Reclaimed Flambeau Mine

While there are other examples of successfully operated and reclaimed metal mines in Wisconsin, the Flambeau Mine near Ladysmith in Rusk County is the only example of a metallic mineral 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 completed by the end of 1999. As specified in the Reclamation Plan and Mining Permit the open-pit was backfilled. The backfilling process involved blending the stockpiled waste rock with a prescribed amount of limestone. Limestone, because of its neutralization capacity, was used to minimize the potential for the development of acid conditions prior to reflooding. Once reflooded, the threat of acidification is largely eliminated because, in effect, the concentration of dissolved oxygen is greatly reduced and not available to oxidize the waste rock and produce acidity.

The Wisconsin Department of Natural Resources gained valuable experience in its review and oversight of the Flambeau Mine, and will continue to acquire additional knowledge as monitoring of the reclaimed site continues for the next several decades.

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 over 100 additional holes were drilled into the deposit, delineating a nearly vertical, tabular shaped deposit averaging 50 feet wide, 2,400 feet long and extending to a depth of about 800 feet. The deposit contained over 50% sulfide minerals, primarily pyrite (iron sulfide), with economic 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. The Flambeau River is located at 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-1970's, 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 facility located a couple of miles to the south of the ore body. Upon completion of mining, the open pit would be allowed to fill with water and the remainder of the site would be revegetated. An Environmental Impact Statement was prepared and was found to be acceptable under the applicable laws at the time. During the final permitting hearing in late 1976, Rusk County indicated that it did not intend to grant the necessary zoning approvals due to various concerns it had regarding the mining project and the State's mining laws. As a result, the permitting process was terminated. Shortly thereafter, Kennecott put the project on hold due to poor economic conditions and uncertainty concerning the legal and regulatory requirements in the state.

The project remained in a state of dormancy until 1986 when Kennecott reevaluated the project and determined that a redesigned, scaled back project could be viable. This entailed the elimination of facilities such as a mill (mineral separation and concentration facility), tailings pond, and tailings disposal site. 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 to facilities in Canada for further processing (concentration and smelting), thereby avoiding the need for construction of a tailings disposal facility. In addition, the company proposed to completely fill the mined out 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, a subsidiary of Kennecott, formally restarted the permitting process for the project in 1987, kicking off a three year process of baseline data gathering, negotiations with local communities, and project design and review. The Department issued the Final Environmental Impact Statement for the project in March 1990 and the permit hearing was held during the summer, amid a high level of controversy. The independent hearing examiner issued all necessary permits in January 1991 and construction of the project site began in July 1991. Ore shipments from the site began in May 1993 and continued for just over 4 years. Backfilling of the pit took about 1.5 years and reclamation activities at the site were generally completed by the end of 1999.

Project Description

Haul trucks removed ore from the Flambeau Mine

The 181-acre mining site located about one mile south of Ladysmith is 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 8 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 sporadically occurring 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 trended 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 use during site reclamation. Hydric (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 haul trucks and deposited in appropriate stockpiles. Once competent bedrock was reached, it was necessary to drill and blast 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% 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 3,300,000 ounces of silver.

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 (saprolite) and low-sulfur waste rock containing less than 1% 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% sulfur, which was capable of generating acid 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. The ore stockpile, ore crusher and loading area were located adjacent to the high-sulfur waste rock stockpile and were also underlain by the plastic liner.

Groundwater flowing into the open pit was collected in sumps and pumped to 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 (retention basins). This water was then transported to a wastewater treatment facility and ultimately discharged to the Flambeau River upon meeting permit limits for selected constituents. 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.

Other facilities at the site included an administration building with a laboratory, ancillary support structures, a fuel storage area, a 1.6 mile railroad spur, a visitor center on top of the topsoil stockpile, a biofilter where the hydric soils were kept saturated, revegetation test plots and a temporary nursery. During the active mining period the mining operation employed approximately seventy employees, most of who were from the Rusk County area.

Reclamation of the Mining Site

The approved Reclamation Plan for the Flambeau Project specified that the open-pit, upon completion of mining, would be completely backfilled with original rock material that was separated from the ore (waste rock and glacial overburden). 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 pre-mining stratigraphic position. As such, high-sulfur waste rock was blended with a prescribed amount of limestone and placed into the pit first. Material was sampled and tested prior to its removal from the stockpiles to determine the appropriate amount of limestone (buffering material) that would be needed for neutralization of actual acidity and potential acidity in the backfilled pit.

Crushed limestone at the prescribed rate was added to the material before it was hauled to the pit. Backfill was then placed in the pit in three-foot thick lifts and compacted to specified requirements. The high-sulfur waste rock was overlain by low-sulfur waste rock, weathered bedrock (saprolite), sandstone and glacial till. The site was graded to approximate the pre-mining condition and provide for adequate surface drainage. Following rough grading, topsoil was reapplied to the site and revegetation efforts began, during which wetland restoration with the hydric soils was initiated.

This thumbnail image links to a larger version of this photograph of the Flambeau Mine during operations, view is toward the southwest.		This thumbnail image links to a larger version of this photograph of the reclaimed Flambeau Mine taken in July 2001, roughly three years after the pit was backfilled, view is toward the southwest.

The specified, 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 reestablishment of 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.

Over 7,000 plugs of wild strawberries, wild geranium, columbine and woodland sunflowers were planted in various upland areas. Woodland areas were planted with over 2,500 tree and shrub seedlings and about 300 larger trees were transplanted from the on-site nursery. 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 over 10,000 plants and bare rootstock of typical wetland species. Drainageways and biofilters (water retention and settling areas) were also planted with over 17,000 live stakes of alder, willow and dogwood species.

In all, over 170 different species of plants have been seeded or installed on the mining site during the reclamation phase. Flambeau Mining Company has also installed a trail system through the reclaimed site, which is now available for public use.

In 1998, the approved Reclamation Plan was modified to allow the plant site and a portion of the reclaimed high-sulfur waste rock stockpile area to be designated for an alternate land use. The Ladysmith Community Industrial Development Corporation approached the mining company and requested that the buildings and rail spur be left in place for use by another business. The Industrial Development Corporation has leased the property (32 acres) for future industrial use and must find a use for the facilities by the end of 2004 or the structures will be removed and the site will be reclaimed in a manner similar to the remainder of the mining site. Currently, the administration building is being leased by the DNR for use as the agency's Ladysmith Service Center and the water treatment building is being used for equipment storage by the DNR and a utility company. The Industrial Development Corporation hopes to find additional tenants for the property.

Vegetation Monitoring

The results of vegetation monitoring conducted on the site from 1999 through 2002 indicate that the site is performing quite well. The site is stabilized, native species of vegetation are starting to thrive, and survivorship of the woody vegetation is greater than 80%. Two deer exclosure areas (fences) have been temporarily established in order to protect two woodland areas from grazing impacts. These preventative measures will allow Department staff to monitor woodland species survivorship and provide a basis for comparison with grazed areas. Grassland areas on the site are subjected to periodic controlled burns to further enhance the native vegetation.

Based on this reclamation success Flambeau Mining Company requested the Department to concur with their assessment that reclamation had progressed enough to warrant a notice of completion (NOC) for the reclaimed Flambeau Mine. The NOC is an important milestone because it begins the 4-year evaluation period required to establish that reclamation success is sustainable.

Based on regular site inspections and review of Flambeau Mining Company’s 2001 Annual Reclamation Report, the Department accepted and concurred with the company’s notice of completion for the reclaimed Flambeau Mine. Ultimately, at least four years after the NOC issuance date, site reclamation will be reassessed in preparation for the certificate of completion (COC), which is the final test of whether or not the site is still in compliance with the standards specified in the Reclamation Plan and Mining Permit. At this point, a public hearing would be held, following which the Department may issue the certificate of completion of reclamation. Following certification, the reclamation bond (which is currently over $11 million) would be reduced to at least 20% of the original value. The reduced bond would be held for 20 years after the COC has been issued.

Environmental Monitoring

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

Throughout the life of the Flambeau Mine project 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, 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 characteristics including fish, macroinvertebrates and sediment, stockpile leachate quality and meteorology.

During active mining operations monitoring was conducted in accordance with specified procedures, and the results were submitted to the Department and local units of government. In addition, as part of its inspection/surveillance program, the Department conducted periodic independent sampling to verify the results obtained by the company. Groundwater monitoring will continue at the site for at least the next 40 years (from 2001) to determine conditions within and around the backfilled pit.

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 nearly returned to pre-mining conditions. Subtle differences in water table elevations exist between pre-mining and post-mining conditions near the southern portion of the backfilled pit. Comparison of groundwater levels for 2000, 2001 and 2002 suggest that this condition is becoming less pronounced. 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 water is flowing through the till and very little water is moving through the bedrock and backfill material. Resaturation of the waste rock by groundwater is the primary mechanism that is expected to control the long-term environmental stability of the backfilled materials. This is important because saturated conditions have been shown to minimize additional oxidation of sulfide minerals and ultimately the formation of acid drainage, which is a significant concern at many mining sites worldwide.

Groundwater samples are collected from monitoring wells located within the project boundary. The monitoring wells in this photograph are located at different elevations within the backfilled pit. Water quality within the backfilled pit will continue to be monitored in order to assess potential impacts to the Flambeau River.

The first few rounds of samples collected during 1999 from the wells installed within the backfilled waste rock indicated that elevated levels of sulfate, copper, manganese and iron were present. These results were not a surprise and were approximately equal to or slightly greater than the concentrations originally predicted during permitting and later updated prior to backfilling. Parameters that are highly sensitive to environmental conditions and geochemical reactions, including manganese and iron, are more difficult to accurately predict in the short-term. Analysis of data collected during 1999 thru 2002 suggests that for two wells (at one well nest) manganese and iron concentrations may be increasing, but are stable or decreasing elsewhere within the pit wells. Given the limited number of sample results available from monitoring wells within the backfilled pit, it is difficult to make any long-term predictions of how the site will perform. However, the monitoring results are consistent with the characteristics predicted during permitting and are not at levels that pose a threat to water quality in the Flambeau River.

In addition to the wells located within the backfilled pit, one well located between the pit and the Flambeau River has exhibited elevated concentrations of copper, sulfate, and manganese since mine pumping stopped. However, recent data suggests that these constituents are decreasing (copper concentrations are currently at the level of detection). This well was drilled within the mineralized bedrock just outside of the former pit boundary. During active mining, the surrounding mineralized rock was dewatered and the sulfide minerals underwent oxidation. Accordingly, it would be expected that metal concentrations would increase temporarily until the sulfide minerals were resaturated with groundwater and accumulated oxidation products are flushed from the system. This hypothesis was later confirmed by water quality data collected during mining. At the time it was not a significant concern because groundwater near this well was flowing into the pit where it was collected, treated and then discharged to the Flambeau River.

In a manner similar to the process described above, once the groundwater elevation recovers, and the initial flush of oxidation products is complete, groundwater quality in this well is expected to improve. In fact, sampling results since late 1999 indicate a significant decrease in copper (to the level of detection), sulfate and other parameters. However we cannot yet state whether it is a permanent trend given the limited number of sampling events. Nevertheless, the water quality sampled in this well is within the range of water quality expected by the analysis conducted during the permitting process, though concentrations of iron and manganese are slightly greater than predicted. However, water of this quality and rate of flow is not having a significant deleterious impact on the Flambeau River.

While these early monitoring results are important, it will be even more critical to review future results to verify that the concentrations of certain parameters decrease as was predicted. The observation of trends and long-term water quality sampled from wells within the backfilled pit will indicate whether the control measures, specifically limestone addition and reflooding, have been effective in minimizing the release of contaminants and additional oxidation of the sulfide minerals. We will continue to monitor the conditions at the reclaimed Flambeau Mine for many years to come. Monitoring results will be compared to predictive analyses and modeling, and if substantial differences are observed to the extent that noncompliance with the permit conditions and applicable regulations could occur, the company would be required to take action to prevent adverse impacts.