Quarry Rehabilitation and the Environment

Sand, gravel and crushed stone have to come from somewhere, and digging them changes the place they come from. What exactly changes, and what happens to the land afterwards? This page summarises how public bodies in the United States, England and Ontario (Canada) describe the environmental effects of aggregate extraction, what rehabilitation (also called reclamation or restoration) means, and why many jurisdictions require it to be planned from the start. For background on how the material is produced, see what aggregates are and how they are made.

01Environmental effects as public bodies describe them

The clearest short list comes from the English government's planning practice guidance for minerals. It tells mineral planning authorities (the local councils that decide quarry applications) to consider noise, dust, air quality, lighting, visual impact on the landscape, traffic, risk of contamination to land, soil resources, blast vibration, flood risk, land stability, and effects on designated wildlife sites and protected habitats and species. It adds that not every issue arises at every site to the same degree.

A Minnesota Department of Natural Resources handbook on sand and gravel pits (published in 1992 and updated in 2003) gives more detail on several of these. On dust, it separates plant-generated dust from drilling, crushing, conveying and screening from fugitive dust that comes off blasting, haul roads and stockpiles, and says fugitive dust is typically the largest contributor at a sand and gravel site. Water spraying, windbreaks, on-site speed limits and vegetative cover are among the controls it lists.

The same handbook raises water. Where mining reaches the water table, it says, pumping for dewatering or gravel washing can affect water levels in nearby wells, discharges can carry sediment to surface waters, and accidental fuel or solvent spills are a groundwater concern. It also warns that disturbed land may erode at rates as much as 1,000 times those of undisturbed land, and that sediment can damage fish spawning beds and clog streams. Wetlands are listed as a further concern, since digging can affect them.

Land use is a constraint on the industry as well. The US Geological Survey (USGS) says the reserves of construction sand and gravel are controlled largely by land use and environmental concerns, and that environmental regulations are among the reasons extraction is uneconomical in some places.

02What rehabilitation means

Rehabilitation is the work of returning a worked-out site to a safe, stable and useful condition. The English guidance describes the key stages: stripping and storing soils (or placing them directly on another part of the site), storing and replacing overburden (the rock and earth that lay above the deposit), shaping the final landform, then restoration proper, including soil placement and relief of compaction, followed by aftercare. Aftercare is a managed period after restoration in which, for example, new grassland or crops are established.

The Minnesota handbook stresses the same first step. Topsoil, subsoil and overburden should be stripped and stored separately, it says, and reserving topsoil is of great importance to eventual reclamation. It also recommends grading final slopes in gravel pits to a maximum steepness of 2.5 to 1, partly for safety and partly because steep, uneven ground inhibits plant establishment.

Timing matters. Both Ontario and England describe progressive or rolling restoration, where finished parts of a site are restored while extraction continues elsewhere. English guidance says planning conditions should seek this to minimise the area occupied at any one time, unless it would harm the standard of reclamation or be impractical.

03What a restored site can become

There is no single outcome, because the right choice depends on geology, groundwater, location and what the community wants. The English guidance lists new habitat and biodiversity, agriculture, forestry, recreation, waste management, and built development such as housing or industry among the possible afteruses.

Farmland. Natural England, the government's adviser on the natural environment, publishes a guide on returning mineral sites to agriculture. For arable use, it says the restored land needs at least about 1 metre of soil profile where possible, typically 0.3 metres of topsoil over 0.7 metres of subsoil, and good drainage.

Wetlands, lakes and wildlife. Pits that reach groundwater often fill with water. Ontario's Ministry of Natural Resources says rehabilitated sites in the province can become wetlands and wildlife habitat, farmland, parks, orchards, vineyards, golf courses and recreational fishing areas. The Minnesota handbook warns that ponds with rectangular shorelines, steep sides and uniform depth have limited value for fish and wildlife, and recommends irregular shorelines with bays, inlets and peninsulas. As an example it describes a 40-acre highway borrow pit in Hubbard County, Minnesota, excavated below the water table, which now holds eight small wetland basins and is expected to support a 12-acre wetland complex when vegetation is established.

Recreation and other uses. The Minnesota handbook says numerous depleted gravel pits in the state have been reclaimed to agricultural and forestry uses, fish and wildlife habitat, recreation areas or urban building sites, and that some have been so successful that they are no longer recognisable as former pits. It also notes that not every old pit needs reclaiming, since many have value in their present condition.

04Why many jurisdictions require restoration planning

The handbook explains the concern from the US side. It says nearly one million acres were affected by sand and gravel mining in the United States over a recent 40-year period, with less than a third reclaimed, and that unreclaimed pits can threaten public safety through vertical walls or deep water, cause erosion and downstream pollution, and attract dumping and trespass. These figures date from the early 1990s and should be read as historical.

The rules that followed differ by place. In England, the National Planning Policy Framework emphasises reclaiming minerals sites for an appropriate afteruse and carrying out restoration and aftercare to high environmental standards, according to Natural England. Responsibility lies with the minerals operator and, if the operator defaults, the landowner, and restoration is normally secured through planning conditions. A financial guarantee is described as justified only in exceptional cases. In Ontario, the Aggregate Resources Act requires a pit or quarry to be rehabilitated during its operating life, and the province runs a program for abandoned sites that stopped operating before licensing was required. Where you live, a different regulator may apply; see how quarries are regulated for the general picture.

Restoration also links to what happens next to the material itself. Some sites accept imported soil or recycled material as part of restoration, which connects to the discussion in recycled aggregates. In Ontario, imported excess soil must meet quality standards tied to the planned end use.

05The short version

Public bodies describe extraction as affecting dust, noise, water, soils, landscape and habitat for a limited period, and they treat rehabilitation as planned work with stages, from soil handling to aftercare. Outcomes range from farmland to wetlands and recreation. Rules and practice differ by country and site, and the reader's own regulator or a qualified professional has the final word.