A new life for post-mining land: mine reclamation

Recla­ma­tion is a com­pre­hen­sive solu­tion to restora­tion and recon­struc­tion of land­scapes dis­turbed by min­ing activ­i­ties. Thus, recla­ma­tion should be defined as a set of works aimed at restor­ing the pro­duc­tiv­i­ty and eco­nom­ic val­ue of post-min­ing lands, as well as improv­ing envi­ron­men­tal con­di­tions.

Post-min­ing ter­ri­to­ries can be divid­ed into two groups:

• Land dam­aged by land­fills, spoil tips and waste rock dumps;
• Ter­ri­to­ries dam­aged by soil exca­va­tion, open-pit min­ing, extrac­tion of build­ing mate­ri­als and peat, dips and depres­sions at the site of under­ground min­ing oper­a­tions, trench­es built dur­ing the con­struc­tion of lin­ear struc­tures.

Depend­ing on the impact of indus­tri­al facil­i­ties and the degree of result­ing dis­tur­bances of the nat­ur­al land­scape, the recla­ma­tion tech­nol­o­gy is deter­mined with­in the spec­i­fied stages.

Reclamation of open-pit mining areas

The open min­ing method is rel­a­tive­ly cheap and high­ly pro­duc­tive. How­ev­er, it requires sig­nif­i­cant areas for con­struc­tion of quar­ries, waste dumps, rail­ways, high­ways, and indus­tri­al facil­i­ties. For exam­ple, con­struc­tion mate­r­i­al quar­ries require the area of 30 to 250 hectares, man­ganese ore or coal quar­ries — 1000 to 2000 hectares, iron ore quar­ries — 150 to 500 hectares. Usu­al­ly, ore pits are up to 250 meters deep, but their depth can reach 1,000 meters or more. The height of over­bur­den heaps usu­al­ly does not exceed 50 meters, while cal­cu­la­tions show that with a work­ing depth of 500 to 1000 meters, the area of the dump will exceed the area of the quar­ry by 4–7 times.

Quar­ries can be divid­ed into types depend­ing on their sur­face shape. They can be ter­raced, pit- or depres­sion-like. Accord­ing to the depth of the exca­va­tion, quar­ries are divid­ed into deep, medi­um and shal­low. Deep and medi­um-deep dis­used quar­ries are most suit­able for use as water reser­voirs, while shal­low pits may be suit­able for use as build­ing land or dis­pos­al of pro­duc­tion waste. Depend­ing on a num­ber of tech­ni­cal, eco­nom­ic and bio­log­i­cal fac­tors, the opti­mal method of recla­ma­tion is cho­sen for each spe­cif­ic deposit, the main tech­no­log­i­cal solu­tions of which are described in the devel­op­ment and recla­ma­tion project.

Reclamation of industrial mineral quarries

Indus­tri­al min­er­al quar­ries are con­struct­ed for the extrac­tion of phos­pho­rite, apatite, potas­si­um and rock salts, lime­stone, marl, clay, sand­stone, sul­fur, asbestos, mica, mar­ble, etc. Depend­ing on local ground­wa­ter lev­els, quar­ries can be dry or water­logged, which influ­ences the approach to their recla­ma­tion.

Recla­ma­tion of dry quar­ries is car­ried out in three stages:

• Sur­face shap­ing;
• Intro­duc­tion of a soil lay­er;
• Appli­ca­tion of nec­es­sary hydro­log­i­cal mea­sures and veg­e­ta­tion plant­i­ng.

Recla­ma­tion of water­logged quar­ries is car­ried out in two stages:

• Sur­face shap­ing;
• Flood­ing of the quar­ry.

Dis­used water­logged quar­ries are used as mul­ti-pur­pose water reser­voirs, dry quar­ries – as build­ing land, pas­tures, for­est plan­ta­tions etc. Before the over­bur­den exca­va­tion begins, the fer­tile lay­er of soil must be extract­ed and uti­lized in agri­cul­tur­al land devel­op­ment or oth­er recla­ma­tion projects, in accor­dance with the require­ments of the Land Code of Ukraine.

Stone quarries reclamation

Exploita­tion of stone deposits (gran­ite, migmatite, andesite) is usu­al­ly accom­pa­nied by sig­nif­i­cant destruc­tive changes of the land­scape, ero­sion, destruc­tion of nat­ur­al ecosys­tems, soil and water pol­lu­tion. The recla­ma­tion of such quar­ries involves restora­tion of nat­ur­al land­scapes, preser­va­tion and restora­tion of soil cov­er, plant­i­ng of trees and veg­e­ta­tion and cre­ation of water reser­voirs. Hard rock for­ma­tions are con­sid­ered unsuit­able for bio­log­i­cal recla­ma­tion due to their phys­i­cal prop­er­ties. Extract­ed over­bur­den, how­ev­er, can be sort­ed into fer­tile soil and hard rock mate­r­i­al.

Accord­ing to the extrac­tion con­di­tions, recla­ma­tion of stone quar­ries is car­ried out in the fol­low­ing order:

• Sur­face shap­ing;
• Back­fill­ing the quar­ry using the extract­ed over­bur­den and apply­ing a soft lay­er of soil at least 1 m thick;
• Veg­e­ta­tion plant­i­ng.

Reclamation of depleted peat deposits

Peat extrac­tion can lead to the degra­da­tion of marsh ecosys­tems, low­er­ing of the ground­wa­ter lev­el and loss of the soil’s water hold­ing capac­i­ty. Recla­ma­tion of such deposits includes restora­tion of hydro­log­ic regime, intro­duc­tion of appro­pri­ate veg­e­ta­tion, preser­va­tion of nat­ur­al con­di­tions for the repro­duc­tion of ani­mals, and mon­i­tor­ing changes in the prop­er­ties of peat itself. The pos­si­bil­i­ty of pro­duc­tive usage of post min­ing peat­lands depends on the method of peat extrac­tion pre­vi­ous­ly used, local hydro­log­ic regime, dura­tion of peat extrac­tion and the result­ing extent of envi­ron­men­tal dam­age.

Tech­ni­cal recla­ma­tion of deplet­ed peat deposits is usu­al­ly car­ried out in three stages:

• Land devel­op­ment works which include the con­struc­tion of drainage and irri­ga­tion sys­tems;
• Plan­ning works which include the con­struc­tion of roads;
• Veg­e­ta­tion clear­ing and tillage.

Bio­log­i­cal recla­ma­tion of deplet­ed peat deposits is car­ried out after the tech­ni­cal recla­ma­tion is com­plete. It includes:

• Ini­tial soil treat­ment;
• Selec­tion of plants for sow­ing;
• Intro­duc­tion of fer­til­iz­ers.

Reclamation of degraded landscapes due to geological exploration works

Dis­rup­tion of nat­ur­al land­scapes in the area where geo­log­i­cal explo­ration works are car­ried out is asso­ci­at­ed with the for­ma­tion of depres­sions as a result of open pit min­ing and the accu­mu­la­tion of rock mass on the sur­face. Waste rock dumps cre­at­ed dur­ing the explo­ration works can be tem­po­rary and per­ma­nent. Tem­po­rary ones are com­prised of rock mass exca­vat­ed dur­ing the con­struc­tion of explorato­ry trench­es and shal­low pits, and are lat­er used to back­fill the exca­va­tions. Rock mass extract­ed from oth­er explorato­ry exca­va­tions accu­mu­lates into per­ma­nent dumps, the biggest of which occur at the indus­tri­al sites of geo­log­i­cal explo­ration expe­di­tions which are engaged in the explo­ration of radioac­tive ores and deposits of crys­talline raw mate­ri­als.

Depend­ing on the con­di­tions and scale of explo­ration works, explorato­ry exca­va­tions can be done man­u­al­ly, using heavy machin­ery or blast­ing. Man­u­al exca­va­tions are the least harm­ful to the land­scape, while usage of heavy machin­ery often leads to exca­va­tion of explorato­ry trench­es of unnec­es­sary width, which incurs addi­tion­al expens­es.  Blast­ing is the fastest method, but also the most envi­ron­men­tal­ly harm­ful.

How­ev­er, regard­less of the used method of geo­log­i­cal explo­ration, all result­ing exca­va­tions and rock dumps must be recul­ti­vat­ed with the goal of restor­ing the land­scape to its orig­i­nal form as close­ly as pos­si­ble.

Reclamation of waste rock dumps

Accord­ing to their shape, waste rock dumps can be plateau-like, ter­raced or ridge-like. Recla­ma­tion and use of waste rock dumps large­ly depends on the way they were deposit­ed, their thick­ness and the physic­o­chem­i­cal prop­er­ties of waste rock. For exam­ple, low height plateau-shaped waste rock dumps can be recul­ti­vat­ed and used as arable land, hay­fields, pas­tures, plan­ta­tions and nature con­ser­va­tion areas.

Tech­ni­cal and bio­log­i­cal recla­ma­tion of waste rock dumps are car­ried out in the fol­low­ing order:  

• Removal and stor­age of the fer­tile soil lay­er pri­or to the cre­ation of a waste rock dump for lat­er use;
• Shap­ing of the dump slopes;
• Plan­ning works on the shaped sur­faces;
• Trans­porta­tion and appli­ca­tion of the fer­tile soil lay­er which was stored pri­or to the cre­ation of the dump;
• Con­struc­tion of pur­pose-built roads and basic land devel­op­ment;
• Con­struc­tion of hydrotech­ni­cal struc­tures, if need­ed;
• Seed sow­ing.

Land dis­tur­bance as a result of min­ing is sig­nif­i­cant both in terms of area and depth. Deplet­ed deposits form rugged ter­rain con­sist­ing of mounds and depres­sions, with unpro­duc­tive rock brought to the sur­face as a result. For exam­ple, in Kryvyi Rih, 62 mil­lion cubic meters of over­bur­den and 48 mil­lion cubic meters of ben­e­fi­ci­a­tion waste are dumped annu­al­ly. That is why the recla­ma­tion of dis­turbed land in Kryvyi Rih is car­ried out reg­u­lar­ly, both by sub­soil users and munic­i­pal ser­vices of the city: trees, shrubs, grass and oth­er veg­e­ta­tion are plant­ed on the waste rock dumps to improve the envi­ron­men­tal con­di­tion of dis­turbed lands.