MINING IN KARST FORMATIONS

Environmental Hazards of Limestone Mining

OHIO KARST MAP

Potential Environmental Impacts of Quarrying Stone in Karst

  • A Literature Review

      • The influence of quarry size on environmental impact is obvious: all other things being equal, the larger the quarry, the larger the geomorphic impact. The size of quarries has increased over time, and so has their impact. (pg 8)
      • Poorly designed or poorly controlled blasts may cause rocks to be projected long distances from the blast site (flyrock), which can be a serious hazard. (pg 10)
      • The primary source of noise from extraction of aggregate and dimension stone is from earth-moving equipment, processing equipment, and blasting. The truck traffic that often accompanies aggregate mining can be a significant noise source. (pg 11)
      • Quarrying may intersect active ground-water conduits, or cause their blockage, with adverse consequences for aquatic communities. Ground-water withdrawal and diversion of surface water may cause above ground and underground hydrologic systems to dry up. (pg 13)
      • Karst systems have very low self-purification capabilities which makes karst water very susceptible to pollution. A major concern is that polluted materials, including pathogens, can be carried long distances without being filtered because of high flow velocities (several hundreds of thousands of meters per day). The sources of pollutants do not necessarily have to be man-made; there also are natural sources of pollution. Generally, karst occurs in areas that contain large amounts of organic material and bacteria, which can naturally degrade water quality. (pg 14)
      • Engineering activities associated with quarrying can directly change the course of surface water. Sinkholes created by quarrying can intercept surface water flow. Conversely, ground water being pumped from quarries changes streams from gaining streams to loosing streams and can drain other nearby surface water features such as ponds and wetlands. Similarly, blasting can modify groundwater flow, which ultimately can modify surface water flow. Discharging quarry water into nearby streams can increase flood recurrence intervals. (pg 15)

      • The major impact of quarrying in the karst saturated zone relates to quarry dewatering and the associated decline of the water table. (pg 15)
      • If a quarry intersects the watertable, ground water commonly will flow out of the rock into the quarry. Water may just trickle into the quarry or it may flow into the quarry at a rate of hundreds or thousands of liters per second. In some situations, it may be necessary to drain or pump the water from the quarry to protect people, quarry workings, and equipment. Pumping from a quarry will reduce hydraulic head and, thus, draw down water levels in the rock draining into the quarry. In the simplest case, the part of the water table impacted by quarry dewatering would look like a downward- pointing cone that has been depressed into the water table, thus its name cone of depression. If the quarry were the only major source of ground-water draw down in the area, it would be located over the apex of the cone of depression. (pg 16)