Stillwater Mining Company Tailing Impoundment Expansion, Stillwater County, MT

DEPARTMENT OF AGRICULTURE

Forest Service

Stillwater Mining Company Tailing Impoundment Expansion,

Stillwater County, MT

AGENCY: Forest Service, USDA.

ACTION: Notice; intent to prepare an environmental impact statement.

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SUMMARY: The USDA, Forest Service, as co-lead agency with the Montana

Department of Environmental Quality (MT DEQ) will cooperatively

participate in the preparation of an environmental impact statement

(EIS). The EIS will disclose the environmental effects due to

construction and operation of a new tailing impoundment facility

located approximately 7 miles northeast of the present Stillwater Mine

facility. The area involved in this proposal involves both federal

land, administered by the Forest Service, and private lands over which

the MT Department of Environmental Quality has jurisdiction.

The Director of the Montana Department of Environmental Quality and

the Custer National Forest Supervisor are the officials responsible for

approving SMC's proposal to construct and operate its tailing storage

facility and other associated structures which are discussed in this

Scoping Statement.

The Forest Supervisor has the authority for regulating all

activities and uses of National Forest system lands. The Custer

National Forest Supervisor will decide whether to approve Stillwater

Mining Company's amendment to their approved Plan of Operations as

detailed in the Proposed Action, or whether to approve an alternative

to the Proposed Action. The Forest Supervisor also has the ability to

prescribe mitigation measures as conditions of approval.

DATES: A public meeting will be held in Absarokee, MT on September 24,

1996 in order to identify issues to be addressed in this environmental

analysis. Written comments concerning the scope of this analysis must

be received by October 31, 1996.

ADDRESSES: Written comments concerning this analysis should be sent to

Rand Herzberg, Beartooth District Ranger, Custer National Forest, HC

49, Box 3420, Red Lodge, MT 59068.

FOR FURTHER INFORMATION CONTACT:

Questions about the proposed action and EIS should be directed to Pat

Pierson, Interdisciplinary Team Leader, Beartooth Ranger District.

Phone (406) 446-2103.

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SUPPLEMENTARY INFORMATION:

Purpose and Need for Action

The Stillwater Mining Company has been in operation since 1986. SMC

is currently in the process of expanding ore production from 1000 tons

per day to 2000 tons per day. At the present rate of production, SMC's

permitted tailings impoundment will reach its ultimate capacity by the

year 2003.

Given the projected life of the current tailing facility, SMC must

proceed with the permitting of an additional tailings storage options

in order to provide the capacity needed to manage tailings and waste

rock in the long term. The purpose of this Proposed Action is to permit

an integrated waste management plan to provide for the long term

management of SMC's waste stream.

SMC has submitted a proposal to amend its plan of operations in

accordance with Federal and State regulations. The General mining law

of 1872 grants all US citizens the right to explore, develop, and

produce mineral resources on Federal lands open to mineral entry. SMC

currently operates the only economically viable platinum/palladium mine

in the western hemisphere, and accounts for five percent of world

production. Thirty-five percent of US consumption of platinum/palladium

is accounted for by the automotive industry in catalytic converters,

required as a result of the Clean Air Act of 1990, 32 percent by

electronics, nine percent is used for medical/dental purposes, six

percent by the chemical industry, and 18 percent is used for a variety

of purposes, based on their chemical inertness and refractory

properties (USDI, 1991).

The purpose of this environmental analysis is to disclose the

environmental effects of Stillwater Mining Company's Proposed Action

and alternatives to that Proposed Action. Although effects of other

potential activities within the Stillwater Complex are included in this

analysis, the decision document resulting from this environmental

analysis will make a decision only on the proposed expansion.

Description of Proposed Activity

The Stillwater Mining Company has submitted a proposal to the

Forest Service and the Montana Department of Environmental Quality to

construct and operate a new tailing impoundment at the Hertzler Ranch.

The Hertzler Ranch is situated approximately seven miles northeast of

the mine site. Construction of the Hertzler Impoundment would utilize

local borrow materials, therefore this amendment proposes to store

waste rock on permitted waste rock sites located on the east side of

the Stillwater River. This area is currently occupied by a part of the

mine waste water disposal system, known as the Land Application and

Disposal system (LAD). Once construction begins on the east side waste

rock storage area, the LAD system would be moved. To insure that

production levels can continue uninterrupted and that operational

flexibility is maintained, SMC will continue to utilize the existing

tailing impoundment. As currently proposed, the two impoundments would

be operated in concert.

This amendment proposes to expand the current permit area to

include the Hertzler Ranch. The existing mine permit area encompasses

approximately 1,340 acres. Within this area, approximately 255 acres

will ultimately be disturbed by permitted mining activities. Of this

255 acres of disturbance, well over 120 acres have been disturbed by

past mining and exploration activities. This amendment will result in

approximately 271 acres of additional disturbance and will increase the

total permitted acreage by 1,112.

Past amendments to SMC's original Plan of Operation have utilized a

defined production rate as a means to quantify and qualify the possible

environmental impacts due to construction and operation of the mine

facility. This approach has limited SMC's operational flexibility and

made it difficult to take advantage of the economic scale inherent

during mine expansion. Consequently, this amendment proposes to

establish a project footprint within production rates, but will be

variable as dictated by project economics and infrastructure capacity.

Tailing Impoundment

Construction of the proposed tailing embankments will incorporate

staged expansion using local borrow materials, identified during the

1981 site investigation program. The embankment would be constructed

using the centerline method to a height of approximately 155 feet

(elevation 5,036 feet) at the deepest section and would accommodate

storage of approximately 13 million cubic yards (12.3 million tons) of

tailings. This facility will cover approximately 146 acres after

construction.

SMC is proposing to utilize a high density polyethylene (HDPE)

liner within the impoundment. A system of spine underdrains would be

incorporated to promote consolidation of the tailings mass during

operations. Seepage collected from the underdrains and from the

embankment filter drains would drain to recycle ponds situated around

the perimeter of the facility. From the recycle ponds, this tailings

water would be pumped back to the tailings impoundment for reuse in the

milling and concentrating process.

Reclamation of the outer embankment slope will be conducted

concurrently with operations of the facility, thereby minimizing

impacts and fugitive dust. A minimum of 12 inches of soil and/or sub-

soil will be stripped and stored for final reclamation prior to the

excavation of the impoundment or borrow areas. Final reclamation of the

waste storage site will incorporate waste rock and vegetation in a

mosaic pattern similar to that permitted on the existing tailing

impoundment.

Post closure settlement is predicted to vary between 1 to 10 feet,

depending on the distribution and final depth of tailings within the

impoundment. Therefore, an average surface capping layer of

approximately five feet will be required (including two feet of

topsoil).

Mine Waste Rock Production and Management

Waste rock from the mine which is not used for construction of

portal pads, roads, mine backfill, or other uses, has typically been

utilized in the construction of the tailing embankment. However, due to

the long haul distance between the place of waste rock origin (mine

location south of Nye) and the place of use (Hertzler location) waste

rock will not be utilized in the construction of the new tailings

impoundment. Therefore, this proposal includes provisions to increase

the size of the east side waste rock pad and visibility berm permitted

in the 2,000 tons per day Environmental Impact Statement and Record of

Decision. Expansion of the East Side waste rock storage site would add

approximately 10 million cubic yards of storage capacity and would

encompass an area of approximately 80 acres.

The East Side waste rock facility would be constructed in a phased

approach as outlined below:

Stage 1 Construction

Will consist of the placement of a visibility and containment berm

to approximately the 5,000 feet elevation level. This visibility berm

would be constructed to approximate a natural feature. Vertical and

horizontal relief will vary in order to break up visual lines.

Once completed, the visibility and containment berm will be

topsoiled and revegetated. The toe of the berm will be placed a minimum

of 100 feet from riparian zones.

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Embankment slopes will vary between 3h:1v to 2h:1v, with shallower

slopes maintained along the Stillwater River corridor to minimize

erosion during potential maximum flood (PMF) events. Erosion control

will be provided through revegetation of the berm and by placing rip

rap in drainage areas to prevent stormwater run-off. Existing

monitoring wells and piezometer locations covered by the waste

stockpile construction will be either relocated, capped, or extended.

A portion of the emergency pipeline containment pond, which was

designed to contain stormwater and spillage from the pipelines crossing

the Stillwater River, will be partially inundated by the Stage 1 berm.

The remaining storage capacity in this area will exceed one million

gallons and will provide over 41 hours of emergency storage at a

pumping rate of 400 gallons per minute.

Stage 2 Construction

Construction would continue as in Stage 1. The berm would continue

to be located a minimum of 100 feet from riparian vegetation.

Construction would continue to resemble a natural feature by varying

horizontal and vertical lines. Embankment slopes would vary between

3h:1v to 2h:1v. Monitoring wells, storm water collection ponds, and toe

ditches will be added along the downstream slopes of the waste

embankment. Montana Power's utility line would be relocated to the

downstream toe of the embankment.

Stage 3 Construction

During the Stage 3 construction phase, the waste rock storage area

will be raised to approximately the 5,050 feet elevation, with no

further extension of the Stage 1 and Stage 2 toes. The visibility and

containment berm would be constructed with slope gradients varying from

3h:1v to 2h:1v and revegetated. Waste rock placement would be conducted

in lifts behind the berm and each lift would be graded and compacted by

a dozer. The compaction of each lift will minimize fugitive particulate

emissions from the pad and water infiltration due to precipitation.

Selective shaping of the top cap will sculpture areas of the embankment

to approximately the 5,080 ft. elevation. By varying the elevation of

the cap, the final pad would blend with the natural terrain.

Pipeline Systems

The pipeline system will consist of five pipelines and extend for

approximately 34,000 feet. Two pipelines will be dedicated for slurry

transport, one pipeline for mine water (LAD), one for return reclaim

process water and one line will be utilized as a spare. The pipelines

will range from 6 to 12 inches in diameter. The pipeline system will be

located along Stillwater County roads 419 and 420 right-of-way and be

buried at a depth of approximately five feet (below the frost line).

The pipeline system will include flow, moisture, and pressure

instrumentation along with inspection ports of physical pipe wear

measurements. In areas of potential environmental concerns the pipeline

system will be either double lined and/or placed in a conduit system.

Emergency containment facilities will be placed on both sides of river

or stream crossings and near any booster pumping station.

Pipeline material will be either steel or high density polyethylene

(HDPE). HDPE offers advantages of lower friction, greater abrasion

resistance, no corrosion problems, and generally lower installation and

purchase cost. A HDPE pipeline would require the installation of a

booster pump station due to the line pressure restrictions inherent to

HDPE pipe.

Steel pipe offers an advantage over HDPE with its ability to

support higher pressures. Use of an all steel pipeline could allow a

single high pressure pump station to be installed at the thickener,

eliminating the need for a booster pump station somewhere along the

pipeline corridor. A collection pond together with a reclaim system

would be required at the mid-point of the line. This facility would

allow for a pipeline to be drained in the event of a line rupture.

Reclamation will be conducted concurrently with pipeline

construction. Following compaction of fill over the pipelines, 12

inches of salvaged soil will be replaced and seeded. Seeding of the

reclaimed pipeline trench will conducted utilizing SMC's approved low

elevation seed mix.

Forest Plan Direction

The area involved in this proposal is within Management Area E as

described in the Custer National Forest Land and Resource Management

Plan (1986). The management goal for Management Area E is as follows:

To facilitate and encourage the exploration, development, and

production of energy and mineral resources for the National Forest

System lands. Other resources will be considered and impacts will be

mitigated to the extent possible through standard operating

procedures, and on a limited basis, through special lease

stipulation necessary to manage key surface resources. Energy/

mineral development will not be precluded by these resource concerns

within legal constraints. Efforts will be made to avoid or mitigate

resource conflicts. If the responsible official determines that

conflicts cannot be adequately mitigated she/he will resolve the

conflict in accordance with the management goal and, if necessary,

in consultation with affected parties (Forest Plan, page 58).

Preliminary Issues

The Forest Service and Department of Environmental Quality

Interdisciplinary Team (IDT) has preliminarily identified five issues

which will be addressed in the environmental analysis. These issues

have been identified due to the possibility that the existing

environmental conditions related to these issue areas may change as a

result of the construction, operation, and reclamation of the Hertzler

Tailing Impoundment facility. These issue areas include;

Water Quality and Quantity; Aesthetics (Including Noise, Air

Quality, and Visual Effects); Tailing Impoundment Stability; Social/

Economic Effects; and Wildlife and Fisheries.

Preliminary Alternatives

Potential tailing impoundment locations for Stillwater Mining

Company's mine have been explored since the early 1980's. These

previous site investigations include those conducted by Wahler

Associates (1981), the US Forest Service and the Montana Department of

State Lands during development of the 1985 EIS, the US Forest Service

and the Montana Department of State Lands during the development of the

1992 EIS, and recent investigations, undertaken by Knight Piesold for

this proposed amendment to SMC's Plan of Operations.

After reviewing past studies, Knight Piesold (1996) concluded that

the evaluation process should be expanded to include consideration for

the disposal of both tailing and waste rock in the overall waste

management strategy. As a result of the 1996 Knight Piesold

investigation, four waste management alternatives were selected for

further study by Knight Piesold. The four management alternatives,

incorporating tailings impoundment options selected from the previous

assessments are summarized below:

Option A: Expansion of the existing tailing impoundment by Modified

Centerline construction, with concurrent development and operation of a

new tailing facility at the Hertzler Ranch site.

Option B: Expansion of the existing tailing impoundment by

Centerline construction and extension of the

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downstream toe, and concurrently development and operation of a new

tailings facility at the Hertzler Ranch site.

Option C: Expansion of the existing tailing impoundment by Modified

Centerline construction, and concurrent development and operation of a

new tailings facility located on the East Side of the Stillwater River.

Option D: Development of a new tailings facility at the Hertzler

Ranch site, with some tailings disposal into the existing permitted

impoundment when required to facilitate ease of operations (Proposed

Action).

Each of these alternatives includes development of a new tailings

impoundment and expanded waste rock storage capacity in order to

provide sufficient storage for long term operations.

EIS Availability

The draft environmental impact statement (DEIS) is expected to be

available for public review during the spring of 1997. After a 45 day

public comment period, the comments received will be analyzed and

considered by the Forest Service and Montana Department of

Environmental Quality during the preparation of the final environmental

impact statement (FEIS). The FEIS is scheduled to be completed by the

fall of 1997. The regulatory agencies will respond to the comments

received in the FEIS. The Custer National Forest Supervisor and the

Director of the Montana Department of Environmental Quality are the

responsible officials for this EIS and will make a decision regarding

this proposal considering the comments and responses, environmental

consequences discussed in the FEIS, and applicable laws, regulations

and policies. The decision and reasons for the decision will be

documented in a Record of Decision.

The comment period on the draft environmental impact statement will

be 45 days from the date the Environmental Protection Agency publishes

the notice of availability in the Federal Register.

The Forest Service believes it is important to give reviewers

notice at this early stage of several court rulings related to public

participation in the environmental review process. First, reviewers of

draft environmental impact statements must structure their

participation in the environmental review of the proposal so that it is

meaningful and alerts the agencies to reviewer's position and

contentions. Vermont Yankee Nuclear Power Corp. v. NRDC, 435 U.S.

519,553 (1978). Also environmental objections that could be raised at

the draft environmental impact statement stage but that are not raised

until after completion of the final environmental impact statement may

be waived or dismissed by the courts. Wisconsin Heritages, Inc. v.

Harris, 490 F. Supp. 1334, 1338 (E.D. Wis. 1980). Because of these

court rulings, it is very important that those interested in this

proposed action participate by the close of the 45 day comment period

so that substantive comments and objections are made available to the

Forest Service at a time when it can meaningfully consider them and

respond to them in the final environmental impact statement.

To assist the Forest Service in identifying and considering issues

and concerns on the proposed action, comments on the draft

environmental impact statement should be as specific as possible. It is

also helpful if comments refer to specific pages or chapters of the

draft statement. Comments may also address the adequacy of the draft

environmental impact statement or the merits of the alternatives

formulated and discussed in the statement. (Reviewers may wish to refer

to the Council on Environmental Quality Regulations for implementing

the procedural provisions of the National Environmental Policy Act at

40 CFR 1503.3 in addressing these points.)

Dated: September 11, 1996.

Nancy T. Curriden,

Forest Supervisor, Custer National Forest.

[FR Doc. 96-24444 Filed 9-23-96; 8:45 am]

BILLING CODE 3410-11-M