2016-03-28_HYDROLOGY - M1977493

• Permit No: M1977493
• IBM Index Class Name: Hydrology
• Doc Date: 3/28/2016
• Doc Name: Comments
• From: Climax Molybdenum
• To: DRMS
• Email Name: ECS
• Media Type: D
• Archive: No

Eagle Park Reservoir Chemical Loading and Mixing Analysis
Table 4. Water Oualitv Data for Eagle Park Reservoir - EPR Outlet
EPR Outlet Data Summary
(8/2012 - 9/2014)
Cadmium
Dissolved
(m /L)
Copper
Dissolved
(m /L)
Iron
Dissolved
m l
Lead
Dissolved
m L
Manganese
Dissolved
(m /L)
Molybdenum
Dissolved
m L
Sulfate
Dissolved
m /L)
Zinc
Dissolved
m L
Field pH
su
Number
7
7
7
7
7
7
5
7
7
Number Detected
0
5
0
0
2
7
5
2
7
Minimum
< 0.0001
< 0.0005
< 0.02
< 0.0001
< 0.002
0.030
17
0.003
7.4
Maximum
< 0.0001
0.0007
< 0.03
< 0.0006
0.008
0.050
35
0.010
8.4
Mean concentration
0.0001
0.0006
<0.02
0.0002
0.005
0.040
27
0.008
7.7
Standard Deviation (o)
0.0000
0.0001
<0.00
0.0002
0.002
0.008
7
0.003
0.4
Model Input Values (mean +2o)
1 0.0001 1
0.0008
1 0.029
0.0007 1
0.008
0.056
40
0.015
7.7*
Note: Data reported as notdetected wereevaluated atthemethod detection limitfor statistical summary
*inputvaluefor pH is arithmetic mean value
Mass Balance Mixing
PHREEQC was used to apply a mass balance approach to calculate the loading and mixing of
indicator parameters from groundwater sources and estimate the resulting mixed water quality
in EPR. Results were then compared to Eagle River Segment 14 Surface Water Quality Standards
(WQS).
Depending on the pH and the oxidation/reduction state of the water, mineral phases may
become saturated in solution, resulting in mineral precipitation. Chemical precipitation removes
chemical mass from the water column and establishes a limit on the maximum dissolved
concentrations for the associated components of that mineral. For this reason, the PHREEQC
model was set to allow two primary mineral species, Ferrihydrite (Fe(OH)3(am)) and Gypsum
(CaSO4.2H2O), to precipitate out of solution if the concentrations reached saturation. In
addition, the model was set to allow, or consider, the sorption of metals to ferrihydrite. Under
these conditions the model predicts the reduction of dissolved cadmium, copper, lead and zinc
concentrations through sorption.
The calculated loading from groundwater, with all indicator parameter concentrations equal to
the proposed NPLs (Table 3), was mixed with a limited reservoir volume of 1,077 acre-feet with
initial EPR water quality based on data from the EPR Outlet (Table 4). This represents a
conservative condition where the flux of the groundwater would only mix with water above the
gravity outlet (approximately coincident with the elevation of the thermocline as identified in
recent EPR water quality evaluation reports (LRE, 2014).
Climax Molybdenum Company Page - 5 -