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waste pile volume, respectively), and that samples with visible sulfide material and highest total
sulfur concentrations were selected from each of these lithologies with aim of better
understanding their acid generating and metal release potential. Sulfide sulfur to total sulfur
ratios indicate that a significant sulfur fraction (up to 50%) is tied up in sulfate phases. Additional
static short-term leach tests and kinetic humidity cell tests are currently underway.
Results of total metals analysis on the waste rock samples indicate that the Bull Hill Resource
Area has elevated content of major components calcium, iron, magnesium, manganese,
potassium, and sodium as well as trace metals cobalt, chromium, lithium, nickel, lead, thorium,
vanadium and zinc relative to average bulk crustal concentrations. This is not unexpected for
silica-under saturated, aluminum-poor igneous material. The fact that a constituent is elevated
in waste rock is not necessarily an indicator of elevated release in effluents associated with the
waste rock, rather elevated release is entirely a function of the solubility and availability of the
mineral phases in which these components reside. Actual constituent release will be evaluated
via short-term and humidity cell leach testing.
5.3.4 Pit Lake
It is anticipated that following the cessation of mining, the Mineable Pit will be recharged from
the bedrock aquifer to form a pit lake approximately 250 feet deep at an elevation of 5,840 feet
above mean sea level (amsl). The lake will take about 100 years to reach steady state water
level. Initially, the water quality of the pit lake is expected to be similar to the quality of the
bedrock aquifer currently being sampled in the area of the pit (see Section 5.3.1.4). Appendix A
of the 2011 Hydrology Baseline Data Report (RER, 2012) provides summary water quality data
for the bedrock aquifer wells, and Table 2.5 of the report lists the analytes that exceed water
quality standards. Based on background water quality, aluminum, arsenic, chromium, iron, and
manganese and the radioanalytic parameters gross alpha, gross beta radium 226, radium 228
and radon 222 could continue to exceed Wyoming water quality standards.
The long-term water quality of the Bull Hill pit lake has been estimated by preliminary
evaluations to be circum-neutral yet be in exceedance of the lowest Wyoming water quality
standards for antimony, arsenic, beryllium, chromium, iron, manganese, mercury, nickel, and
radium 226. RER is in the process of developing the protocol for the conduct of a
comprehensive pit lake water quality study.
5.3.5 Water Quality During Seasonal Closures
The Bull Hill mine plan includes year round operations. No seasonal closures or temporary
cessations of operations are planned. However, the following precautions will be taken in winter
months to maintain proper functioning of the facility:
Storage tanks will be installed with sufficient secondary containment capacity to
contain spills (110 percent of tank and piping volume) that may be caused by
freezing.
Water conveyance structures will be constructed with capacity to handle design
storms and snowmelt.
Water piping systems will be freeze-protected with insulation and heat tracing, if
applicable.
The Miller Creek Access Road, the secondary road connecting the PUG entrance at
the guard house to the haul road from the pit to the PUG, the haul road from the pit
to the PUG and the haul road from the pit to the Waste Rock Facility will be
maintained for winter mining access including snow removal (Map 4.2-2). Additional
roads anticipated for access during winter months using tracked snow machines and
snowmobiles include those Forest Service roads identified on Map 4.2-2. These
