Reclaiming Surface Mines

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

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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