PERMFILE62071

• Permit No: C1982056
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Section_Exhibit Name: Exhibit 35 Backfill Hydrology Evaluation
• Media Type: D
• Archive: No

• Underground mine discharge are currently averaging 102gpm (0.23
cfs) and show little seasonal variation. Typical total dissolved
solids concentrations are about 2500 mg/1. Discharge rates to
Foidel Creek are anticipated to increase over the next few years
to about 300gpm by 1988. Solute concentrations are projected to
remain similar to present conditions. Once the Fish Creek shaft
is completed, which is projected to occur in 1988, most of the
additional inflows will be discharged to Fish Creek. Consequent-
ly, projected worst case flow rate and concentrations of the
underground mine discharge to Foidel Creek are assumed to be
300gpm (0.67 cfs) and 2500 mg/1 respectively.
The projected backfill discharges to Foidel Creek have been
discussed earlier. Solute concentrations of this discharge are
expected to be similar to Pond F Spring water quality in the
order of 4000 mg/1.
The salt load analysis was performed using data from CYCC site 69
which is on Trout Creek downstream from Middle Creek. Data from
this site is assumed to represent conditions before significant
contributions from mine related discharges to Foidel Creek. The
data presented in Table 2 is taken from a report on cumulative
hydrologic impacts in the Twentymile Park Basin performed by
Kaman Tempo for the Office of Surface Mininq (OSM) in 1982. The
• projected increase in solute concentrations in Trout Creek during
low flow periods are based on the worst case assumptions that all
flow in Foidel Creek is from mine-related discharge and that no
flow occurs in Middle Creek upstream from the confluence with
Foidel Creek. The mass balance equations used are:
Ftd = Ftu + Fm + Fb
Ctd = (Ftu Ctu) + (Fm Cm) + (Fb Cb)
(Ftu + Fm + Fb)
Where:
Ftd = Flow rate of
Ftu Flow rate of
Fm = Flow rate of
Fb = Flow rate of
Ctd = concentration
Ctn = concentration
Cm =concentration
Cb = concentration
Trout Creek downstream
Trout Creek upstream
Foidel Creek mine discharges
Foidel Creek backfill discharges
on Trout Creek downstream
on Trout Creek upstream
of Foidel Creek mine discharges
of backfill discharge
The results of the analysis are presented in Table 3. It can be
seen that the contribution of solutes from the backfilled areas
• at the CYCC operations presently accounts for an increase of
about 57 mg/1 in Trout Creek under worst conditions. This
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