Reclaiming Surface Mines ©2007 Dr. B. C. Paul

Mines That Can Be Concurrently Reclaimed  Area Strip Mines and Most Contour Strip Mines can be reclaimed as they are being mined –The sequence removes overburden from one side of the pit and fills the backside of the pit  Most common reclamation is to carefully recover topsoil and subsoil on the Highwall side and then place it back in sequence over the spoil used to backfill the pit  Following placing the topsoil back you replant

Variations  Draglines build peaks and valleys behind them –You can accept the peaks and valleys and reclaim as hills and valleys – often good for forest reclamation (currently almost illegal) –You can fill inbetween the peaks and valleys by dumping trucked overburden to fill the valleys.  Then you have flatland (good for grass-land reclamation) –You can put dozers on the peaks and push them into the valleys to level things  Then you have flatlands

Placing Topsoil Above Overburden  Bucketwheel Excavators can stack unconsolidated fairly smoothly over more rock overburden. –Dozers are still a favorite for leveling things out –Technique can also be used with conveyors moving material  Topsoil layers movement –Can push off with a dozer, load into trucks, tailgate dump and smooth with dozers –Can pick up with scraper and set down in layers as thin as 6 inches –Some real creative techniques like building dikes, slurrying in soil and letting it settle into place

Anomalies  Strip Mines will always stop eventually. –There may be no material to fill the “final strip cut”  Popular Technique is to reclaim as a lake –Make popular fishing holes  Issues – on the highwall side it may be a steep drop into the water (drowning or falling risk)  May need to blast or smooth down the highwall –Can set up as shallow waters – makes great wetlands – fine duck habitat and hunting haven

Other Anomalies  If mining off a Mountain Top restoring a steep contour could be very erosion prone –Can use flatland reclamation layers –This yields a mountain with a flat top  Can be very good environmentally –People like to build on flatter land  This is usually in the valleys – this is right by the streams and in the areas of most sensitive wildlife habitat  Giving them prime flatland out of the river valleys cuts flooding risk and a host of environmental issues  Can also aggravate the vista people, your sticking unnatural flat top mountains in peoples views

Non-Concurrent Backfilling  To backfill one side of the pit while mining the other slope has to be slight enough that the stacked overburden does not slide back into the pit. –Steeply dipping beds or stocks obviously don’t meet this safety limit  Can in theory stack material and then put it back in when you are done –Not usually feasible –Would disturb large areas with stacked material –Rehandle costs would not be affordable at natural resource prices the economy depends on  Better alternative with series of small pits is to haul from one pit and then dump back into another older pit –Often done with dipping bed open pit mines such as coal or some phosphate in Idaho and Utah

Sometimes Filling the Pit Does Not Make Sense  Typical Examples –Quarries – most of the material extracted was rock for building – there is no fill  Some have looked at putting demolition and other waste materials in to fill but this generally has its own environmental concerns –Large Metal Open Pits  Holes a 2,000 ft deep and several miles wide that took 70 years to dig out are not realistically feasible to fill.  Solutions often involve graded slopes and lakes

Quarry Reclamation  Graded slopes and lakes have made a number of old quarries into resort communities  Some areas around Chicago have used quarries as storm water storage sumps –They need to treat storm water but building plants to treat storm surge makes little sense – store and process slow and steady