2015-10-06_PERMIT FILE - C1981019A ‎(3)‎

• Permit No: C1981019A
• IBM Index Class Name: Permit File
• Doc Date: 10/6/2015
• Doc Name: Performance Standards
• Section_Exhibit Name: Volume 15 Rule 4
• Media Type: D
• Archive: Yes

RULE 4 PERFORMANCE STANDARDS
11. A-8 - Located in the West Fork of Good Spring Creek alluvium, this site represents the condition
up -gradient of South Taylor mining activities.
For the alluvial groundwater wells, water levels and field water -quality parameters (Temperature,
Water Level, pH and Conductivity) will be measured quarterly, samples for laboratory analysis
will be collected annually during the second quarter utilizing the paramaters listed below.
Annual Groundwater Laboratory Parameters
pH
Conductivity at 25°C
Total Dissolved Bicarbonate (HCO3 -)D
Solids
Calcium (Ca 1-2)D
Magnesium (Mg+z)D
Ammonia (NH3)
Nitrate Phosphate (PO4 as P)
Sodium (Na+)
Sulfate (SO4)
Arsenic (As)
Iron (Fe)D Lead (Pb)u
Manganese (Mn)
Mercury (Hg)
Selenium (Se)-ra
Zinc (Zn) 117
D = Dissolved
TD = Total Dissolved
T = Total
TR = Total Recoverable
Prior to mining at Lower Wilson, the following three alluvial groundwater monitoring sites will
be added to the sampling schedule:
1. MW -95-01 — Located in the Wilson Creek alluvium, this site represents the upstream,
undisturbed background conditions of the alluvial aquifer.
2. MW -05-03 — Located in the Wilson Creek and unnamed drainage alluvium, this site
represents alluvial groundwater quality immediately downgradient from Lower
Wilson.
3. MW -95-02 — Located in the Wilson Creek alluvium, this site represents the
downgradient conditions below Lower Wilson and the proposed haul road.
Groundwater, Fill Piezometers - The West Pit Fill piezometer will be monitored quarterly for
water levels. After mining, two additional piezometers will be installed into the toes of East
Taylor Fill and West Taylor Fill as described in Exhibit 21 Item 1. These piezometers will be
added to the monitoring program.
A future spoil water monitoring well will be drilled (and water quality monitored) as identified on
Map 41 B in the reclaimed Collom Lite Pit area to monitor and measure the potential development
of a spoil aquifer. This location represents the lowest point in the proposed Collom Lite Pit.
Colowyo has also agreed to monitor well C-04-16 to collect information on potential impacts to
bedrock groundwater quantity and quality prior to, during and post mining activities in the
Collom Expansion Area. The monitoring frequency and parameters captured will mirror those
established for the monitoring of alluvial groundwater wells.
Points of Compliance -
PO/NTS OF COMPLIANCE - WATER MONITORING, RIO TINTO COLOWYO MINE
MEEKER, COLORADO
Prepared by Brant A. Dennis, C.P. G.
March 2009
Collcm — Rule 4; Page 16 Revision Date: 9/28/11
Revision leo.: PR -03