Beal EECA_Revision 6_final.pdf

ENGINEERING EVALUATION / COST ANALYSIS

United States Department of Agriculture Forest Service

Northern Region

ADSU

FINAL

(Revision 6)

Beal Mountain Mine

Beaverhead-Deerlodge National Forest Silver Bow County, Montana

March 2010

FINAL

ENGINEERING EVALUATION / COST ANALYSIS

BEAL MOUNTAIN MINE

BEAVERHEAD-DEERLODGE NATIONAL FOREST

Prepared For:

USDA Forest Service Northern Region

Missoula, Montana

Prepared By:

Tetra Tech, Inc.

851 Bridger Drive, Suite 6 Bozeman, Montana 59715

March 2010

Final Beal Mountain Mine EECA - USDA Forest Service, Northern Region ES-i

Tetra Tech March 2010

EXECUTIVE SUMMARY

The Beal Mountain Mine is located in the headwaters of German Gulch in the Pioneer Mountains, Silver Bow County, Montana, about 16 miles west southwest of Butte and 10 miles southwest of Fairmont (Gregson) Hot Springs. The mine is primarily situated on land managed or controlled by the United States Department of Agriculture, Forest Service (USDA-FS), Beaverhead-Deerlodge National Forest (B-DNF). The Beal Mountain Mine completed open pit mining operations in 1997 and gold recovery from the heap leach pad in 1999, with reclamation of the mine disturbances continuing through 2003. With a filing of bankruptcy in 1998, and exhaustion of bonding funds to complete reclamation, the USDA-FS became the lead agency responsible for final mine closure.

The USDA-FS placed the mine closure under its CERCLA (Comprehensive Environmental Responsibility, Compensation, and Liability Act) authority, and determined that the non-time-critical removal action process would be followed for mine closure. As part of that process, the USDA-FS contracted with Maxim Technologies, Inc. (Maxim was acquired by Tetra Tech Inc. in 2005) to develop a report documenting existing conditions at the Beal Mountain Mine Site (Maxim, 2004a). This document was followed by a draft Engineering Evaluation/Cost Analysis (EE/CA) (Maxim 2005) that evaluated closure options for the Beal Mountain Mine.

In February of 2009, the USDA-FS contracted with Tetra Tech, Inc. (Tetra Tech) to revise and update the 2005 Draft EE/CA (Maxim 2005) to a final document. The 2005 Draft EE/CA needed to be revised to incorporate water quality monitoring and other data that had been collected to fill data gaps since the release of the 2005 document. This new data as well as a description of activities that have taken place at the Beal Mountain Mine site since 2005 were incorporated into a Public Draft Beal Mountain Mine EE/CA (Tetra Tech 2009) that went out for public review and comment. These comments and additional revisions by the Agencies involved have been used in the preparation of this Final EECA for the Beal Mountain Mine site. A response to public comment section has been included as Appendix F of this report.

Working with the Forest Service, Tetra Tech, Inc. developed and revised the 2005 EE/CA to evaluate final closure options for the Beal Mountain Mine. The purpose of this document is to present an evaluation of alternatives that address issues at the mine that constitute the release or threat of a release of contaminants present at the site. The objective of this EE/CA is to screen, develop, and evaluate potential removal alternatives that could be used to mitigate environmental issues identified at the site.

The USDA-FS goal for the site is to close the mine and allow the area to return to its pre-mining multiple use state. Although a large portion of the mine property is reclaimed, several on-going operational, maintenance, and reclamation requirements need to be met for specific facilities before final closure is complete. There are also outstanding issues that potentially affect the environment that need to be addressed. These issues include the long-term geochemical reactivity of mine wastes (including both acidity and the release of selenium to the environment from several potential mine sources), geotechnical stability of the pit high wall and leach pad dike, infiltration of precipitation and groundwater into the leach pad, and treatment and disposal of excess solution accumulating on the heap leach pad.

ES-ii Executive Summary

Final Beal Mountain Mine EECA

ISSUES RELATED TO EXISTING CONDITIONS OF MINE FACILITIES

Pit Wall and Leach Pad Stability

There are currently two active slides in the Beal Mountain pit area, the west wall and the clay/sill slide. The west wall slide has moved across and into the Beal Mountain pit in an eastward direction. During active mining, movement of this slide was reported in the range of 10 to as much as 100 feet per year. Based on analysis of projected slide configurations, it is projected that the west wall slide may move as much as another 200 feet before movement ceases (Sitka 1997).

The clay/sill slide is a relatively small slide located immediately south of the southern corner of the heap leach pad. During mining, the southern corner of the leach pad containment dike experienced some geotechnical instability due to movement of the clay/sill slide. There were several responses implemented to mitigate the clay/sill slide’s movement during mining and closure activities including installing and operating dewatering wells to reduce pore pressure on the slide plane. Dewatering was discontinued in July 2003, but reinstated by the US Forest Service in the spring of 2008. By May 2005, however, with water levels in the dewatering wells at their seasonal high, two inclinometers located in the area of the clay/sill slide showed movement at depth. Movement at depth was previously seen in both of these inclinometers during active mining in the mid to late 1990’s. The inclinometer casings were resurveyed again in the spring of 2008, and one of the two wells showed ½” movement since the 2005-surveying event. In May of 2008, and in June and October of 2009 TetraTech performed three additional inclinometer hole surveys of casings in the vicinity of the clay-sill slide area. Cumulative displacement on a previously identified shear plane at 165 feet in S195-3 has been 2.75 inches since the installation of casing S195-3 in 1995. The steady increase in the cumulative displacement observed indicates there is active on-going movement at a depth of 165 feet below the top of the casing on the clay-sill slide block. No significant recent displacement is apparent in hole S197-1. No significant recent displacement was noted in casing S197-2;

however, historical displacement in 2005 has occurred at elevations of 70 and 270 feet below the top of the casing.

Three survey prisms installed in 2005 in the clay sill slide area had shown no significant displacement through 2008. In 2008, ten additional survey prisms were installed near the clay-sill and west wall slide areas. Survey prism was re-measured in July and October of 2009.

Movement in the west wall slide area over this period of time as measured in nine prisms, ranged from to as little as 0.107 feet, to as much as 0.36 feet, with movement occurring to the east and southeast (toward the pit high-wall). Movement in the clay sill slide area over this same period of time ranged from as little as 0.096 feet to as much as 0.138 feet to the south.

Displacement measurements in inclinometer casings and between survey prisms located in the west wall and clay sill slide masses indicates progressive down-slope movement at an increasing rate.

Slope stability analyses indicate that the crest of the leach pad dike has a relatively low factor of safety under worst-case conditions and regression of the clay/sill slide uphill into the leach pad dike could occur. If this occurred, spent ore and pad solution may be at risk for uncontrolled release to the environment.

Final Beal Mountain Mine EECA - USDA Forest Service, Northern Region ES-iii

Waste Rock

Waste rock was generated from mining of both the Beal Mountain pit and the South Beal pit.

Most of the rock placed in the waste rock dump was mined from the Beal Mountain pit. These wastes were also used in the construction of the leach pad containment dike and haul roads. A significant portion of waste rock (35% to 65%) mined from the Beal Mountain pit presents a risk of acid generation and subsequent acid rock drainage.

Waste rock seepage currently contains elevated concentrations of selenium that originates from several different sources within the waste rock dump. These concentrations are manifested in seepage water emanating from spring SPR-10A (buried under the upper end of the waste), spring SPR-5 (at the toe of the waste rock dump), and water from the toe drain collection system. This combined seepage is currently collected in pipeline system originally constructed for waste rock seepage disposal under an old MPDES permit during active mining operations and during the initial stages of mine closure. This pipeline system currently discharges into a series of five infiltration galleries located in alluvial material along German Gulch below surface water sampling station STA-3A.

Leach Pad Solution Volume and Geochemistry

In October 2003 in anticipation of closure of the water treatment facility, the draw down and treatment of solution on the leach pad was completed. Following cessation of treatment in the fall of 2003, leach pad solution volume increased to about 25,000,000 gallons by the end of 2004. This accumulation of solution is thought to be the result of continued drain down in the heap leach pad, infiltration of precipitation through the leach pad cover, and from groundwater flow onto the leach pad during the spring snowmelt period and during periods of active LAD water discharge along the north edge of the pad. With the accumulation of 25 million gallons of pad solution, the Forest Service decided to recommission the biological water treatment plant to lower the level of solution in the pad in accordance with the contingency plan that involves active management of the leach pad dike instability issue. The biological treatment system was operated throughout the summer and early fall of 2005 and the volume of pad solution was reduced to about three million gallons by November 2005. In 2006, after a review of water treatment options developed in the initial draft EE/CA (Maxim 2005), a pilot scale reverse osmosis water treatment facility was designed, constructed and field tested by Tetra Tech.

Based on the successful results of pilot scale testing, a full-scale reverse osmosis water treatment facility with a treatment capacity of about 200 gallons per minute was constructed, installed and placed into operation on the Beal heap leach pad in the summer of 2008. From the fall of 2005 to the spring of 2008, the volume of solution on the leach pad had increased to about 90 million gallons. Approximately 12-15 million gallons of pad solution was treated by the reverse osmosis system in its start-up season reducing the volume of water on the pad to about 75 million gallons. An additional 25.4 million gallons of pad solution were treated in 2009. As of October of 2009, there was about 65.5 million gallons of water on the pad; the capacity of the pad is thought to be about 106 million gallons based on a discharge event that took place in December of 1999 in the final stages of the leach pads operation. A review of the rate of accumulation of water on the pad based on the last four periods of dewatering (2003, 2005, 2008 and 2009) suggests an average annual additional accumulation of water on the pad of about 28-34 million gallons per year.

Water collecting in the leach pad must be treated before it can be discharged to surface water or groundwater. Water quality in the pad has changed considerably over the closure and

ES-iv Executive Summary treatment period with most parameter concentrations decreasing except for sulfate, which has increased from 1,440 mg/L in 1999 to, most recently, 2,630 mg/L in 2009. Parameter concentrations that have dropped since 1999 include selenium (0.305 mg/L currently from over

1.5 mg/L), arsenic (currently 0.221 mg/L from over 0.75 mg/L), iron (currently 1.93 mg/L versus more than 20 mg/L), and copper (currently 0.057 mg/L versus over 100 mg/L, a ten-thousand fold drop). Alkalinity has also decreased from about 360 mg/L to about 112 mg/L (CaCO3 equivalent) in March 2005 and to 88 mg/L by August 2009. Total cyanide has decreased from over 200 mg/L in 1999 to about 1.63 mg/L in 2009 (weak acid dissociable cyanide in August 2008 was even lower at about 0.391 mg/L).

Land Application Disposal (LAD) Areas

Solution application to the LAD areas involved historical discharges over 200 million gallons of water to about 31 acres. Application of biologically treated pad solution to the LAD areas began in earnest in 2001 through 2003, and, after an 18 month hiatus, land application of treated heap leach solution was reinitiated in May 2005. A reverse osmosis treatment system constructed in 2008 has also discharged about 37.4 million gallons to an LAD system in 2008 and 2009, albeit with much cleaner water than the previous biological treatment system was capable of producing. In 2004, the LAD areas were used to dispose of water collected in the waste rock dump toe drain and from springs 5 and 10A. This water was also captured and stored over the winter of 2004/2005, and was land applied along with the treated pad solution between May and November 2005.

During the period of discharge to the LAD (2001 to 2006, the last year sampled), selenium and cyanide concentrations that exceed aquatic standards were detected in springs, and iron, selenium, and cyanide were detected in monitoring wells near the LAD areas. In addition, cyanide levels in American Gulch, Beefstraight Creek, and lower Minnesota Gulch down gradient of the LAD areas commonly exceeded the chronic aquatic water quality standard (0.005 mg/L) and occasionally exceeded the acute aquatic surface water standard (0.022 mg/L) over the same time period. In German Gulch the chronic standard for cyanide was routinely exceeded at stations STA-1A and STA-1, both of which are located downstream of the confluence of Beefstraight Creek with the main stem of German Gulch. Since March 2004, no exceedances of the chronic aquatic standard for cyanide have been measured in German Gulch above STA-1A. Cyanide water quality criteria are based on total recoverable concentrations, which include complexed forms of cyanide such as iron complexes. Free cyanide is a much more reliable index of toxicity to aquatic life than total cyanide. While there are no free cyanide data for the Beal Mountain site, weak acid dissociable (WAD) concentrations have been measured to represent cyanide that is considered more bioavailable. These values are generally lower than total cyanide concentration by as much as 30% to more than 100% in German Gulch and Beefstraight Creek. The national recommended acute and chronic water quality criteria for cyanide (0.022 and 0.0052 mg/L, respectively) are based on free cyanide.

With respect to selenium and cyanide values in soil in the LAD areas, data have not been collected since 2000 (Spotts, 2000). Measured sodium absorption ratios at the project site suggest that impacts due to sodium may not be significant. Vegetation data do not show elevated concentrations of contaminants in plant tissue that would be of concern to wildlife or livestock. Visual observations in several areas representative of a range of vegetation communities present in the LAD areas indicate that, overall, the vegetation community is not severely impacted.

Final Beal Mountain Mine EECA - USDA Forest Service, Northern Region ES-v

German Gulch

German Gulch is the receiving stream for the majority of water quality issues associated with the mine facilities and a likely place to measure the success of reclamation efforts at the Beal Mountain Mine. German Gulch and its two main tributaries, Beefstraight Creek and Minnesota Gulch, support populations of native westslope cutthroat trout (recognized as “sensitive” by USDA-FS) and non-native eastern brook trout.

The main impacts to water quality from mine facilities that appear to have potential long-term effects (based on concentrations that exceed chronic aquatic water quality standards) are elevated total recoverable concentrations of cyanide and selenium. Concentrations of cyanide exceed the chronic and occasionally the acute standards for some stream surface water sampling events in 2003 in American Gulch and for several sampling events in 2003, through 2009 in Lower Minnesota Gulch. All but seven samples from Beefstraight Creek exceeded the chronic standard and seven samples exceeded the acute standard for cyanide. These three tributaries are located to the north of the German Gulch divide and drain the areas of most intense LAD application located to the north of the leach pad. Surface water in samples collected from STA-3A in upper German Gulch was also occasionally elevated in cyanide during 2003 through 2009 (above the chronic but below the acute level) and no exceedances in 2009.

Surface water at STA-2 showed two exceedances of the cyanide standard in 2003 and no exceedances in 2004 through 2009, although STA-1 and STA-1A, located below the confluence of Beefstraight Creek (the tributary creek that drains the LAD area) with German Gulch, frequently exceeded the chronic standard for cyanide.

Total recoverable selenium concentrations measured during the 2003 to 2009 period in German Gulch at STA-4 and all stations downstream of STA-3A are below the chronic aquatic life standard for selenium of 0.005 mg/L. At STA-4, selenium concentrations are low because the flow from the toe of the waste rock dump, which contains high concentrations of selenium, is captured before it can enter German Gulch. Concentrations of selenium measured in all of the surface water samples collected during the 2003 to 2009 period from STA-3 and STA-3A exceeded the chronic aquatic life standard, but none exceed the acute aquatic life standard of

0.02 mg/L. Selenium concentrations measured in surface water samples from stations STA-4, STA-3, and STA-3A reached their highest levels between 1997 and 1999 and have generally declined since then. During the 2003 to 2009 period, total recoverable concentrations of most constituents, including arsenic, copper, and zinc, was below chronic aquatic life standards.

Prior to mine development, selenium concentrations throughout German Gulch were considered low with respect to Montana water-quality standards, with readings from non-detect to 0.004 mg/L. With the covering of spring SPR-10A with waste rock, selenium concentrations in German Gulch increased, and remained elevated until recently. The highest concentrations of selenium in German Gulch are typically measured at station STA-3A, with the most recent concentrations of 0.005 mg/L measured in September of 2009. In-stream selenium concentrations have been decreasing since 1996 when water from SPR-10A was captured in a pipeline and discharged to infiltration galleries down stream of STA-3A.

Fish and aquatic macroinvertebrate tissues sampled from the German Gulch sub-watershed did not contain elevated levels of copper but did contain elevated levels of selenium (Selch, 2009).

Mean dry weight selenium concentrations in middle German Gulch macroinvertebrates were above the range of suggested toxic effects thresholds to fish from dietary organisms (3 to 11 micrograms per gram). Selenium concentrations were found to be statistically higher in fish

ES-vi Executive Summary whole-body tissues from middle German Gulch than in fish collected from Minnesota Gulch and Beefstraight Creek. These results suggest a potential pathway for bioaccumulation of selenium in the German Gulch sub-watershed.

Samples collected in the sub-watershed from sediment, fish tissue, fish eggs, and macroinvertebrates in 2002 through 2007 showed selenium elevated above literature values for range of toxic effects in all media sampled in German Gulch but not in Minnesota Gulch and Beefstraight Creek. The hazard rating for selenium in German Gulch was high or moderate for fish eggs and high for macroinvertebrates at all three stations. For sediment, the hazard rating was high at the two upstream stations in German Gulch, but had diminished to none at the downstream station.

Other measures of biological integrity of German Gulch that monitor aquatic life other than fish indicated that impacts from other uses of the area have an impact to streams in addition to those identified with the Beal Mountain Mine. Results of periphyton sampling indicate biotic integrity in the upper and middle reaches of German Gulch in 2001 was generally rated as good, with minor impairment of aquatic life. Other biotic data (algae metrics) indicate relatively unimpaired biota existing in these streams. Aquatic macroinvertebrate data from 1999, 2001, and 2002 indicate generally good biotic conditions, with upper German Gulch classified as moderately impaired during the summer but improved to non-impaired during the fall (McGuire and Weber, 2003). Water quality clearly played a role in limiting macroinvertebrate community biointegrity in upper German Gulch, as most community metrics indicated environmental stress and high macroinvertebrate densities were indicative of nutrient enrichment. Middle German Gulch was classified as non-impaired during both sample events in 1999 and 2001, although scores were lower in 2001 than in previous years. Biointegrity scores relative to macroinvertebrates were slightly lower in 1999 and 2001 than in 1997 for all sample sites, the likely reason being environmental stress related to drought, low streamflow, and declining water and habitat quality. Toxic impacts were not indicated at any site monitored in 2002.

Physical habitat condition for the upper German Gulch location was considered “sub-optimal” in 1999 and 2001 for most habitat parameters (McGuire and Weber, 2003). Habitat quality declined due to reduced riparian plant cover, increased bank erosion, and increased sediment deposition. These conditions appear to have been worsened by drought and livestock use.

Habitat degradation was also attributed to historic placer mine dredging. Both Minnesota Gulch and Beefstraight Creek sampling sites were rated optimal for habitat in 2002.

ALTERNATIVES DEVELOPMENT AND EVALUATION

A number of alternatives were developed to address issues identified at each mine facility.

These alternatives were assembled from general response actions, response technologies, and process options that are appropriate for mine wastes or geotechnical instabilities. A subset of five water treatment options was also developed from a matrix of potential technologies applicable to treatment of waste rock dump seepage. The results of the alternatives analysis is briefly summarized below for the following mine facilities: main Beal Mountain pit; waste rock dump; leach pad; land application disposal areas; and German Gulch. Monitoring was evaluated as an alternative for each of these facilities. There was no significant issues associate with the South Beal pit.

Final Beal Mountain Mine EECA - USDA Forest Service, Northern Region ES-vii

Main Beal Mountain Pit

The two principal issues of concern at the main Beal Mountain pit are geotechnical instability of the pit high-wall and risks to public safety resulting from the high-wall. Failure or continued movement of the clay/sill slide in the high-wall of this pit could be propagated upward into foundation materials of the overlying southern containment dike of the leach pad, posing a potential risk to the structural integrity of the overlying south dike. The risk associated with geotechnical instability of the containment dike is that a failure could breach the lower pad liner, releasing pad solution and spent ore to the environment. A second issue of concern related to the main Beal Pit is the risk to public safety posed by falling from the pit high-wall or injury resulting from rock falling from the high-wall.

Monitoring was evaluated for the main Beal Mountain pit. While monitoring is not solely protective of the environment at this site, it provides a means of detecting changes in conditions that could impact the environment. At the main Beal Mountain pit, monitoring would only detect slide movements that threaten containment dike stability. Monitoring is considered essential at this point in time, however, the effectiveness of monitoring is dependent on the successful implementation of the existing annual operation and maintenance plan for interim dewatering of the clay-sill slide and pad solution removal seasonally when they are required. Monitoring will meet applicable or relevant and appropriate requirements (ARARs) if the slides remain stable without dewatering.

Three alternatives were developed that would be variously effective in the long-term with respect to minimizing risks to public safety. One alternative would prevent human entry to areas of the pit that are subject to landslides and fall hazards using fences and signage, while another would decrease the potential for landslides to occur and would eliminate fall hazards by reduction of the high-wall angle by drill-hole blasting techniques. It appears that drill hole blasting would need to occur from the top of the pit high-wall and would bring down only a minimal amount of material that would be insufficient to construct a buttress to provide additional geotechnical stability for the clay-sill slide within the pit. In addition, in order to get the required angle on the pit, it would likely be necessary begin the new cut slope far enough back from the lip of the high-wall to risk stability of the leach pad containment dike foundation.

Therefore, it appears that this alternative might be an effective means of protecting public safety, without risk to the leach pad facility, only if the leach pad was removed prior to implementing the alternative.

The last alternative involves buttressing the main Beal Mountain pit high-wall to decrease the potential for landslides to occur and would eliminate public safety falling hazards locally in the area of the buttress. This alternative would be effective in stabilizing the clay-sill slide and the leach pad foundation only if the buttress extended high enough and were thick enough on the hill to support the existing buttress adjacent to the clay-sill slide. Such a buttress would require large volumes of material. This alternative is also prohibitively expensive.

Monitoring and public safety alternatives are implementable with standard construction equipment, materials, and earth moving techniques. The total cost for monitoring is estimated at about $65,016. Whereas, the public safety alternative using fencing and signage is estimated to cost $31,984. Alternatives related to both public safety and geotechnical stability are estimated to cost $8,942,978 for reduction of angle on the high-wall, and $8,064,141 for buttressing the clay-sill slide area from within the pit.

ES-viii Executive Summary

Waste Rock Dump

At the waste rock dump, monitoring would not meet ARARs and is not protective of the environment, as it does not address the concentration or loading of selenium from the waste rock dump seepage into German Gulch. Monitoring also does not address the future potential for acid rock drainage (ARD) generation from the waste rock.

Four other alternatives considered for the waste rock dump facility involved either capping and containment scenarios. Two alternatives consider removing waste material from above spring SPR-10A and diverting the flow to minimize contact of groundwater with waste rock. These two alternatives (WR-2A and WR-2B) differ in the amount of material removed from above the spring, the scope of reworking the existing dump, and the cover design. Both alternatives would be effective in isolating groundwater from spring SPR-10A from contact with waste rock and could reduce the selenium load from waste rock seepage by as much as 20%. However, neither alternative will completely reduce the selenium load since there are uncertainties involved with seepage in groundwater beneath the waste rock dump. Alternative WR-2B will have a much greater impact on seepage flow since the entire waste rock dump would be regraded to allow drainage off the slopes rather than infiltration through the waste rock dump.

The waste rock dump would then be covered with an impermeable cap.

Two alternatives would reclaim the upper third of the waste rock dump, which has yet to be completed. These alternatives, WR-3A and WR-3B, would attempt to limit infiltration from this upper and flatter portion of the dump into waste rock. Alternative WR-3A uses a soil cover to achieve this end, while Alternative WR-3B uses a composite cover. As with the WR-2 alternatives discussed above, both Alternatives WR-3A and WR-3B would be somewhat effective in limiting infiltration into the waste rock dump, although the composite cover design used in Alternative WR-3B will be more effective in reducing infiltration and seepage, even though it only covers the upper third of the waste rock dump.

The four cover alternatives have several things in common including: all meet the ARAR for slope stability criteria, with slope regrading under Alternative WR-2B providing the greater slope stability than the other alternatives; each of the alternatives have revegetated surfaces to minimize erosion and maximize evapotranspiration in the covers; each alternative will utilize upgradient diversion ditches to control run-on and berms ,snow-fencing, and/or vegetation barriers to control snow-drifting; and, long-term maintenance requirements for each alternative would be low once vegetation was established.

None of the four alternatives will likely meet surface water ARARs in German Gulch and each are only somewhat protective of the environment in that seepage quality should improve and seepage quantity should decrease. None of the alternatives would reduce seepage concentrations to a degree that would permit discharge of the seepage without prior treatment.

Alternative WR-2B is the most protective of the four and is the most effective in the long-term.

Alternative WR-3A is probably the least effective of the four alternatives.

The costs to implement these alternatives vary considerably and almost directly with protectiveness of the environment and long-term effectiveness. Estimated costs range from about $416,958 for Alternative WR-3A to over $14.3 million for Alternative WR-2B.

Final Beal Mountain Mine EECA - USDA Forest Service, Northern Region ES-ix

Leach Pad

For the leach pad, monitoring would not meet ARARs and is not protective of the environment if pad solution continues to accumulate. Anytime water levels in the pad rise to exceed the recommended volume of 25 million gallons, water treatment will be required to reduce volumes.

Water quality on the pad is poor enough that treatment will be necessary before the pad solution can be discharged from the facility.

Five other alternatives for the leach pad have been developed and these include: replacing the existing cover (LP-2), partial removal of spent ore from the pad (LP-3), complete removal of the spent ore and the containment dike components of the heap leach pad to a new on-site repository (LP-4), and construction of a grout curtain along the northern edge of the heap leach pad (LP-5.

Alternative LP-2 (replacing the leach pad cover) and LP-5 (placing a grout wall [curtain] along the northern edge of the leach pad) address two distinct and likely areas of input of excess solution that is accumulating on the leach pad. As such, both of these alternatives are effective and protective of the environment, and may be most protective and effective if both alternatives are implemented together. However, because the relative amount of water attributable to the cover or groundwater sources is unknown, it may be more practical to construct the grout wall first and then monitor its affect in order to assess the actual amount of water coming through the leach pad cover before replacing it, either in part or its entirety.

Alternatives LP-3 and LP-4 permanently reduce or eliminate the potential for geotechnical instability by moving spent ore to more stable locations, and as such both are effective and protective of the environment. Alternative LP-3 would reposition spent ore from the unstable area at the southwest portion of the leach pad to the northern portion of the pad. Alternative LP- 4 involves the construction of an on-site repository to store spent ore currently held by the leach pad and the contaminated mine waste used to construct the containment dike thus eliminating loading above the unstable area beneath the pad. Alternative LP-3 may be technologically difficult to implement because of the need to remove most of the water from the pad prior to the selective removal of a portion of the spent ore. Partial removal will require expanding the containment dike and obtaining additional soil cover, require upgrading reclaimed roads, and likely create new or reopen former soil borrow areas. However, LP-4 will also require complete removal of water from the leach pad prior to moving the spent ore and containment dike material to a new location. Removal of all of the pad solution will likely require evaporative treatment and sludge disposal of the wastes following RO treatment.

LP-2 and LP-5 each eliminate what is interpreted to be a large but different portion of the water seasonally accumulating on the leach pad and are expected to meet ARARs to varying degrees.

Each of these alternatives would require considerable surface disturbance, large volumes of construction traffic, and all action alternatives would require more than one construction season to implement. Alternative LP-4 may be most effective in that it completely removes spent ore and contaminated wastes to a proposed (but undefined) new on-site repository; as such it should be completely effective, is likely to meet all ARARS, will remove spent ore and wastes used to construct the containment dike from contact with groundwater, and will eliminate the risk from geotechnical instabilities beneath the existing pad. Alternative LP-4 is also extremely expensive to implement.

ES-x Executive Summary

The cost of monitoring the leach pad is about $39,963. The cost to implement Alternative LP-2 (replace existing cover) is about $12,762,734, which is a one-time construction cost for the total replacement of the cover that requires only minor long-term monitoring. If a repair of the cover was determined feasible, this cost could be much lower. Alternative LP-3 (partial removal of spent ore) would cost about $7,132,911, while LP-4 (removal to an off-site repository) would cost about $201,311,444. Finally, LP-5 the grout wall alternative is estimated to cost $4,257,806.

LAD Areas

Only one alternative, monitoring was evaluated for the LAD areas. Monitoring, Alternative LAD- 1, may meet ARARs if only limited future use of the LAD is anticipated and as soluble solutions retained in soils in the LAD diminish in concentration over time. As there are no identified issues with soils or plants at the LAD, monitoring may be an effective and long-term solution.

The cost of monitoring seeps and springs and groundwater monitoring wells in the LAD areas down-gradient of the leach pad is about $44,310. Recent and on-going discharge of much cleaner solutions resulting from RO treatment in areas of historical LAD solution application, are considered a positive approach in that it would encourage additional and faster leaching and rinsing of the remaining CN and Se components attenuated in soils.

German Gulch

As with some of the other monitoring alternatives, Alternative GG-1 will not attain ARARs and is not protective of the environment. Selenium concentrations and loading to German Gulch are not expected to diminish naturally over time without actively addressing sources of selenium.

Alternative GG-2 addresses one potential source of selenium in German Gulch by removing the road fill at the haul road/culvert crossing of the gulch near the main Beal Mountain pit and the Road Fill spring. Removal of this material would be somewhat protective of the environment and somewhat effective in the long-term, although the road fill material is not considered a significant/major of selenium, and therefore, the reduction in selenium loading would be minor.

Removal represents a permanent solution to this problem with only minor short-term impacts from construction in the active stream channel over a very short period of time.

Alternative GG-3A (Seepage Water Treatment) evaluates four treatment options and implements a treatment to remove contaminants from waste rock seepage prior to discharging into a newly constructed LAD area. This alternative would be protective of the environment and would result in a greater reduction of selenium loading compared to GG-2 because more selenium is contributed to German Gulch from waste rock seepage (almost 72% of the total load as measured at SW-3A) compared to road fill.

The four active water treatment options proposed for possible use with Alternative GG-3A require that the seepage be gravity fed to the treatment system. Three of the four treatment options require that a new LAD system be constructed to dispose of treated water. Water treatment options are compared below.

Alternatives GG-3B and GG-3C both propose to discharge waste rock seepage into groundwater infiltration galleries constructed in alluvial materials adjacent to German Gulch using a mixing zone, as defined by MDEQ regulations, to meet water quality standards. Both systems require upgrades to include collection boxes for springs SPR-5 and SPR-10A in the toe

Final Beal Mountain Mine EECA - USDA Forest Service, Northern Region ES-xi drain area and a new pipeline connecting the toe drain seepage collection system with the old MPDES pipeline. Operational upgrades to the old MPDES system pipeline include pipe cleaning and replacement of pressure relief valves. Both alternatives could also capture contaminated spring seepage from natural springs SPR-3, SPR T, and SPR-D5, which would also be effective if the alternative were implemented in conjunction with one of the waste rock treatment or infiltration alternatives. However, these springs account for only 2.5% of total Se-loading to German Gulch.

Both alternatives include diluting the waste rock seepage with water from the main Beal Mountain pit drain to meet groundwater standards prior to discharge to infiltration galleries along German Gulch and have compliance points defined as surface water stations STA-1 or -1A.

These two alternatives differ in the location of the infiltration galleries along German Gulch.

Alternative GG-3B would discharge to existing and reconstructed infiltration galleries in upper German Gulch below STA-3A and with the furthest downstream infiltration gallery being just below STA-2. Alternative GG-3C would extend the existing MPDES pipeline an additional 12,000 feet downstream to the confluence of Beefstraight Creek and German Gulch where it would discharge to two new infiltration galleries.

Both Alternatives GG-3B and GG-3C are effective in meeting water quality ARARs with respect to groundwater standards at the point of discharge and surface water standards at a compliance point chosen at STA-1 or -1A. Under both alternatives, exceedances of the chronic aquatic standards for selenium at stations STA-3 and STA-3A may continue to occur, as neither alternative addresses all existing sources of selenium in the upper portion of German Gulch.

However, implementing Alternative GG-3B may cause the chronic aquatic life standard for selenium to be exceeded at station STA-2 because existing infiltration galleries above STA-2 would be used to discharge in this reach of German Gulch. Water sampling at STA-2 does not indicate impacts from the existing infiltration galleries. Alternative GG-3C would not impact aquatic standards at this location because infiltration of waste rock seepage would occur in groundwater in the German Gulch floodplain at the confluence of Beefstraight Creek. There is a concern that implementation of alternative GG-3C would impact fisheries in the upper reaches of German Gulch because of reduced in-stream flows. However, the contribution of flow to German Gulch from the spring collections system is minimal when compared with in-stream flow, even during low flow periods. MDEQ regulations with respect to mixing zones require that acute aquatic life standards not be exceeded in surface waters near the mixing zone.

Both Alternatives GG-3B and GG-3C will require some level of long-term operations and maintenance, although operation of the system will be passive for the most part. Both alternatives will require long-term monitoring to ensure water quality ARARs are met. In terms of short-term effectiveness, surface disturbances are much greater for Alternative GG-3C, as will be disruptions to users of the German Gulch drainage. Both alternatives should be able to be constructed within one season, however.

The cost of monitoring the German Gulch is about $30,870. The cost to implement removal of road fill (GG-2) is estimated to be about $153,983. The cost to implement Alternatives GG-3B (discharge to existing system) and GG-3C (discharge to extended system) is about $214,648 and $679,243, respectively. Annual O&M costs are the same for both Alternatives, about $19,383.

Implementation of Alternative GG3A (waste rock seepage treatment) would be about $47,686 for peripheral construction costs associated with the treatment alternative and somewhere in the

ES-xii Executive Summary range of $540,000 to $1,680,000 for construction of the actual treatment facility and in the range of $76,000 to $1,440,000 for annual operating and maintenance costs.

Water Treatment

Four water treatment processes were identified for potential implementation at the Beal Mountain Mine site to treat waste rock seepage. These treatment processes could be configured in a variety of ways to treat water on a year-round or seasonal basis. For simplicity, the design treatment plant hydraulic capacities for year-round treatment have been directly adopted from the average annual flow rate without escalation. A detailed review of the site water balance and seasonal flow variations would be required to establish the basis by which average, maximum, and minimum treatment plant hydraulic capacities would be defined; this level of work is beyond the scope of this evaluation. For seasonal treatment, the design treatment plant hydraulic capacity was selected by assuming treatment would take place for four months each year. Only one constituent of concern (selenium) requiring removal to meet effluent discharge goals has been identified for waste rock seepage.

The effectiveness of selenium removal through biological or chemical treatment to consistently meet the effluent discharge goal of 0.05 mg/L will be difficult. Treatability testing would be required to determine the extent of selenium removal possible using chemical or biological treatment processes. Two other treatment options were evaluated for this alternative that treat waste rock seepage by Iron Co-Precipitation (WT-3) and Active Anaerobic Bioreactor Treatment (WT-4). A detailed cost analysis for water treatment options is presented in Appendix D. For total cost, the water treatment option cost should be added to GG-3A alternative cost. Costs associated with sample analysis and system performance reporting is not included in the operating cost estimates for the water treatment options. Alternative GG-3A reports a range of costs based on these two treatment options the latter two alternatives (WT-3 and WT-4).

PREFERRED ALTERNATIVE

Based on the detailed and comparative analysis of the alternatives, a preferred alternative for each mine facility was selected. The preferred alternative and justification for selecting the alternative for each mine facility is presented below.

Main Beal Mountain Pit

The preferred alternative for the main Beal Mountain pit is a combination of monitoring (Alternative MB-1) and an alternative that makes a provision for public safety (Alternative MB- 2A, fencing, signage and land use restrictions). Monitoring will be both protective and effective when implemented in conjunction with the annual operation and maintenance plan calling for dewatering of groundwater in the slide areas and leach pad water treatment on a seasonal basis. Monitoring is capable of identifying either high ground water levels in bedrock or movement of the clay/sill and west-wall slide areas. Monitoring would also be protective if significant amounts of water (>27.5 million gallons, the current condition) accumulates on the pad and water treatment and dewatering plans are implemented. Fencing and signage of the pit high-wall to prevent public access will help minimize the potential for injury due to falls or landslides.

Other public safety alternatives involving blasting to reduce the high wall slope angle (MB-2B) and buttressing the slide area from the interior of the pit (MB-2C) were not selected. These

Final Beal Mountain Mine EECA - USDA Forest Service, Northern Region ES-xiii alternatives are either too dangerous to implement with respect to worker safety and leach pad containment dike foundation stability (MB-2B), or cost prohibitive and do not provide superior protection for public safety compared to MB-2A. Additionally, buttressing the slide area to increase geotechnical stability would be unnecessary following implementation of the preferred alternative for the heap leach pad and is extremely costly.

Waste Rock Dump

Two alternatives considered for the waste rock dump are selected for the preferred alternative.

These include WR-1 (Monitoring) and WR-2B (removal of waste rock cover from Spring 10 A, removal of significant source of selenium to groundwater, regrade, complete cover of dump with composite geo-membrane / soil cover). This alternative should effectively remove a known source of selenium seepage (spring 10A), thereby preventing transport of this component of seepage in groundwater beneath the waste rock. Additionally, this alternative would construct an impermeable (soil/geo-composite) cover of the mine wastes that would significantly reduce infiltration through the wastes and prevent it from contaminating groundwater. Reduction of this infiltration component would therefore, reduce the volume of seepage that delivers selenium and other constituents of concern from the waste rock dump to German Gulch. Continued monitoring of SPR-5, SPR-10A, and the waste rock toe drain water quality would identify whether selenium concentrations from seepage decreased over time and if the potential for generation of acid mine drainage or other geochemical changes were occurring in the waste pile. WR-2A and WR-2B both require moving the upper third of the waste rock dump to a repository/containment area nearby (possibly the leach pad or some other acceptable repository and reclaiming it with a soil cover) in order to minimize the impact of spring SPR-10A buried beneath this portion of the dump. Spring SPR-10A has been dug out and piped to the perimeter of the waste rock dump in the past by Beal Mountain Mining, Inc. with only moderate success and also only represents about 20% of the total selenium load to German Gulch. Re-grading and covering the entire waste rock dump with a composite cover will likely be the most effective alternative reviewed, but is costly. Finally, alternative WR-3A is the least effective of the alternatives considered. At the time of release of this final EE/CA the Forest Service is working cooperatively with the Montana DEQ completing a design to implement waste rock closure alternative WR-3A during the summer of 2010 as an interim action with funding from a Montana Department of Natural Resources and Conservation (DNRC) grant.

Leach Pad Treatment

Any corrective action addressing leach pad issues will need to begin with immediate RO treatment of leach pad solutions. This is essential to prevent water accumulation on the pad from topping the liner system and discharging to the environment (as may have already occurred occasionally along the north edge of the pad and perhaps elsewhere) and also to minimize the risk of a geotechnical failure of the containment dike from the weight of water loading to the clay-sill fault geotechnical instability. Monitoring (LP-1) will be essential during this dewatering period.

Therefore, the preferred alternative for the leach pad is a sequential combination of LP-1 (monitoring), LP-5 (grout curtain), LP-2 (repair or replacement of the leach pad cover), and LP- 3 (partial removal). Implementation of this alternative should proceed in phases that will first address potential, but likely, groundwater input to the pad along the northern edge of the leach pad with a grout curtain (LP-5). Assuming there are still significant amounts of water entering the leach pad following completion of the grout curtain the existing leach pad cover would be

ES-xiv Executive Summary replaced or repaired (LP-2) by installing a new geosynthetic membrane and revegetated soil cover to reduce or eliminate infiltration to the leach pad. This would be followed by a period of monitoring (LP-1) to determine the effectiveness of these two action alternatives with respect to the rate of accumulation of water on the pad. The need for further long-term water treatment and the frequency of treatment could only be assessed after this period of monitoring, however, it is likely that the rate of accumulation of water on the pad would be substantially reduced and may even be essentially eliminated.