PROJECT DESCRIPTION

This project description is based upon the large mine permit amended application submitted to the City and Borough of Juneau by the Coeur Alaska, Inc. (June 1996), and the Final Supplemental Environmental Impact Statement (August 1997), Amended Plan of Operations (August 1997) and revised Reclamation Plan (August 1997) which are considered part of the application.

GENERAL INFORMATION

Applicant: Coeur Alaska, Inc.

Property Owner: U.S. Forest Service; Coeur Alaska, Inc.

Location: Approximately 45 miles north of Juneau and 35 miles south of Haines, on the west side of the Kakuhan Range adjacent to Lynn Canal. (See Figure 1.1, Location of the Kensington Gold Project)

Legal Description: Various patented and unpatented mining claims mainly within Townships 34 and 35 South, Range 62 East, Copper River Meridian.

Site Size: Estimated total disturbed area: approximately 269 acres; total project area controlled by applicant: 8,570 acres.

Zoning: Rural Reserve

Utilities: Private

Access: Lynn Canal to private marine terminal; by air to private heliport

Existing Land Use: Generally undeveloped with some mine exploratory activity.

Surrounding Land Use: North - Undeveloped

South - Undeveloped

East - Undeveloped

West - Undeveloped

INTRODUCTION

Gold was first discovered and claim locations made in 1887 on the Kensington properties. In 1987, Coeur Alaska, Inc. (a subsidiary of Coeur d'Alene Mines Corporation) acquired the Kensington group of properties and formed a joint venture with Echo Bay Exploration, Inc. to explore and develop the properties. In 1988-1990, the Kensington Venture conducted extensive underground exploration work to define mineralized zones at depths previously never evaluated.

In December 1990, the Kensington Venture submitted an initial application to the City and Borough of Juneau (CBJ) for a large mine permit for the "Kensington Gold Project". Following a National Environmental Policy Act (NEPA) review, the U.S. Forest Service approved a Plan of Operations in June 1992. In November 1992, the CBJ Planning Commission issued a Notice of Decision approving the original Kensington mine project.

In July 1995, Coeur Alaska, Inc. became sole owner of the Kensington mine project. Significant redesign of the proposed mine occurred, and Coeur commenced permitting and NEPA approval again in 1996. An amended application for a large mine permit was submitted to CBJ in June 1996. In keeping with the Alaska Supreme Court ruling in Thane Neighborhood Association v. City and Borough of Juneau, CBJ treated Coeur's application as a new large mine permit application. The CBJ current review of the Kensington Gold Project has revisited all aspects of the proposed mine project.

The mine project changes also led to a supplemental NEPA review in 1997, with issuance of a Record of Decision by the U.S. Forest Service in August 1997. Approval of an amended Plan of Operations by the U.S. Forest Service, as well as other major State and federal permits and approvals are pending.

Currently, the Kensington mine has a projected life of about 12 years. Construction activities would take about two years, gold production for the next 12 years, and decommissioning and reclamation during the last two years. Underground exploration activity will be conducted each year with the objective of replacing the gold reserve which is depleted through mining operations.

The ore will be concentrated at the mill site and shipped from the Comet Beach marine terminal for gold refining elsewhere. Tailings from the mill will be transported via slurry pipeline to a filter plant and dewatered for disposal in a engineered dry tailings facility located between Sherman Creek and Sweeney Creek.

At a production rate of 4,000 tons of ore per day, or about 1.4 million tons per year, gold recovery will be about 200,000 troy ounces per year. Operation of the mine would take place 24 hours per day, 365 days per year with a workforce of about 275 persons.

LOCATION AND TOPOGRAPHY

The Kensington Gold Project is located on the west side of the Kakuhan Range in the Tongass National Forest adjacent to the Lynn Canal. The mine site is approximately 45 air miles north of Juneau and 35 air miles south of Haines, Alaska.

The planned mill site and mine area lie between Ophir and Sherman Creeks at the western base of Lions Head Mountain. The hill above the site is referred to as the "Horrible Hill," after an abandoned mine located in the area. Steep and rugged mountains surround the planned Kensington site. The area between the mine portal and the Lynn Canal is characterized by 5 to 35 percent slopes and alluvial fans dissected by the drainage.

The Sherman Creek drainage is a second growth rain forest. The canopy consists of coniferous forest vegetation interspersed with muskeg bogs and alder. Field surveys documented that wetlands exist on all but the steep slopes within the project area.

PROJECT ACCESS

Access to the mine site is limited to air and water; no road access exists. Mine personnel will be transported primarily by helicopter operating between the Juneau airport and a heliport at Comet Beach at the mine site. On average, two to four flights per day, 7 days per week will occur during operations, with more frequent flights during mine construction.

Large quantities of equipment and supplies will arrive by barge transport from Juneau and Seattle. Diesel fuel will be delivered in bulk by fuel barges arriving about once a week. Other fuels will be delivered in containers by barge. Barges will also load containers of ore concentrate for shipment off-site.

SURFACE FACILITIES

Coeur's application states that approximately 269 acres will be disturbed by the construction and operation of the project. This disturbance will be on both the applicant's private land and on unpatented mining claims located on Forest Service land. A number of surface facilities will be constructed for the Kensington Gold Project. These facilities and the estimated surface disturbance include the following:

Marine Terminal Complex

A marine terminal facility will be located at Comet Beach. This facility will be constructed to permit year-round delivery of fuel, materials, supplies, and personnel.

The barges will unload materials and supplies via a 50-foot long ramp of pre-cast concrete planks on a slope tied into bedrock. Fuel barges will unload at a site north of Comet Beach by tying up to mooring buoys and pumping fuel to onshore storage tanks via floating pipelines.

The Kensington site can be accessed only by sea or by air. For this reason, a large (350 by 150 foot) staging and storage area will be located at the marine terminal for temporary storage of equipment and supplies transported to the site by barge. Ore concentrate will also be stored here in 4 foot x 8 foot x 20 foot marine transport containers prior to barge shipment off-site.

Fuel Storage/Laydown Area

Three types of fuel will be stored on site: diesel, aviation fuel, and gasoline. Diesel will be used for power generation at the main power plant, in several small generators, the diesel driven fire pump, and all mobile equipment. A 300,000 gallon tank will be located in a lined containment area at the marine terminal. Diesel will be pumped to another 300,000 gallon tank at an additional laydown area located adjacent to the mine access road immediately above the marine terminal complex. Diesel will then be distributed by fuel truck to two 300,000 gallon tanks at the mill process area. Aviation fuel will be required for the helicopter and delivered in iso-tainers for storage at the marine terminal. Limited amounts of gasoline will be brought containerized to the site for use in small engines.

Heliports

Personnel will be transported by helicopter operating between the Juneau airport and the site. The primary heliport is located at the marine terminal. A secondary helicopter landing pad will be located adjacent to the employee camp and process area two miles inland from the shoreline at approximately 800 foot elevation. A helicopter landing pad located near the 2,000 foot portal will be used for emergencies and to support mine operations.

Access Road

An existing access road will be widened to a 60-foot width to accommodate the road traffic between the marine terminal and the 850 foot elevation mine portal. The road will also serve as the corridor for the tailings slurry and return water pipelines. Vehicle traffic will include personnel movement, fuel trucks, borrow material haul trucks, maintenance vehicles, camp/warehouse supply vehicles, and explosives transport.

Additional side roads will be required at intervals along the road to access such facilities as the laydown area, explosives storage site, Dry Tailings Facility, and Filter Plant.

Process Area

A centralized process facility will be located adjacent to the 850 portal area. This process service complex will include the following: mill (designed to process 4,000 tons per day), warehouse, main maintenance shop, administrative offices, miners change facility (dry), power plant, and metallurgical laboratory. The power plant will be insulated to minimize noise impacts of the four diesel-powered generators.

In addition to the removal of ore, about 400 tons of non-mineralized rock, called development waste rock, will need to be excavated daily to gain access to the vein system. Waste rock will be removed from the mine using 33 ton haul trucks. Initially, this development waste rock will be transported to a five acre site near the 850 level portal. It will be used in the construction of the tailings facility and in road maintenance, and some will be disposed of underground in mined-out stopes.

Employee Camp

Tentative work schedules will require that at least half of the full compliment of work personnel be on site at any one time. The camp is sized for 250 persons, providing spare rooms for exploration crews, catering, visitors, and other extra staffing requirements at the site. The camp will be located adjacent to the process area.

Borrow Sites/Topsoil Stockpiles

Four borrow pits will provide sand, gravel, and till for mining operations. Several small topsoil stockpiles are also planned, with some topsoil used during interim reclamation after initial mine construction. They will be located in the general vicinity of the mill process area. The till and development waste rock will be used in construction of the Dry Tailings Facility.

Mine Portal Areas

The underground mine workings will be accessed primarily through the existing mile-long adit located at about 850 feet above sea level. A second portal, adjacent to the 850 portal, will provide access and ventilation. A third and possibly fourth portal are located at approximately the 2,050 foot level. This smaller portal area is utilized mainly as a ventilation exhaust. The fifth portal will be located east of the mill facility and contains the conveyor system which delivers ore from the underground crusher to the 8,000 ton coarse ore stockpile. This portal also provides ventilation and secondary exhaust.

MINING METHOD

The applicant's proposal describes an underground extraction technique called long hole, open stoping. This mining method is used where the ore occurs in steeply dipping, wide vein deposits. This method requires strong ore and wall rock to support the stope without additional mechanical roof control. It efficiently removes ore while providing for separation of waste necessary to ensure a high rate of resource recovery (80 to 90 percent). Dilution of ore is minimal. The method uses bulk material handling for higher productivity. Mining would proceed from the top of the ore body downward.

The method incorporates high worker safety by limiting exposure to unsupported ground conditions. The method also provides for good ventilation.

Future development can be safely completed along strike and dip to recover additional undiscovered ore. The recovery of pillars by mass blasting will cause the hanging wall to cave and will also relieve stress on adjoining workings. Subsidence at the surface is not expected due to the bulking effect of the broken material and the minimum 150 foot crown pillar which would be left to ensure stability.

ORE PROCESSING

The processing facility for the Kensington Project is segregated into three primary areas. The crushing operation will be located underground. The grinding, flotation, and thickening processes will be located on the surface at the process area. The filtering process will occur at the filter plant located adjacent to the dry tailings facility. The flotation process separates the gold bearing minerals from the barren rock. The resulting flotation concentrate is dewatered, loaded into containers, and trucked to marine terminal for storage until transshipped by barge off-site for final ore processing.

TAILINGS DISPOSAL

Once the gold-bearing minerals are extracted in the flotation process, the remaining barren rock -- or tailings -- is thickened. Tailings at the Kensington Project will be comprised of finely ground rock fragments with a consistency of beach sand. Coeur Alaska, Inc plans to construct an engineered and layered pile for disposal of most of the tailings on a terrace above Lynn Canal.

A thickened tailings slurry will be pumped about 1.5 mile via a 10 inch diameter pipeline alongside the main access road to a filter plant adjacent to the dry tailings facility. A road approximately 20 feet wide will be maintained from the main access road to the DTF. The tailings slurry will be dewatered to about 18 percent water by weight. Tailings will be trucked a short distance from the filter plant to the leading edge of the DTF.

The tailings pile will be constructed in three phases, or cells, with a series of 28 foot lifts covered with till and development rock. The outer edge of the facility will consist of a compacted layer of tailings, covered with till, development rock, and topsoil. On the downslope sides of the tailings facility (West and South), an engineered berm of rock and till will also be constructed. The compacted "skin" and berm are designed to contain the mine tailings, in the event they became saturated or an earthquake causes settling. Topsoil material will be placed on the external slope of the berm or compacted edge of the tailings facility, and plans call for revegetation to prevent soil erosion and to encourage native vegetation.

A minimum of 25 percent of the mine tailings will be taken from the thickener at the process area and pumped up to a paste backfill plant inside the mine. The tailings will be filtered and cement added to create a paste that will be placed in mined out stopes underground. Coeur will conduct on-going evaluations designed to increase the amount of tailings backfilled underground.

WATER SUPPLY AND MANAGEMENT

An infiltration gallery will be constructed in Sherman Creek upstream of the process area to obtain potable water for the employee camp and process facilities. Water will be pumped from the infiltration gallery to a 300,000 gallon storage tank at the mill site where it will be distributed to the various facilities. Water used in the mine process will be recycled and reused in ore processing. Gray water from the camp facilities will be treated and discharged in a leach field adjacent to the employee camp.

Water managed at the project site will consist of four types: mine drainage, stormwater, surface water, and dry tailings facility drainage. The only mine drainage water will be groundwater intercepted by the underground mining and water used for drilling and dust control. This water will be collected, pumped to the surface, and processed through a chemical and filtration water treatment plant and routed to mine settling pond adjacent to the process area.

Surface runoff from the process area will also be collected -- as separate contact and non-contact waters -- and routed to the mine settling pond or stormwater settling pond, depending on whether the water came in contact with development rock and the mill, maintenance shop, or fueling areas. These storm waters will be treated according to the federal NPDES permit requirements prior to discharge into Sherman Creek.

Ophir Creek will be diverted to Ivanhoe Creek during mine operations to avoid the till borrow source. At mine reclamation, the diversion will be removed and water flow rerouted back to Ophir Creek.

Construction of the Dry Tailings Facility will include an upslope diversion to intercept surface water before it enters the facility. These waters will be routed around the DTF to an intermittent stream. Water draining from the DTF will be collected and routed to a treatment pond and discharged to Camp Creek.

RECLAMATION

The applicant's reclamation plan, revised in August 1997, identifies several objectives:

• o Stabilize and protect surficial soil materials

  o Establish self-sustaining vegetative communities

  o Establish pre-mining land uses and resources, including wildlife habitat and recreation consistent with visual quality objectives and a USFS visual priority travel route (Lynn Canal)

  o Protect surface water and ground water quality and fish habitat

  o Protect public health by eliminating potential hazards such as access to mine workings after closure

  o Maintain recreational resources

  o Stabilize steep slopes through recontouring and leveling

  o Develop open water habitat

  o Alleviate long-term closure requirements, especially to minimize ongoing maintenance

Ultimately, the company's goal is to "...return the disturbed areas to a stable and productive condition meeting the requirements of the USFS Tongass Land and Resource Management Plan Modified Landscape classification in a safe manner."

MONITORING

The applicant's Amended Plan of Operations (August 1997) describes a monitoring plan which addresses three discrete phases: predevelopment, operational, and closure/reclamation. The overall environmental monitoring plan is designed to provided a continuum of data for comparing existing background conditions with project-related changes. Monitoring sampling frequency, parameters, and reporting requirements are specified in an array of agency permits and approvals governing the Kensington Gold Project. As part of the project, Coeur will monitor groundwater and surface water quality, aquatic resources, wildlife, air quality, dry tailing facility, visual resources, noise, and reclamation.

EMPLOYMENT AND WAGES

During the 22 months of construction, Coeur Alaska, Inc. and construction contractors will employ up to 500 people for construction and development activities. Worker earnings during the two years of mine construction are estimated at about $28 million. At full production (about 3 to 6 months after construction is completed), project employment will range between 250 and 274. Total annual mine employee wages during mine operations are estimated at $11.4 million in 1996 dollars. Based on the Final Socioeconomic Impact Assessment for the Kensington Gold Project, an estimated 187 indirect jobs would also be created in the Juneau economy during the operating life of the mine.

As the mine operations cease, an estimated work force of about 100 people will be used to salvage equipment and dismantle project facilities for removal. In the following spring and summer, about 50 workers will be needed to complete surface reclamation activities.

Return to Kensington Mine Review Page
Return to the Capital City Home Page

Our URL is http://www.juneau.lib.ak.us/cdd/Kensingt.htm