Csanyi: Environmental hazards of limestone mining
Limestone deposits exist throughout the world. These alkaline, sedimentary rocks were laid down mostly as deposits on the beds of ancient seas. A valuable natural resource, limestone has many uses in construction, agriculture and industry. Limestone quarries can be above ground or underground, and can cover large areas. Environmental hazards from mining operations depend in part on the location, characteristics and extent of the mining operations.
Limestone mining can affect ground water conditions. Limestone deposits often occur in association with karst, a topography where limestone slowly dissolves away underground. The deposits result in sinkholes, caves and areas of rock fractures that form underground drainage areas. When mining occurs in karst, disruption to natural aquifers, or flows of underground water, can result. Often, mining operations remove ground water to expose the quarrying site, which can lower the water table and change how water flows through the rock formations.
Streams and rivers can be altered when mines pump excess water from a limestone quarry into downstream natural channels. This increases the danger of flooding, and any pollutants or changes in water quality affects the surface water. In Germany, salty water pumped from limestone quarries into rivers has degraded the water quality, according to the International Mine Water Association. Upstream surface water features, such as marshes, ponds and wetlands, can lose volume as their waters drain into the mine and are pumped out.
As water and rock are removed from mines, the support they give to underground features is gone. Sinkholes can develop, where the roofs of underground caverns are weakened or collapse. Collapse can be gradual or sudden. Although natural sinkholes develop over time, man-made ones predominate in mine areas. Sinkhole formation can cease after mine dewatering is stopped and the water table is allowed to return to normal levels.
Blasting and Construction
Limestone mines use two types of blasting. Small explosive charges set along drilled lines free blocks of stone to be removed for construction. Large charges reduce whole areas of limestone to rubble, which is removed for use as crushed stone. The noise, dust, and impact from explosions can result in noise pollution and dust. Underground forces from the blasts can cause sinkholes or change the drainage and water quality of underground aquifers. Construction equipment, such as large trucks, crushing machines and earth-moving equipment, also contribute to noise and dust.