2018-05-11_REVISION - M1977493 ‎(2)‎

• Permit No: M1977493
• IBM Index Class Name: REVISION
• Doc Date: 5/11/2018
• Doc Name: Adequacy Review Response
• From: Climax Molybdenum
• To: DRMS
• Type & Sequence: TR27
• Email Name: ECS
• Email Name: WHE
• Media Type: D
• Archive: No

Water Quality Monitoring Plan Climax Molybdenum Company
Version R4 Permit No. M-1977-493
6.3.2 Additional Data Evaluation
This section applies to data collected from all of the monitoring locations identified in Section 6.1, including
the POC well above Eagle Park Reservoir (EV-MW-004). Any additional water quality data from the
established monitoring locations or other locations within Eagle Park Reservoir collected by the Eagle Park
Reservoir Company and provided to Climax, will also be included in the data evaluation.
6.3.2.1 Visual and Statistical Trend Evaluation
Climax will routinely evaluate water quality trends of indicator parameters, and report findings in the Annual
Reclamation Report to DRMS. A copy of these findings will be made available to the reservoir companies.
Evaluation of trends can be complicated by seasonal changes in precipitation and recharge, and by delayed
response to events. It is expected that water quality in the reservoirs will respond quickly to changes in the
quantity and/or quality of runoff water, and respond slowly to changes in the quantity and/or quality of
groundwater. Before long-term changes can be identified, short-term changes (such as seasonal effects)
need to be recognized and considered.
If graphical trends do not suggest declining water quality, no quantitative trend evaluation is needed.
However, a trend that does suggest increasing concentrations in parameters will require a more rigorous
statistical analysis and further actions by Climax to prevent potential impacts to adjacent surface water.
Following a graphical trend analysis that suggests declining water quality, the approach to determining
whether there is a temporal trend will involve the following steps:
1) Based on temporal plots of the parameters of concern, define a window of time for evaluating
whether a trend exists, including the baseline dataset through the most recent sampling period.
2) Develop an approach that corrects for the effects of seasonal variations and that is protective of
adjacent surface waters. In other words, if seasonal peaks occur in concentrations, the evaluation
should be performed to determine if there are trends in the peak concentrations.
3) Compare the most recent 4 sampling results against the 80th percentile upper prediction limit
(UPL), and the most recent 2 sampling results against the 95th percentile UPL. If four consecutive
sample results exceed the 80th percentile UPL, or if two consecutive results exceed the 95th
percentile UPL this fact will be considered along with the other factors in the trend evaluation.
Calculation of the UPLs will be done using the one-sided Student t test equation below:
1
UPL = mean+t[n— 1,1 —a]s 1 + —
n
Where n is the number of samples, s is the standard deviation and a=0.20 for the 80th percentile
and a=0.05 for the 95th percentile.
If a statistical test for a trend is needed, approaches such as Sen's or Mann-Kendall tests (Gibbons, 1994)
will be used, if a sufficient number of samples are available to apply these tests appropriately.
6.3.2.2 Outlier Identification
Outlier results can and do occur in environmental monitoring. Since monitoring of internal sites is being
performed to detect changes in the water quality that may impact uses of Eagle Park Reservoir or Clinton
Reservoir, a careful evaluation of the data will be necessary. The general practice will be to not remove
outliers from the water-quality database, but to consider them in the visual and statistical trend evaluations.
However, Climax will perform outlier testing using Rosner's outlier or other applicable test, considering the
size of the available sample set and validity of the statistical test for the circumstance, and report the results
EPP—Appendix C May 2018 31