [he basin wide average. Nevertheless, TCC believes that
[o be consistent with the "+vorst case" scenario utilized by the CMLRD, i[ must be concluded that the
irrigational systems equal the highest basin wide average of 20 percent application efficiency.
l'he 109.6 inches of water applied at [he 20 percent application efficiency exceeds the probable depth of
irrigation requirement for Fish Creek, calculated [o equal 56.2 inches. It also exceeds [he 37.2 inch
value for Trout Creek below Foidel Creek. From this comparison i[ can easily be concluded [hat sufficient
leaching is built into the existing inefficient irrigation systems to supply behveen 195 and 295 percent of
the water necessary [o maintain the electrical conductivity of the drainage water and soil profile below the
2.0 mmhos/cm threshold in a long-term steady state condition.
fhe SCS and CDWR offices in Steamboat both report that the typical period of irrigation normally runs
from approximately June 1 to the end of August. Typically, Flows are higher during this period as
compared [o the period specified by CMLRD in the current evaluation. It can be concluded that actual
irrigation water quality used is substantially better than that utilized in the current evaluation.
Aside from the overall impact of salinization associated with utilizing irrigation waters of increased
• electrical conductivity, dte next most common salinity hazard is that associated with a potential sodium
hazard. Handbook No. 60 (page 80) presents a diagram evaluating irrigation waters with respect to
potential sodium hazard. In order to evaluate this potential, TCC conducted an evaluation of the potential
sodium hazard based upon projected low t7ow conditions experienced during dte months of August
through September when flow is lowest and water quality [he most potentially limiting. This evaluation is
described in more detail in Rule 2.05.6(3)(b)(iv), Probable Hydrologic Consequences. The specific
numbers produced in this evaluation are presented in Table 63, Predicted SAR Conditions During Low
Flow Periods for Fish Creek and Trout Creek. The resulting sodium hazard, as measured by the sodium
adsorption ratio (SAR) for the three points previously evaluated in this site specific evaluation, resulted in
average SAR values of 2.08 for Fish Creek below the mine discharge waters entering the stream, 0.88 for
Trout Creek a[ [he point where mine discharge waters from the Foidel Creek drainage may firs[ be utilized
for irrigation, and 0.39 for that segment along Trout Creek where the affected waters from both the Fish
Creek and Foidel Creek drainage waters may affect the receiving stream.
According to the salinity classification diagram in Handbook No. 60, the above SAR values constitute an
insignificant sodium hazard. Handbook No. 60 reports that such low sodium waters "can be used for
irrigation on almost all soils with little danger of the development of harmful levels of exchangeable
sodium". Given this evaluation, there is no evidence to suggest [hat utilization of waters affected by mine
discharge will have any adverse sodium impact. The time period specified by the CMLRD, although it
might correspond with the portion of [he +vater year wherein water quality is most limiting, can not
reasonably be used [o predict potential impacts. During the majoriq~ of this period, freezing conditions are
experienced, thus limiting or eliminating evapotranspiration. Just as color infrared photography taken in
September oP 1978 was rejected by OSM in their technical analysis of permit 79-177 as not being indicative
. of documenting evapotranspiration due [o probable killing frosts, [he assumption suggested to be used in
the current evaluation can be rejected. Using the CDWR consumptive use data for the years 1983 through
195 and comparing the monthly use values against the highest recorded yearly consumptive use value
N1R 97-I i4 2.06-19 Re+•ised 9/10/97