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Reclaimed Flambeau Mine

The department has received Flambeau Mining Company's petition for a certificate of completion of reclamation for the remaining 32 acres of the permitted mine site. A hyperlink to a copy of the petition is available below on the 'Industrial Outlot' tab.

While there are other examples of successfully operated and reclaimed metallic mines in Wisconsin, the Flambeau Mine near Ladysmith in Rusk County is the only example of a metallic mine that was permitted, constructed, operated and reclaimed under the state's existing regulatory framework.

The open-pit, copper-gold mine began operations in July 1991, and reclamation activities were substantially completed by the end of 1999. As specified in the Reclamation Plan and Mining Permit, the open-pit was backfilled with waste rock and other materials removed during the mining process. The backfilling process involved blending the stockpiled waste rock with a prescribed amount of limestone. Limestone, because of its neutralization capacity, was used to neutralize any acidity that developed while the rock was stored in the waste facility and also to minimize the potential for the development of acid conditions prior to reflooding. Once groundwater saturated the backfilled material, the threat of ongoing acidification was largely eliminated.

The DNR gained valuable experience in its review and oversight of the Flambeau Mine and will continue to gather additional information as monitoring of the reclaimed site continues for the next several decades.

History

Project history

Late in 1968, based on favorable indications from an airborne geophysical survey, Great Lakes Exploration Company, a subsidiary of Kennecott Minerals Company, drilled the first exploration drillhole into the Flambeau deposit. During the next several years, more than 100 additional holes were drilled into the deposit to define the grade, size and orientation of the deposit. The Flambeau deposit was delineated as a near vertically oriented tabular-shaped copper-gold deposit approximately 50 feet wide, 2,400 feet long and extending to a depth of about 800 feet. The deposit contained about six million tons of ore comprised of more than 50 percent sulfide minerals, primarily pyrite (iron sulfide), with concentrations of the copper-bearing minerals chalcocite, bornite and chalcopyrite. In addition, the weathered upper portion of the deposit contained higher grades of copper and significant concentrations of gold.

An aerial view of the Flambeau Mine during active mining operations.
An aerial view of the Flambeau Mine during active mining operations. The Flambeau River is located in the southwest corner of the photograph.

Beginning in 1974, Kennecott Minerals Company initiated the process to obtain a mining permit in accordance with the newly adopted Metallic Mining Reclamation Act. The project, as proposed in the mid-1970s, involved mining the ore body in two phases, an 11-year open pit phase followed by an 11-year underground mining operation. The plan called for concentrating the ore on site with a tailings disposal facility located approximately two miles to the south of the ore body.

Upon completion of mining, the open pit would have been allowed to fill with water and the remainder of the site would be revegetated. The company submitted an Environmental Impact Report to the DNR. The DNR subsequently prepared and released an Environmental Impact Statement. During the final permit hearing in 1976, Rusk County officials indicated they would not grant zoning approvals due to various concerns regarding the mining project and the state's mining and mining tax laws. Since the local jurisdictions indicated they would not approve the project, the state’s permitting process was terminated because local approvals were a pre-requisite to issuance of the necessary state permits and approvals. Kennecott later put the project on hold as a result of the suspension of the permitting process and poor global metal markets that existed at the time.

In 1986, Kennecott reevaluated the project and determined that a redesigned, scaled back project could be viable. Under the revised plan, only the enriched upper 225 feet of the deposit would be mined through a small open pit mining operation. Because of the high grade of this material, it was determined to be economically feasible to ship the ore directly to facilities in Canada for further concentration and smelting, thereby avoiding the need for construction of a mill and tailings disposal facility at the project site. In addition, the company proposed to completely fill the pit with waste rock stored on the surface during the mining operation. Limestone would be blended with waste rock prior to backfilling.

Flambeau Mining Company, another subsidiary of Kennecott, restarted the permitting process for the project in 1987. After a three-year process involving baseline data gathering, negotiations with local units of government, project design and technical review, the DNR issued the Final Environmental Impact Statement for the project in 1990. A contested case permit hearing was held amid a high level of public input and controversy and the administrative law judge subsequently issued all required permits in early 1991. Construction at the project site began in the summer of 1991. Site preparation, facility construction and mine development continued for about two years and ore shipments from the site began in 1993 and continued for more than four years. Backfilling of the pit took about 1.5 years and reclamation activities at the site were substantially completed by the end of 1999.

Project description

Project description

Haul trucks removed ore from the Flambeau Mine.
Haul trucks removed ore from the Flambeau Mine.

The 181-acre mining site is located about one mile south of Ladysmith and bounded on the east by State Highway 27 and on the west by the Flambeau River. Prior to construction of the mining facility, the site consisted of active agricultural lands, old farm fields and forested areas. Several intermittent streams flowed through the site to the Flambeau River, and about eight acres of wetlands were located within the project boundary.

The Flambeau deposit existed at very shallow depth. Depth to bedrock at the mining site ranged from about 15 to 40 feet. Glacial sand, gravel and till overlaid Cambrian sandstone, which in turn sat above the weathered Precambrian metamorphic rocks containing the Flambeau deposit.

Mining of this shallow ore body was accomplished through a 35-acre open pit. The pit was oriented in a northeast-southwest direction and was 2,600 feet long, about 550 feet in width, and reached an ultimate depth of about 220 feet.

The first step in the mining process was to remove all topsoil from the mining site and place it into a stockpile for later use during site reclamation. Hydric, or wetland, soils were also removed and stockpiled separately in a pond while being kept saturated before use during wetland restoration. Glacial overburden, sandstone and weathered bedrock were then stripped from the pit area using scrapers and other excavating equipment.

Material was hauled out of the pit using 55-ton trucks and deposited in appropriate stockpiles. Once solid bedrock was reached, operators drilled and blasted the ore and waste rock prior to hauling. Ore was crushed on-site and shipped by rail to facilities in Canada for concentrating and smelting. The open pit mine operated two ten-hour shifts per day, five days per week. Material was removed at a rate of about 6,500 tons per day.

Over the course of the mining operation, about 1.9 million tons of ore containing about 9.5 percent copper and 0.175 ounces of gold per ton were mined and shipped from the site. The mine produced approximately 181,000 tons of marketable copper, 334,000 ounces of gold, and 3.3 million ounces of silver.

Waste material removed from the pit was directed to one of several stockpiles on the site. A separate stockpile was created for the glacial overburden, sandstone, weathered bedrock and low-sulfur waste rock containing less than 1 percent sulfur. These materials were stored in an unlined 40-acre facility just north of the open pit. High-sulfur waste rock and other material containing greater than 1 percent sulfur, which was capable of generating acidic drainage, was stored on a lined 27-acre stockpile area south of the pit. The high-sulfur stockpile was underlain with a plastic membrane liner and leachate collection system to prevent migration of potentially contaminated water from entering the groundwater system.

Groundwater flowing into the open pit was collected in sumps and pumped to lined holding ponds on the surface. Runoff from the ore stockpile/crusher area and waste rock piles as well as leachate from the high-sulfur waste rock storage facility was also directed to the same holding ponds. This water was then directed to a wastewater treatment facility and ultimately discharged to the Flambeau River upon meeting DNR state wastewater discharge permit limits. The water treatment facility used lime neutralization, sulfide precipitation and filtration as the main treatment technologies. Over the life of the mining operation, discharge from the treatment facility averaged about 300 gallons per minute.

During the active mining period, Kennecott employed approximately 70 employees, mostly from the Rusk County area.

Reclamation

Mine reclamation

View, looking southwest, of the Flambeau Mine during operations.
View, looking southwest, of the Flambeau Mine during operations.

The approved Reclamation Plan for the Flambeau Project specified that the open pit, upon completion of mining, would be completely backfilled with original rock and soil materials that were removed during mining and site preparation. Reclamation of the pit began in early 1997 and was completed in late 1998.

In accordance with the reclamation plan, stockpiled materials were backfilled according to their approximate pre-mining position. High-sulfur waste rock was blended with a prescribed amount of limestone for neutralization and placed into the pit first. The limestone served as a buffering material, and waste rock was sampled and tested prior to its removal from the stockpiles to determine the appropriate amount of limestone needed for neutralization of accumulated acidity and potential acidity which could be generated in the backfilled pit.

Following application of crushed limestone to the rock in the waste rock storage facility , the material was excavated, hauled to the pit, then placed in the pit and compacted. The high-sulfur waste rock was overlain by low-sulfur waste rock, weathered bedrock, sandstone and glacial till. The site was graded to the approximate pre-mining condition and long-term surface water drainage features were established. Topsoil was reapplied to the site and revegetation and wetland restoration efforts began.

The post-mining land use for the site was light recreation and wildlife habitat. To achieve that goal, the Reclamation Plan envisioned creation of diverse habitats on the site by reestablishing forested areas, various native grasslands and wetlands. The majority of revegetation activities at the site took place in 1998 and 1999. Grassland areas were seeded with a mixture of cover crop, native grasses and wildflowers. In addition, seeding in upland areas was supplemented with transplanting of live plant materials.

View, looking southwest, of the reclaimed Flambeau Mine.
View, looking southwest, of the reclaimed Flambeau Mine.

More than 7,000 plugs of wild strawberries, wild geranium, columbine and woodland sunflowers were planted in various upland areas. Woodland areas were planted with more than 2,500 tree and shrub seedlings and about 300 larger trees were transplanted from the on-site nursery established during initial site preparation. An 8.5-acre wetland area was constructed using wetland soils that were salvaged and stockpiled during site construction. During reclamation, this wetland was planted with more than 10,000 plants and bare rootstock of typical wetland species. Drainageways and biofilters were also planted with more than 17,000 live stakes of alder, willow and dogwood species.

In all, more than 170 different species of plants were seeded or installed on the mining site during the reclamation phase. The Flambeau Mining Company also established a trail system through the reclaimed site, which is now available for public use.

Monitoring

Environmental monitoring

Monitoring compliance with mine permit conditions required frequent on-site visits.
Monitoring compliance with mine permit conditions required frequent on-site visits.

Throughout the life of the Flambeau Mine, an extensive environmental monitoring program was conducted to ascertain the extent of environmental impacts from the project and to determine if the project was complying with all applicable statutory, rule and permit requirements. As specified in various permits, the Flambeau Mining Company was required to regularly monitor groundwater levels, groundwater quality, air quality, surface water quality, wastewater effluent quality and flow, mine inflow, wetlands, aquatic ecology, stockpile leachate quality and meteorology. Groundwater monitoring will continue at the site for several decades to measure conditions within and around the backfilled pit.

During active mining operations, monitoring was conducted and the results were submitted to the DNR and local governments. In addition, as part of its inspection/surveillance program, the DNR conducted periodic independent sampling to verify the results obtained by the company and also observed the monitoring procedures followed by the mining company staff and contractors.

Throughout the life of the project, the company has remained in substantial compliance with all permit conditions and applicable standards. Air monitoring indicated several exceedances of suspended particulate limits, only one of which was attributed to activities on the mining site: dust from a delivery of an uncovered load of crushed limestone. There were no exceedances of any effluent (treated wastewater) limits during the period of discharge. Monitoring of water quality and other characteristics in the Flambeau River similarly did not show any impacts from the effluent discharge. Anomalous results from some bioassay tests were reported, but in each case the company responded promptly and appropriately.

Groundwater monitoring

Monitoring results have indicated that groundwater levels have essentially returned to pre-mining conditions. Minor differences in groundwater elevations within the backfilled pit were expected because of the nature of the waste rock that was backfilled, as compared to the surrounding bedrock that was left in place.

On a volume per volume basis, the majority of the groundwater is flowing through the overlying till and very little water is moving through the bedrock and backfill material to the Flambeau River. Resaturation of the waste rock by groundwater infiltration is the primary mechanism by which oxidation of the remaining sulfides in the backfilled waste rock is controlled and the long-term environmental stability of the backfilled materials has been achieved. By maintaining the waste materials in a saturated condition, the potential for significant oxidation and ongoing acid generation is greatly reduced by limiting the availability of oxygen, one of the necessary elements for acid generating reactions.

Groundwater samples are collected from monitoring wells.
Groundwater monitoring wells at the Flambeau mine. Water quality within the backfilled pit will continue to be monitored in order to assess potential impacts to the Flambeau River.

Water quality within the backfilled pit will continue to be monitored to assess conditions in and around the backfilled pit and potential impacts to the Flambeau River.

The first few rounds of water samples collected from the wells installed in the backfilled pit in 1999 and for several years thereafter indicated elevated levels of sulfate, copper, manganese and iron were present. These results were not unexpected and were consistent with or slightly greater than the concentrations originally predicted during the permitting process. Since the initiation of groundwater monitoring of wells in the backfilled pit, results have been analyzed annually by comparing the results to predictions developed as part of the permitting process and additional more refined geochemical modeling predictions developed using actual data collected from the wells. These assessments have been summarized in annual reports submitted to the DNR. The most recent assessment suggests that due to ample availability of limestone and limited oxygen availability oxygen, there has been little to no input of oxidation products to the system over almost 20 years of saturation and the system is generally stable. Based on current water quality in the backfilled pit and geochemical modeling analyses of the backfilled pit, it is expected that water quality will continue to improve or remain at current levels and will not result in measurable impact to the Flambeau River.

In addition to the wells located within the backfilled pit, groundwater quality samples have been collected at wells surrounding the backfilled pit. Some of these wells recorded sharp increases in concentrations of copper, sulfate and/or manganese when mine pumping stopped in 1997.As with the in-pit wells, this was not unexpected. Recent data suggest levels for these parameters have steadily decreased since the wells have fully recovered and the concentrations have been generally either stable or decreasing since 2013.

Monitoring will continue at the reclaimed Flambeau Mine for many years. Monitoring results will continue to be compared to predictive analyses and modeling, and if substantial differences are observed to the extent that they may not comply with the permit conditions and applicable regulations, the company would be required to take action to prevent adverse impacts.

Vegetation monitoring

Results of vegetation monitoring conducted on the site from 1999 through 2002 indicated that the site was performing quite well. The site was stabilized, native species of vegetation were thriving and survival of the woody vegetation was greater than 80 percent. Grassland areas on the site were subjected to periodic controlled burns to further enhance native vegetation.

Based on this reclamation success, Flambeau Mining Company (FMC) asked the DNR to concur with its assessment that reclamation had progressed enough to warrant approval of a notice of completion (NOC) for the reclaimed Flambeau Mine. The DNR concurred with the NOC in March 2002 and established Nov. 1, 2001, as the effective date of the NOC.

FMC petitioned the DNR for a Certificate of Completion (COC) for the Flambeau Mine site in early 2007. After the DNR determined the site was still in compliance with the standards and criteria specified in the reclamation plan and mining permit and following a contested case hearing, FMC was issued a COC for the 149-acre portion of the mine site that contains the backfilled pit. As the result of a stipulated agreement between the parties at the hearing, the COC did not include the 32-acre Industrial Outlot that formerly contained the mine administration buildings, wastewater treatment plant, ore crushing and loading areas and a portion of the Type II Waste Rock Storage Area. With issuance of the partial COC, the portion of the site including the backfilled mine pit formally commenced a statutorily prescribed long-term care period which requires proof of owner financial responsibility for at least 40 years. FMC has posted a bond in the amount of $3.1 million to ensure completion of all required monitoring and maintenance activities during this period. Under current law, FMC, as owner of the facility, is responsible for the maintenance of the site in perpetuity.

Industrial outlot

Industrial outlot

On July 30, 1998, the DNR granted the Flambeau Mining Company (FMC) a modification of its mining permit to split the site into the main 149-acre mine site and a 32-acre Industrial Outlot to preserve the mine operations buildings and other facilities, rather than remove them as required in the approved Reclamation Plan. This change was made at the request of the Ladysmith Community Industrial Development Corporation, a local municipally-affiliated economic development entity, with the goal of preserving the facilities for use by another occupant in furtherance of local development efforts. The Industrial Outlot formerly held FMC's administration building, the wastewater treatment plant, water retention ponds, the ore crushing and loading area and rail spur as well as a portion of the Type II waste rock storage area. The Outlot currently houses the DNR's Ladysmith Service Center, Xcel Energy's power line maintenance shop and an equestrian trailhead facility. Under the stipulated agreement pertaining to the 2007 issuance of the certificate of completion (COC) for the majority of the mining site, FMC agreed to postpone applying for a COC for the Industrial Outlot until after 2010 and agreed to conduct additional monitoring, including five years of surface water monitoring.

Remedial actions and Stream C

Since the mine's closure, regular surface water monitoring and site inspections by FMC and DNR staff revealed that portions of the Industrial Outlot and an associated 0.9-acre biofilter (used to collect surface water runoff from the Outlot) had elevated levels of copper. In addition, an intermittent stream in that area, referred to as Stream C, exhibited elevated concentrations of copper as well as zinc. Since no baseline water quality data was collected on Stream C prior to development of the project, the exact source of the metals cannot be conclusively determined. FMC has taken a number of remediation steps since the elevated concentrations of copper and zinc were identified, including removal of mineralized rock and soil from the rail spur area, parking areas and staging areas on the reclaimed site as well as various efforts to modify and better manage surface water drainage on the site. The most recent activity initiated in 2015 included additional soil excavation, improvement of drainageways, modification of the drainage system and installation of permanent erosion control features in select areas. Subsequent surface water sampling indicates the water quality has generally improved. While the concentration of zinc no longer exceeds the water quality standard, the stream still exceeds the water quality standards for copper. Consequently, a portion of Stream C, by virtue of elevated copper concentrations, has been designated as an "impaired water" in accordance with section 303(d) of the Clean Water Act.

Related documents

Contact information
For information on the reclaimed Flambeau mine, contact:
Greg Pils