British Columbia Mine Reclamation Symposium

Properties of soils and their implications in the reclamation of lands disturbed by mining Christie, Paul A. 1980-02-17

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th  Proceedings of the 4 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1980. The Technical and Research Committee on Reclamation  PROPERTIES OF SOILS AND THEIR IMPLICATIONS IN THE RECLAMATION OF LANDS DISTURBED BY MINING  by Paul A. Christie, P.Ag. Soil Specialist Talisman Land Resource Consultants Vancouver, B.C.  23  th  Proceedings of the 4 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1980. The Technical and Research Committee on Reclamation  PROPERTIES OF SOILS AND THEIR IMPLICATIONS IN THE RECLAMATION OF LANDS DISTURBED BY MINING  INTRODUCTION Traditional  definitions  of  soil  often  involve  the  phrase  "natural  medium for the growth of land plants". The differing properties of soils  are  attributed  to  the  integrated  effect  of  climate  and  biological mechanisms acting upon geologic material as conditioned by relief over time. In the Canadian System of Soil Classification (1978) naturally occurring soils include those disturbed by activities such as cultivation and logging but do not include man-displaced materials such as gravel dumps and mine spoils. Natural soil extends from the surface to the depth at which soil forming processes can no longer be detected; therefore, a "non-soil" underlies unconsolidated material which has not undergone pedogenic processes. A more encompassing definition is given in the American System of Soil Classification "Soil Taxonomy" (1975), which states: "Soil...is the collection of natural bodies on the earth's surface, in places modified or even made by man, of earthy materials containing living matter and supporting or capable of supporting plants out of doors." This definition includes drastically disturbed materials such as mine waste deposits. I prefer this latter wider definition; however, in this paper soil includes that which occurs naturally as defined by the Canadian System and also the deeper surficial deposits not affected by soil forming processes.  I  believe  that  these  deeper  "non-soil"  deposits  often  provide the most economic medium for reclaiming lands disturbed by mining. My literature search indicated that research has been focused on the properties of mine waste materials and on the opportunities for  25  th  Proceedings of the 4 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1980. The Technical and Research Committee on Reclamation  reclaiming  these  lands  using  soil  amendments  and  various  leaching  processes. Much less information is available concerning the use of naturally occurring soil as a source of cover to aid the reclamation process.  It  seems  logical  to  me  to  use  naturally  occurring  soil  instead of trying to create a medium for plant growth from mine wastes in a fraction of the time it took Mother Nature to create soil. Recent legislation in some areas of North America stipulates that naturally occurring soil material in the area to be mined must be moved and stored  for  reclamation  of  the  mine  site.  The  limited  amount  of  information concerning this innovation suggests that positive results were  obtained,  however,  two  areas  of  concern  expressed  were  cost  effectiveness and contamination problems at the soil-spoil interface.  SOIL MAPPING A recent paper in Reclamation of Drastically Disturbed Lands states: "There  should  essential  to  inconceivable  be  an  engineering  success that  a  in  major  responsible  dictum  that  advance  disturbance engineer  planning  activities.  would  start  It  building  is is a  highway, an urban mall or a surface mine without some appraisal of the rock  and  soil  to  be  disturbed  or  used"  (Smith  and  Sobek,  1978).  Accordingly, for any mining project an up-to-date soil survey at a suitable level of detail should be incorporated into the planning process at the earliest stage possible. This soil survey will provide base data for the reclamation of disturbed lands and for ancillary developments such as energy and transportation corridors, plant sites and housing developments.  LEVEL OF DETAIL Soil  surveys  can  be  carried  out  at  three  levels  of  intensity.  Reconnaissance soil surveys a e regional in scope and the mapping scale is generally 1:50,000 (2 cm = 1 kilometre) or smaller. Semidetailed  26  th  Proceedings of the 4 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1980. The Technical and Research Committee on Reclamation  surveys are often still regional but can be effective during the early planning stages even for area specific purposes. The scale of semi-detailed surveys generally ranges from 1:20,000 to 1:40,000 (5 cm = 1 kilometre to 2.5 cm = 1 kilometre). Detailed soil surveys are used for site specific planning and are generally 1:10,000 (10 cm = 1 kilometre) or larger. The level of site inspection undertaken during these different soil surveys increases proportionately to the scale of the survey. Selection of an appropriate mapping scale and intensity of survey depends on the purposes of the survey. Generally speaking for such things as corridor selection for linear developments like road location, the map scale should be at least 1:25,000. For delineating bodies of soil suited to stockpiling for reclamation, a mapping scale of at least 1:10,000 is necessary. As a general guide one should keep in mind the area represented by a 1 cm square at a given mapping scale. At 1:50,000 a 1 cm square area covers 25 hectares and at 1:10,000 1 cm square covers 1 hectare.  MAPPING METHODOLOGY The first step in creating a soil map is to obtain the most recent aerial photographs available at a scale which approximates that of the  maps  to  be  produced.  The  aerial  photographs  are  pre-typed  through stereoscopic interpretation and by using any information on the geology and soils of the area. Pre-typing generally involves the delineation of the preliminary mapping units according to landforms and materials. The terrain classification system of the E.L.U.C. secretariat in 1976 can be used to pre-type aerial photos of B.C. landscapes.  Figure  1  shows  an  aerial  photograph  at  a  scale  of  1:20,000 which has been pre-typed and classified using the terrain classification system prior to field mapping. Note the use of wing points and correlation to the flightlines above and below. These are useful in the field and are time savers. Preliminary site locations are laid out according to the  27  th  Proceedings of the 4 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1980. The Technical and Research Committee on Reclamation  Figure 1 AERIAL PHOTUGRAPH (SCALE 1:20,000), PRE-TYPED AND CLASSIFIED  28  th  Proceedings of the 4 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1980. The Technical and Research Committee on Reclamation  mapping unit delineations on the photograph so as to arrive at representative sites at a reasonable level of field checking. The field program includes site location using the pre-typed photographs and whatever means of transportation is necessary. Site classification involves the description of environmental features including the terrain, vegetation and soil. The Resource Analysis Branch of the Ministry of the Environment has compiled complete site, soil profile and  vegetation  description  forms  in  their  Manual  for  Describing  Ecosystems in the Field (1980, in print). Soil pit excavation is a topic very dear to my heart considering all the layers of skin that I have removed over the years trying to bang down a soil pit in very unfavourable conditions. During most of my recent survey work attempts have been made to use a regular backhoe where access allows, or a climbing backhoe in more difficult terrain. It saves your hands and time, moreover, the end product gives much more detail as to the variability of the soil profile and its changes with depth. A tractor and power-auger is also adaptable where the terrain and soils are suitable. The amount of information obtainable using the power-auger is not as extensive as that using the backhoe because of the small pits and mixing of materials, however it is a useful method for checking variability of deposits. Considering that access to most of the potential mine areas in the province may limit excavation  to  the  hand  method,  it  is  essential  that  sufficient  manpower and time is made available to excavate pits of adequate size and depth so that soil variability with depth can be ascertained. Soil classification should be in accordance with the Canadian System of Soil Classification, 1978. Although much of the classification is Greek to most non-soils people, it is important information to the pedologist who must make sound interpretations. The selected mapping base depends on the preference of the users. Most engineers like planimetric maps with contours, whereas, many soils  29  th  Proceedings of the 4 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1980. The Technical and Research Committee on Reclamation  people choose a controlled photo mosaic or orthophoto compiled from the aerial photography. Mapping legends will depend on the users needs. For the base soil map, I prefer a fairly detailed and comprehensive legend followed  by  the  preparation  of  derivative  maps  which  present  suitability interpretations for various uses. No soil survey is complete without a sampling program and laboratory analyses. The sampling program design is important because samples must be representative of the various soil types in the project area. The analyses  should  meet  the  needs  and  objectives  of  the  survey.  The  pedology laboratory of the Department of Soil Science at U.B.C. has compiled a Methods Manual (1977) applicable to the B.C. situation. This laboratory as well as other private and governmental labs are able to carry out the analyses.  SOIL PROPERTIES Soils possess unique physical and chemical characteristics which influence their behaviour under varying conditions. Soils are generally separated into mineral and organic categories. The following discussion is general in scope and addresses only those soil properties important in mine waste reclamation.  MINERAL SOILS Mineral soils contain less than 30X organic matter by weight.  Physical Properties These soil properties affect both the engineering behaviour of the material as well as plant growth. The physical characteristics significant to the use of soils in mine waste reclamation are discussed  30  th  Proceedings of the 4 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1980. The Technical and Research Committee on Reclamation  under two headings:  "Inherent Characteristics" and "Behavioural  Characteristics".  Inherent Characteristics Particle  Size  Distribution  -  This  refers  to  the  grain  size  distribution of the whole soil including the coarse fragments. The Canadian System of Soil Classification (1978) uses the term texture to refer to the fine earth fraction (less than 2 mm) of the soil. The relative percentages of sand, silt and clay comprising the fine earth fraction are used to determine soil texture. Figure 2 depicts a soil texture triangle and shows the relative proportions of sand, silt and clay  in  the  various  textural  textural  classification  gravelly  or  cobbly  mapping  soils  at  is  to  the  groupings.  generally  indicate family  the  and  Using  modified coarse  series  this by  such  fragment  level  the  system,  soil  terms  as  content.  Canadian  For  System  establishes 11 particle size classes on the basis of coarse fragment size and content as well as on textural analysis. Bulk Density or Volume Weight - This is defined as the mass of dry soil per unit bulk volume and is probably the most important single factor  influencing  the  1975).  In  terms,  general  engineering soil  parameters  strength  of  soil  increases  (USDA,  with  SCS,  increased  density while permeability and compressibility generally decrease. The bulk density of a soil is increased by compaction and consolidation under heavy loads. Soil  Structure  separates  into  -  This  is  secondary  defined units  as  called  the  arrangement  peds.  These  of  peds  the are  soil often  arranged in a distinctive characteristic pattern in the soil profile. Soil  ped  classification  is  based  on  size,  shape  and  degree  of  distinctness according to the Canadian System of Soil Classification (1978). Soil structure is indicative of both physical and chemical characteristics  of  a  soil  and  influences  management  practices  in  varying degrees.  31  th  Proceedings of the 4 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1980. The Technical and Research Committee on Reclamation  Figure 2  Proportions of Soil Separates in Various Soil Textural Classes1)  1) SOIL TEXTURAL CLASSES ARE GROUPED AS FOLLOWS: Coarse textured  -  sand, loamy sand, sandy loam.  SEPARATE  DIAMETER (mm)  Sand  0.05  - 2.0  Medium textured -  very fine sandy loam, loam, silt loam, silt  Silt  0.002 - 0.05 <  Fine textured  sandy clay loam, clay loam, silty clay loam,  Clay  0.002  -  sandy clay, silty clay, clay,  32  th  Proceedings of the 4 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1980. The Technical and Research Committee on Reclamation  Behavioural Characteristics Many  soil  engineering  behavioural field  characteristics  manual  considered  characteristics of  the  most  USDA,  important  are  recognized  SCS,  (1975).  to  mine  in  Only  the those  reclamation  are  described below. Plasticity - This is the most important attribute of fine grained soils in terms of engineering behaviour. Soils with a high plasticity generally have a higher cohesion and resistance to surface erosion, piping, and cracking than soils with lower plasticity. The plastic limit is the water content corresponding to an arbitrary limit between the plastic and semi-solid states of consistency of the soil. This limit is determined by the water content at which a soil will just begin to crumble when rolled into a thread of approximately 1/8 inch in diameter. Liquid Limit - This is the second most important behavioral characteristic of fine grained soils. It is defined as the water content corresponding to an arbitrary limit between the liquid and plastic states of consistency of the soil. It is determined by the water content at which a pat of soil cut by a groove of standard dimensions will flow together for a distance of 1/2 inch under the impact of 25 blows in a standard liquid limit apparatus. Both clay and silty materials may have either high or low liquid limits. The  difference  between the liquid limit and the plastic limit is  termed the plasticity index, and it defines the range over which the soil exhibits plastic properties. The plasticity index is used to classify soils according to the unified system used by soil engineers. Available Water Storage Capacity - This is considered by most to represent that portion of water in the soil readily available for plant use. It is defined as the difference between the amount of water in the soil at field capacity and that in the soil at the permanent wilting point of most plants. Figure 3 gives an approximation of the  33  th  Proceedings of the 4 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1980. The Technical and Research Committee on Reclamation  Figure 3  Approximation of Available Water Storage Capacity  34  th  Proceedings of the 4 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1980. The Technical and Research Committee on Reclamation  available water storage capacity of soils according to texture and coarse fragment content. The important inference here is that medium textured soils (loam to silt loam) have the highest available water storage capacity, whereas, for fine textured soils (silty clay loam to clay), the available water storage capacity decreases with the degree of  fineness.  Similarly,  water  storage  capacity  decreases  with  in-  creasing coarse fragment (CF) content. Permeability - This is a soil property that allows the transmission of water and air. Permeability is measured as the rate at which water is transmitted  under  saturated  conditions  and  can  be  equated  with  saturated hydraulic conductivity. Permeability can be estimated from soil characteristics observed in the field such as texture, structure and soil pores. Generally, permeability increases as grain size increases and decreases as density increases. Consistence - This indicates the resistance of the soil peds to deformation  and is a factor of the degree of cohesion of the soil  particles. Consistence is described according to the moisture content of the soil under dry, moist and wet conditions. Consistence influences the  ease  of  excavation  as  well  as  handling  and  management  of  a  disturbed soil. Erosion - This is defined as the wearing away of the soil surface by water,  wind, ice and other processes. Soil susceptibility to both  surface and internal erosion (piping) is critical to the reclamation process. Generally, soils with a high susceptibility to surface erosion have a high susceptibility to internal piping. This is in contrast to low susceptibility soils which are generally more plastic and not as susceptible to surface or internal erosion. Many other important behavioural characteristics of concern to soil engineers should be considered in the use of soils for mine waste reclamation.  Basically  geotechnical,  they  include  compressibility,  shrink-swell and bearing capacity. 35  th  Proceedings of the 4 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1980. The Technical and Research Committee on Reclamation  Chemical Properties These soil characteristics affect both the engineering behaviour and plant growth. The following briefly discusses some of the more important chemical characteristics of mineral soils. Reaction - This is defined as the degree of acidity or alkalinity of the soil and is expressed in terms of pH. Descriptive classes for pH range from extremely acid at pH's less than 4.5 to very strongly alkaline at pH's greater than 9. Reaction influences soil corrosivity and  is  therefore  important  in  engineering  considerations  and  also  strongly influences plant growth. Plants generally have a narrow range of pH tolerance although some plant species are pH specific. Salinity - This is defined as the amount of soluble salts in the soil and  is  expressed  in  terms  of  electrical  conductivity  of  the  soil  saturation extract in mmhos per cm at 25° centigrade. Salinity affects the suitability of a soil for plant production as well as stability for construction purposes and corrosivity to metals and concrete. Cation Exchange Capacity (CEC) - This is defined as the total amount of exchangeable cations that a soil can absorb and is expressed in milliequivalents per 100 grams of soil. The cation exchange capacity of a soil is an index of its inherent nutrient holding capacity and is markedly influenced by organic matter content, the amounts and kinds of clay present, and, to a more limited extent, the pH of the soil. Generally, finer textured soils have a higher cation exchange capacity than coarse textured soils and, within a particular textural class, organic matter content and the amount and kind of clay present influences the CEC.  Fertility Status To ensure plant growth, an adequate supply of nutrients must be maintained in the soil medium. For reclamation purposes, the physical and chemical characteristics of soils discussed previously are adequate for  36  th  Proceedings of the 4 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1980. The Technical and Research Committee on Reclamation  the assessment of nutrient holding capacity. However, for successful plant growth, the availability and proportion of plant nutrients must be known for proper maintenance of the reclaimed area. Plant Nutrients - Plants obtain sixteen essential elements from the soil, three of which are commonly deficient and are therefore referred to as primary nutrients. These are nitrogen, phosphorus and potassium. Calcium, magnesium and sulphur are secondary nutrients which are less often deficient in soils. Plant growth in soil will be retarded if any of these elements are absent, insufficient or unbalanced with the supply of other nutrients. These elements are commonly supplied in the form of commercial fertilizers. Micro-nutrients or trace elements are those taken up by the plants in very small quantities. These include iron, manganese, copper, zinc, boron, molybdenum, chlorine and cobalt. They are just as essential to plant growth as the other nutrients, but arc required in much smaller amounts. Micro-nutrient uptake is often a problem in coarse textured soils, organic soils or soils having extreme reaction. Toxicities - Many of the micro-elements in excessive amounts may be toxic to plants. As an example, excessive copper has been shown to depress the uptake of iron by plants, which lead to symptoms of iron deficiency (Tisdale and Nelson, 1969). In B.C. soils other toxicities may arise due to relatively high levels of manganese, molybdenum, boron and selenium. Soil analysis should be carried out prior to the use of any material in mine reclamation. The analysis should include trace element detection particularly for any element expected to occur in relatively high amounts, based on knowledge of the regional geology and soil types.  37  th  Proceedings of the 4 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1980. The Technical and Research Committee on Reclamation  ORGANIC SOILS These  soils  are  recognized  at  the  order  level  prescribed  in  the  Canadian System of Soil Classification, They are described as soils derived dominantly from organic deposits and by definition contain more than 30% organic matter by weight. Most of the soils commonly referred to as peat, muck or bogs are included in the organic order. Such soils are usually water saturated during most of the year, occur in wet depressional areas, and are derived from hydrophytic vegetation. However there  are  exceptions,  some  organic  soils  comprise  organic  matter  accumulated on steeply sloping, well drained, forested sites. Under the Canadian System of Soil Classification organic soils are classified according to their degree of decomposition. For example, fibrisols are composed dominantly of relatively undecomposed fibric materials, mesisols are dominantly semi-decomposed mesic material; and humisols are dominantly well humified broken down organic materials. Organic soils often make poor construction materials, and they require specific  handling  if  used  in  the  reclamation  process.  I  wish  to  emphasize organic soils because of the tremendous number and variety of such deposits throughout B.C., particularly in mining areas. There is tremendous potential for utilizing these deposits as a soil amendment during reclamation, to increase the soil's cation exchange capacity and available moisture, to lower bulk density and help maintain desirable pH levels.  SOIL SUITABILITY FOR RECLAMATION  The suitability of soil for reclamation is determined from soil survey and analytical data. This determination should be carried out not only for soil in the area of the mine site, perhaps the most important area, but also for the surrounding environs. The approach described follows the Guide for Interpreting Engineering Uses of Soils USDA, SCS (1971).  38  th  Proceedings of the 4 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1980. The Technical and Research Committee on Reclamation  This  document  contains  a  guide  table  for  establishing  suitability  ratings of soils to be used as topsoil. In many parts of North America, particularly in the Great Plains area, this type of assessment would be adequate for determining whether or not a surface soil should be stockpiled for use during the reclamation. Most of the Prairies are relatively flat, have fairly homogeneous soils belonging to the Chernozemic (grassland) order, and have fairly deep topsoil layers composed essentially of mineral materials complexed with organic matter. However, in many B.C. mining areas, topsoil does not exist or, if it does, it is very shallow in depth and limited in extent. There are not many B.C. locations that I can think of where it would be feasible, especially in the economic sense, to strip  and  conserve  true  topsoil  material.  Undoubtedly  there  are  exceptions such as in parts of the Okanagan where a fairly extensive cover of Chernozemic soils exhibit some deep Ah horizons suitable for stockpiling. The approach that should be taken is to assess the surficial material, including the surface and subsurface unconsolidated soil material, to determine its usefulness for the reclamation of mine waste. For a specific location it might be feasible to stockpile topsoil; but for other locations where that is not feasible, it may be worthwhile to stockpile  surficial  deposits  that  have  the  characteristics  of  a  potentially suitable cover material. Table 1 is a modification of the topsoil suitability guide referred to earlier.  It  represents  an  attempt  to  identify  the  various  soil  characteristics which affect the use of the material for mine waste reclamation and to establish limits as to the degree of soil suitability for use as a cover material. This table is only a general guide and may or may not be applicable in specific mining areas. It certainly could be much more elaborate. For example, the textural classes used could be replaced by unified soil classes and other behavioural characteristics could be identified according to their type  39  th  Proceedings of the 4 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1980. The Technical and Research Committee on Reclamation  40  th  Proceedings of the 4 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1980. The Technical and Research Committee on Reclamation  and degree of limitation. Similarly, other factors such as available water holding capacity could be included. It should be noted that the table gives only estimates of the degree of soil suitability. Although it would be preferable to have a "good" soil material available, it may be that in some cases only soils rated "poor" in the table are available. Nevertheless, they are still suitable for reclamation, and despite their low degree of suitability, various soil amendments and management practices could be used to alleviate their limitations. Figure 4 represents a portion of a soil map compiled from the aerial photograph shown in Figure 1. This area was mapped at a scale of 1:20,000 and I have used it as an example of the type of information that might be presented from a soil survey during mine site planning. Seven mapping units and two sub-components were established. Table 2 shows a simplified legend that might accompany this type of map and indicates the characteristics of the mapping units and rates the soil in terms of its suitability as a source of cover material. Based on adequate soil survey information, an assessment of the surficial  material  at  the  mine  site  as  a  source  of  suitable  cover  material for mine waste reclamation, and the decision on whether or not to stockpile material can both be made. Also consideration should be  given  to  the  mapping  and  evaluation  of  all  suitable  materials  surrounding the mine site. They may be potential sources of mine waste cover material. This cover will provide a medium better suited to plant  growth  and  the  development  of  a  self-sustaining  vegetative  community than mine waste materials without such cover.  SUMMARY At the Second Annual British Columbia Mine Reclamation Symposium held in Vernon in 1978, J.U. MacUonald, the senior reclamation inspector for the B.C. Ministry of Energy, Mines and Petroleum Resources stated: "Reclamation in British Columbia cannot be defined by a set of regula-  41  th  Proceedings of the 4 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1980. The Technical and Research Committee on Reclamation  Figure 4 SOIL MAP COMPILED FROM AERIAL PHOTOGRAPH IN FIGURE 1  4 42  th  Proceedings of the 4 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1980. The Technical and Research Committee on Reclamation  43  th  Proceedings of the 4 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1980. The Technical and Research Committee on Reclamation  tions or legislation because of the extreme variances of physiography, biogeoclimatic zones and elevations. We have mines in the dry belt of the Okanagan, the rainbelt of the coast having 240 inches of rainfall a year, elevations of up to 7,000 feet and in nearly all cases little or no topsoil." I agree with the first part of his statement and, if by the term "topsoil" Mr. MacDonald means deep organic mineral horizons suitable for crop growth, I agree with the whole. However, if he is implying that there is very little if any soil suitable for use in reclamation present within the mine sites of B.C. then I take exception.  I have mapped soils ranging from the Canada/U.S.A. border north to Fort Nelson and from elevations at sea level all the way up to some 3,500 masl, and I think many of us would be surprised if we looked closely at the soil resources available. To support this statement I would like to refer to a soil transect on the Bel court property of Denison Mines that was mapped by Phil Christie during the soil survey he carried out for Denison this past summer. The Bel court property lies in the northeast coal block due south of Dawson Creek and due east of Prince George on the B.C./Alberta border at an elevation of between 900 and 2,000 masl. This potential coal property would be mined by an open pit process which would result in the removal of deep geologic strata as well as any overburden material as extensive pit areas are developed. The transect extended from the crest of a mountain ridge in the subalpine environment down to the upper mountain slopes within a potential mine site. On first appearance the entire ridge appeared to be composed of bedrock at or near the surface with only very shallow soil cover interspersed between bedrock outcrops. On closer inspection as revealed by the soil pit excavation at Site 1, the rocky material at the surface was in the form of stone stripes created by the intense subalpine environment and, in fact, there was a soil present that was deeper than expected. It should be noted that on photo interpretation and in the reconnaissance mapping process this ridge was determined to be predominantly bedrock at the  44  th  Proceedings of the 4 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1980. The Technical and Research Committee on Reclamation  surface. The texture of the soil material ranged from sandy loam near the surface to silty clay over bedrock at a depth between 60-75 cm. This Site 1 pit was located approximately 25 metres downslope from the ridge  crest.  A  soil  profile  obtained  at  the  Site  2  pit  located  approximately 25 metres further downslope showed that the soil depth increased to approximately 1 metre. Further soil pit sites along the transect showed a continuing increase of soil depth down the slope up to a depth of 3 metres in the forested area near the timber line. Much of the deposits in which these soils formed would be rated as fair according to Table 2. Within the proposed mine site area many other soil deposits occur which are also potentially suitable for use as cover  material  and  could  be  considered  for  stockpiling.  This  was  particularly evident near the mine site. Also an organic soil deposit was mapped in a depressional area in the vicinity of the ridge crest. Much of this organic material, again in the vicinity of the mine site, is potentially suitable for use as a soil amendment. In my view, to attain a  self-supporting vegetative community, the use  of existing natural soil  materials for covering mine wastes will prove  more practical than the using  fertilizers  and  expensive, continued support of plant growth irrigation  applied  directly  to  the  waste  material. In summation, I believe that by undertaking sufficiently detailed soil surveys and soil sampling programs we will be able to develop reclamation  programs  for  many  potential  mine  site  areas  throughout  the  province that will far surpass attempts at reclamation without this knowledge. I recognize that there are many important considerations not  considered  in  this  paper.  Such  topics  as  materials  handling,  stability of stockpiles and, maybe most important, the economic feasibility of utilizing soil material as a cover source have not been discussed. These are all matters that will have to be considered in any comprehensive reclamation program.  45  th  Proceedings of the 4 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1980. The Technical and Research Committee on Reclamation  REFERENCES Canada Soil Survey Committee, Subcommittee on Soil Classification. 1978.  The  Canadian  System  of  Soil  Classification.  Can.  Dep.  Agric. Publ. 1646. Supply and Services Canada, Ottawa, Ontario. 164 pp.  E.L.U.C. Secretariat. 1976. Terrain Classification System. Government of British Columbia, Victoria, B.C. 54 pp. Lavkulich, L.M. 1977. Methods Manual. Pedology Laboratory, Dept. of Soil Science, University of British Columbia, Vancouver, B.C. 224 pp. MacDonald, J.D. 1978. British Columbia Ministry of Mines and Petroleum Resources Reclamation Policy. In Reclamation of Lands Disturbed by Mining, Proc. of the Second Annual Mine Reclamation Symposium, Vernon, B.C. British Columbia Ministry of Mines and Petroleum Resources, pp. 69-79. R.A.B.,  Ministry  Ecosystems  of  in  the  the  Environment.  Field:  1980.  Definitions  of  Manual terms  for used  Describing on  field  description forms. In Print. Smith, R.M. and A.A. Sobek. 1978. Physical and Chemical Properties of Overburdens, Spoils, Wastes, and New Soils. In F.W. Shaller and P. Sutton (Co-eds.) Reclamation of Drastically Disturbed Lands. Amer. Soc. of Agronomy, Crop Science Soc. of Amer., and Soil Science Soc. of Amer., Madison, Wisconsin, U.S.A. pp. 149-169. Soil Conservation Service, U.S. Dept. of Agriculture. 1971. Guide for Interpreting Engineering Uses of Soils. SCS, Washington, D.C. 87 pp.  46  th  Proceedings of the 4 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1980. The Technical and Research Committee on Reclamation  Soil Conservation Service, U.S. Dept. of Agriculture. 1975. Engineering Field Manual. For Conservation Practices. SCS, Washington, D. C.  Soil  Survey  Staff,  Agriculture.  Soil  1975.  Conservation Soil  Service,  Taxonomy.  A  U.S.  Basic  Department  System  of  of  Soil  Classification for Making and Interpreting Soil Surveys. Agriculture Handbook No. 436, 754 pp. Tisdale, S.L. and W.L. Nelson. 1966. Soil Fertility and Fertilizers. The MacMillan Company. 694 pp.  47  th  Proceedings of the 4 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1980. The Technical and Research Committee on Reclamation  DISCUSSION RELATED TO P.A. CHRISTIE'S PAPER Questioner Unidentified: At what elevation were the soil pits? Answer: The transect ran from an elevation of 1700 metres at the ridge crest, then down to the timberline to a point 300 metres below it.  Questioner Unidentified: What was the average slope? Answer: About 15 degrees.  Bill  Herman  -  Pacific  Soils  Analysis  Inc.:  Some  of  the  problems  associated with vegetation, raised at the 1979 Seminar, resulted from toxicity levels of some of the elements - regardless of whether they were nutrients or not. I'm wondering if anyone has contemplated using organic amendments such as sawdust, as decomposing organic matter has a far greater buffering capacity than mineral soil per se? Answer: As your Ph.D was in organic soil chemistry, you could probably answer that question better than I. But it does point out why I stress the need for research into the use of organic materials. They are there, and we know that they have these ameliorative capacities. I think they are very important.  R. Hawes - B.C. Research: A major concern is to minimize the areas being disturbed during mining. If you look at the adjacent areas as a source of soils for reclamation, wouldn't you be increasing the area of potential disturbance. In your wetlands example, if you used those soils, would you not also be creating an additional impact on wildlife?  48  th  Proceedings of the 4 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1980. The Technical and Research Committee on Reclamation  Answer: The wetlands I mentioned were on the mine site and would be lost if the area is mined. I'm not suggesting that we should go out of the mine area and needlessly disturb organic deposits. A gentleman from Cassiar told me that they haul material from up to 20 miles away. Obviously, impacts are associated with the disturbance of natural sites, so it seems to me that if a source of cover material is not available, we're not going to go into the surrounding area to strip topsoil. Such action may well have a horrendous impact. Nevertheless, I have seen many bases where suitably deep unconsolidated surficial deposits do occur which could have been used. You must also consider the Soil Conservation Act and possible difficulties with lands in the Agricultural Land Reserve, but I still think the possibilities are good.  Niel Duncan - Energy Resources Conservation Board, Calgary: Is the comparability of soil material not important? There is a case on the Alberta plains where a lot of money was spent bringing in top-soil. It all washed away in a couple of years, which makes me think that compactability is an important factor. Answer: That is a significant point. I can only emphasize the need for analysis  of  these  materials.  Perhaps  mineralogy,  excavated  fraction analysis, and that sort of thing are also necessary. Other speakers may be stressing this, particularly Susan Ames who will be discussing the soil/spoil interface.  49  

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