British Columbia Mine Reclamation Symposia

Economic strategies for reclamation at Newmont Mines Limited, Similkameen Division Gould, Katherine L. 1988-12-31

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th  Proceedings of the 12 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1988. The Technical and Research Committee on Reclamation  139  ECONOMIC STRATEGIES FOR RECLAMATION AT NEWMONT MINES LIMITED, SIMILKAMEEN DIVISION  Katherine L. Gould M.Sc. Candidate, U.B.C. Resource Management Sciences  th  Proceedings of the 12 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1988. The Technical and Research Committee on Reclamation  140  ECONOMIC STRATEGIES FOR RECLAMATION AT NEWMONT MINES LIMITED, SIMILKAMEEN DIVISION  by Katherine L. Gould INTRODUCTION  Reclamation work at Newmont Mines Limited, Similkameen Division has focused primarily on waste rock dumps. A recent study of the spoil parameters governing reclamation success has indicated various management options which may enhance revegetation results. Costs associated with each of the reclamation options can be used in reclamation planning. This paper summarizes some research results and looks at possible economic strategies for waste dump reclamation. DESCRIPTION OF MINE AREA  Newmont Mines Limited, Similkameen Division is an open pit copper mine situated on the Similkameen River, 16 km south of Princeton, B.C.. The property lies between 900 and 1800 meters; within the Interior Douglas Fir and Ponderosa Pine Bunchgrass biogeoclimatic zones. The semi-arid climate provides an average of only 25 cm precipitation during the growing season. The steep canyon carved by the Similkameen River separates two areas of mining. Ore from both areas is essentially disseminated sulphide deposits, usually with less than 5% total sulfides. Copper mineralization is generally in the form of chalcopyrite-bornite with andésite the typical host rock. Glacial till and glacio-fluvial deposits covering the area range from 2 to 20 feet deep. Waste rock dumps account for 50% of the total land disturbance thus far. The main dumps are built up in tiers ranging from 30 to 60 meters high. The slopes are left at the angle of repose, which is usually about 37 degrees after they have been capped with the overburden till. Overburden is not usually applied to the large flat sites for revegetation purposes, however, some capping is done to ease transportation. No scarification of the flat areas has been attempted prior to revegetation. Reclamation of the dumps was initiated in 1972. The revegetation goal is to return disturbed sites to cattle and wildlife grazing areas. Approximately 130 ha of the dumps have been revegetated through aerial broadcast applications of fertilizer and agronomic grass/legume seed. Seed and fertilizer rates have varied over the years, however, they averaged 100 and 400 kg/ha, respectively. Older sites have received up to six applications of maintenance fertilizer. Early fertilizer mixes were a 6-3-1 ratio of N-P-K. COSTS  Excluding costs of overburden capping, the majority of reclamation dollars at Newmont have been spent on maintenance fertilization. Revegetation of a typical waste rock dump at Newmont can cost $1700/ha, of which 75% is attributed to fertilization (Figure :L).  th  Proceedings of the 12 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1988. The Technical and Research Committee on Reclamation  141  Figure 1.  DISTRIBUTION OF REGVETATION COSTS  Over the last decade many papers have presented results from variable fertilizing treatments in revegetation trials. Often the maximum fertilizer applications have resulted in the greatest biomass yield. Unfortunately, little reference has been made to the cost effectiveness of high fertilizer rates. Unlike the agricultural situation where maximization of fertilizer efficiency enhances profit, intense fertilization may not be the best investment of reclamation dollars. In a reclamation situation, inherent spoil parameters such as moisture may be limiting growth. Figure 2 illustrates the average biomass production on five of the older reclaimed sites at Newmont (revegetated earlier than 1979). Of the three fertilized flat areas, highest biomass production was achieved when 2000 kg/ha total fertilizer was applied. Although greater reclamation costs/ha were associated with the higher fertilization rate, there was no increase in the cost per kilogram forage produced (Table 1). Compared to the sites receiving 900 or 1500 kg/ha, intense fertilization appears justified if the reclamation goal is high forage production. Also illustrated in Figure 2 is the biomass production on one of the flat sites that has never been fertilized. This site is very productive due to the dense legume cover. Without fertilization, the cost of forage production is only 16 cents per kg. Unlike the other flat sites, however, this area had an even distribution of overburden cover deliberately applied  th  Proceedings of the 12 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1988. The Technical and Research Committee on Reclamation  142  th  Proceedings of the 12 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1988. The Technical and Research Committee on Reclamation  143  for revegetation. Even if overburden application costs 1 are included, forage production on this site may still cost only 55 cents per kg. Hence, overburden application to the flat sites in an attempt to establish a productive stand appears to be an alternative to heavy fertilization. Increased forage production through fertilization is less obvious on the overburden capped slopes. It is likely that moisture limitations on the slope faces override the fertilizer effects. As one would expect due to capping costs, the cost of producing forage on the slopes (>$1.00/kg) is greater than on the flat areas. REVEGETATION SUCCESS  Since 1972, many plant species and varieties have been used. Alfalfa is the most productive legume species, although sainfoin and cicer milkvetch are also dominant on certain sites. The abundance of crested and pubescent wheatgrass reflects the droughty characteristics of the spoil. Other grasses established include smooth brome, red fescue, and Canada bluegrass. An obvious variation exists within sites in terms of total vegetation cover and legume composition. This variation is evident on the slopes where species diversity, foliar cover, and legume establishment are greatest on the upper portions of the face. Further downslope, overburden thickness decreases and legume cover is replaced by sodgrasses. On the flat sites, high and low production areas are also easily identified. As these sites were treated from a fixed-wing aircraft, placement of seed may be contributing to the variability in cover. On the older sites that have been reseeded, or where natural reseeding has had time to occur, it is more likely that the variability in the spoil parameters have had a greater influence on revegetation success (Table 2). RESEARCH OBJECTIVES  A study was initiated in 1986 to identify the key spoil parameters which were inhibiting plant establishment and productivity. During the course of the study, it became apparent that cost is also an integral part of reclamation success. At Newmont, reseeding and refertilizing of unsuccessfully revegetated areas has dramatically increased reclamation costs. Therefore, the first goal of the study was to identify the reclamation methods most suitable to certain spoil types so that initial revegetation attempts would be successful. Secondly, with the recent fluctuations in metal prices, it was apparent that an economic evaluation of a variety of revegetation strategies would enable Newmont to devise a flexible reclamation plan, suitable for changing economic times.  1 Costs of overburden capping are presently being determined at Newmont. A conservative figure of $1000/ha has been used in these examples. Various references indicate topsoiling costs range from $1000/ha to $3500/ha depending on amount of material applied, methods, and equipment used.  th  Proceedings of the 12 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1988. The Technical and Research Committee on Reclamation  144  TABLE 2. GENERAL CHARACTERISTICS OF UNTREATED VASTE ROCK AND OVERBURDEN TILL  th  Proceedings of the 12 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1988. The Technical and Research Committee on Reclamation  145  RESEARCH RESULTS  Biomass production, measured in 1986, varied from almost zero to more than 4.5 tonnes/ha on many of the sites. It was assumed that a large proportion of the variability in revegetation success was due to nutrient deficiencies resulting from inadequate or poor placement of fertilizer. In an attempt to determine the effect of fertilizer placement on the variability of revegetation success, spoil was analyzed in both the high and low cover areas on selected sites. On all flats sites studied, areas with dense vegetation cover had significantly higher total soil nitrogen levels than areas with low vegetation cover (Figure 3). These differences were attributed more to legume input than fertilizer placement as the trend was also observed on the unfertilized site. Multiple fertilizer applications neither improved the uniformity of vegetation cover nor the distribution of N on the site. Grass cover and grass N content was positively correlated with soil N, which was highest on the site receiving the most N fertilizer. Percent legume cover and composition of stand decreased as N fertilizer increased. Alteration in grass/legume ratios as a result of N fertilization has been reported in other studies (Fleming 1973). On the slopes, soil N differences between vegetation types and sites were less significant. This may be for two reasons: 1) leaching of N from the legume areas on the upper portion of the face to the lower areas may be occurring, and 2) moisture limitations on the slopes may be overriding nutrient relationships to vegetation growth. Unlike N, soil and foliar phosphorus levels were not significantly different between high and low cover areas. Phosphorus content in alfalfa samples ranged between 0.20 and 0.23% (Figure 4), a level considered inadequate for rapid growth (Bickoff et. al. 1972). Higher applications of P fertilizer, however, have neither improved legume production nor foliar P content. These results are similar to other studies where there were moisture limitations (Fyles 1979, Righetti 1982). On the unfertilized site where available soil P is less than 5 ppm, successful growth of the legumes (dominated by cicer milkvetch) may indicate the existence of mycorrhizal fungi associations (Hayman 1986). Increased K fertilization did not significantly increase foliar K content in species sampled. Both legume and grass production, however, was positively correlated with soil exchangeable K. Although Mg has not yet been intentionally added to fertilizer mixes at Newmont, high soil Mg levels were also significantly correlated to dense legume cover. A 1976 study of the physical characteristics of Newmont waste rock dumps indicated that available water holding capacity and compaction would be limiting factors to plant growth on the flats (Morton 1976). Recent research data indicated a relationship between coarse fragment content (>2 mm) and vegetation type established. A positive correlation between grass cover and coarse fragment content was observed (Figure 5). On the slopes, percent cover and stand composition of grasses increased downslope as coarse  th  Proceedings of the 12 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1988. The Technical and Research Committee on Reclamation  146  th  Proceedings of the 12 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1988. The Technical and Research Committee on Reclamation  147  fragment content and moisture limitations increased. Above 85 percent coarse fragment content, grass cover also decreased (which usually occurs on the lower portion of the slope faces). On the flats, wheatgrass is usually established on the coarser materials with legumes on the finer overburden areas. Where the surface material is less than 60% coarse fragments and compacted (such as areas of overburden on the flats) total foliar cover is minimal. This is most likely a result of inhibited root penetration and a decrease in favorable microsites. Problems in spoil reclamation caused by compaction from heavy equipment have been observed in other studies (Omodt et al. 1975). RECLAMATION STRATEGIES  The research has indicated that the vegetation types generated on the waste dumps depend on both the physical and chemical characteristics of the spoil. Achieving the desired vegetation cover should be possible through the modification of these spoil parameters. For example, the results from the study suggest that legume production is positively influenced by available soil K, P, and Mg. Application of finer overburden material, if not excessively compacted, also appears to promote legume establishment. Therefore, if the reclamation goal is to provide a highly productive legume stand, then topsoiling, scarification, and fertilization with a P-K-Mg fertilizer mix would be suggested reclamation options.  th  Proceedings of the 12 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1988. The Technical and Research Committee on Reclamation  148  An alternative to intensive fertilization is illustrated by the one site that has never been fertilized. Modifying the physical characteristics of the site by applying overburden has resulted in a dense stand of cicer milkvetch. Achieving a dense stand of alfalfa without any P fertilization may not be possible. Cicer milkvetch has been shown to be more tolerant of some less desirable chemical and physical soil conditions than alfalfa (Hafenrichter et. al. 1968). Because of their nitrogen fixing ability, legumes may be desirable components for ensuring long-term stand stability. However, the Cu:Mo ratios in all legume species sampled were undesirably low for cattle use (less than 4:1). It may be necessary to promote grass growth in areas where heavy cattle use is expected. Both crested and pubescent wheatgrass had the highest Cu:Mo ratios of all species analyzed. Grass establishment has occurred on a wide range of spoil types at Newmont. Increased grass production does appear to result from higher N fertilization. Topsoiling of waste rock flats does not appear necessary. When overburden is applied, plant establishment and growth appear to be hindered if compaction occurs. Red fescue and Canada bluegrass have successfully established on some compacted overburden areas but biomass production is low. Results of the study indicated that overburden depth and coarse fragment content are more influential in slope revegetation than soil nutrient status. A uniform cover of overburden on the slopes appears necessary for a dominant cover of legumes and maximum biomass production. Although N fertilization appears to enhance grass growth on the flat sites, intense N applications to a coarse slope surface with moisture limitations would likely yield insignificant results. Application of costs to these reclamation alternatives is illustrated in Table 3. In this example four sites are considered for reclamation. Three management scenarios are developed. Although we have identified some of the key spoil parameters restricting growth on the waste dumps, amending them on every site may not be economically feasible. Alternative! 1 illustrates an attempt to achieve maximum forage production on all sites. Revegetation costs would total more than $180,000 for the 60 ha ($3000/ha). Site D is the most difficult to reclaim and the most costly due to the long slope requiring overburden capping. Alternative 2 is an effort to establish some level of forage cover on all sites for the minimum reclamation dollars possible. This option illustrates a 65% reduction in project costs - however, total forage yields are also likely to be low. Cost of forage production has increased from $0.81/kg to $1.38/kg. Although revegetation costs now total less than $1000/ha, retreatment of these sites at a later date may be required if vegetation cover is unsatisfactory. Alternative 3 is a compromised plan which attempts to suit both the mine's reclamation budget and the land use goals. Site D, an area that will not be  th  Proceedings of the 12 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1988. The Technical and Research Committee on Reclamation  149  th  Proceedings of the 12 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1988. The Technical and Research Committee on Reclamation  150  th  Proceedings of the 12 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1988. The Technical and Research Committee on Reclamation  151  grazed and would be difficult or costly to revegetate, is not treated. Instead, sites which are best suited to cattle use, or are highly visible, are selected as priorities for management input. Forage production is maximized and cost of production is lowest ($0.71/kg). Revegetation costs in this example are approximately $1700/ha. These scenarios illustrate the management dollars necessary to achieve maximum vegetation cover. Alternatively, during situations of economic constraint, achieving a satisfactory cover for the minimum $/ha could also be determined. Ongoing research is refining cost estimates and adding more information to this reclamation model. With the applicability to a wide range of site and spoil conditions, this model will be useful in future revegetation projects, and result in the best use of reclamation dollars. SUMMARY  In the past, Newmont has put extensive effort into their forage fertilization program. However, research has indicated that intense fertilization of all sites may not be the best financial approach for Newmont to undertake; there are other key spoil parameters which are influencing revegetation success. Determining the costs involved in overcoming these conditions has provided the needed information for future reclamation planning. Economic scenarios can now be developed from basic spoil analysis. These scenarios will aid in the development of a flexible and cost effective reclamation plan.  th  Proceedings of the 12 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1988. The Technical and Research Committee on Reclamation  152  REFERENCES:  Bickoff, E.M., G.0. Kohler, and D. Smith. 1972, Chemical composition of herbage. IN: Alfalfa Science and Technology. C.H. Hanson (éd.). Agronomy Series No. 15. Amer. Soc. of Agron. Madison, Wisconsin, pp. 247-282 Fleming, G.A. 1973. Mineral composition of herbage. IN: Chemistry and Biomchemistry of Herbage. Vol I. G.W. Butler and R.W. Bailey (eds.) Academic Press N.Y. pp. 529-566 Fyles, J.W. 1979. Maintenance fertilizer research at Kaiser Resources Ltd. IN: Reclamation of Lands Disturbed by Mining. Proc. 3rd Ann. B.C. Mine Reel. Symp. pp 325-334 Hafenrichter, A.L., J.L. Schwendiman, H.L. Harris, R.S. MacLauchlan, and H.W. Miller. 1968. Grasses and legumes for soil conservation in the Pacific Northwest and great basin states. LISDA Soil COns. Service, Handbook No. 339 Hayman, D. 1986. Mycorrhizae of nitrogen-fixing legumes. MIRCEN Journal, 2, 121-145. Morton, J.W. 1976. They Physical Limitations to Vegetation Establishment of Some Southern B.C. Mine Waste Materials. M.Sc. Diss. Univ. B.C., Vancouver B.C. Omodt, H.W., F.W. Schroer, and D.B. Patterson. 1975. The properties of important agricultural soils as criteria for mined land reclamation. Bulletin No. 492. North Dakota State University, Agric. Exp. Sta., Fargo, North Dakota. 52 pp. Righetti, T.L. 1982. Importance of soil nitrogen and phosphorus in semiarid reclamation. IN: Reclamation of Mined Lands in the Southwest. F. Aldon and W. Oaks (eds.) Albuquerque, New Mexico, pp. 80-86  

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