Gravel pit

Gravel pits are a main source of aggregates such as gravel and sand, which are extracted then processed extensively to be suitable for various uses. Aggregates are mined to make concrete, be crushed into construction aggregate, and for other industrial mineral uses. Gravel pits are located where there are rich sources of materials suitable to be crushed into aggregate, often at sites of fluvial, glacial, or floodplain geological deposits. Once a pit is dug into the aggregate, it can be lifted out by bulldozers that load it onto a conveyor or dredged out if the pit fills with water. It is then separated by particle size, crushed, and washed in preparation for use. All the layers of the road structure requires naturally occurring aggregates that are extracted from gravel pits or other surface material extraction sites. Beyond the initial construction of paved roads, gravel pits are important for the ongoing maintenance of unpaved roads because the surfaces of unpaved roads must be continually graded and re-surfaced with new loads of aggregate. In remote regions served by isolated unpaved roads, gravel pit operations are often located at strategic intervals every few hundred kilometers along the roadway in conjunction with road maintenance camps to provide the maintenance crews working out of these camps with the necessary materials. For example, along the Dempster Highway that stretches across the isolated northern region of Yukon Territory, Canada, there are several gravel pits in use for road maintenance and several more that have fallen into disuse. == Issues surrounding gravel pits ==

Environmental impacts Gravel pits disrupt the natural processes of the landscapes in which they are operating by displacing vegetation, soil, and rock. This in turn re-routes surface water flow changing runoff patterns, which can create further environmental problems for entire watersheds. Environmental impact assessments must be conducted before such projects to mitigate negative affects, and rehabilitation efforts should be undertaken after projects to restore the natural ecosystem. Unfortunately, most old gravel pits have not been rehabilitated after aggregate extraction has ceased, and their potential to be restored to accommodate improved ecosystem function is wasted. There are also concerns that agricultural plants coated in dust from gravel pit operations pose a risk to human health through consumption if the plant contains the dust. There have been widespread movements by communities affected by gravel pit operations to have them moved away to less windy, residential, or agricultural areas, and for better safety precautions to be adopted for worker health. == Rehabilitation potential of abandoned gravel pits ==

Once a gravel pit site is no longer producing aggregate it will often fall into disuse and be left abandoned. Many become informal recreation sites or transition into wetlands, lakes, or ponds as they fill with water, but remediation can help this process and reduce safety hazards they impose in their industrial state. Remediation programs can be undertaken to build abandoned gravel pits into sites of thriving wildlife habitats, parks or farmland, and/or be flooded and stocked for recreational fishing and to create aquatic ecosystems. ==Gallery==

File:John Linnell (1792-1882) - Kensington Gravel Pits - N05776 - National Gallery.jpg|Kensington Gravel Pits, an 1812 painting by John Linnell File:Aerial fg103 DSC 1469 Kiesgrube bei Geinsheim.JPG|A gravel pit in Germany File:Naturalizedgravelpit.JPG|A naturalized gravel pit, now Silver Springs Park in East St. Paul, Manitoba. Limestone processing plant, Tennessee.jpg|Tennessee quarry Image:Thornton Quarry.jpg|Overhead view of the Thornton Quarry. Image:Thornton Quarry2.jpg|Thornton Quarry with Interstate 80/Interstate 294/Tri-State Tollway above. File:Kongensbro gravel pit 2014-09-17 Diliff Reprocess.jpg|Panorama of a gravel pit near Ans, Denmark ==See also==