Mineral Resources Division

Mining Task Force

The Aggregate Industry in Manitoba

What is Aggregate?

Each year millions of tonnes of aggregate are mined from literally hundreds of pit and quarry locations across Manitoba. Table 1 presents aggregate production in Manitoba from 1993 to 2000. Virtually everything we build requires aggregate materials, either as an engineered soil base for stability or in the form of concrete or asphalt products. Aggregate is used both in and under our roads, highways, streets, sidewalks, airports, railways, parking lots, sewers, foundations and in the buildings themselves. Other specialty uses include pre-cast concrete products, filtration in septic fields, backfill in underground mines, winter road sanding and armoring 'rip-rap’, which prevents erosion on shorelines and water courses. In spite of the enormous technological strides over the last century, there are still no economically viable substitutes for aggregate in the construction industry. Aggregate is a critical resource for the province, as important as water and electricity.

 

Table 1: Aggregate Production in Manitoba 1993 - 2000 (tonnes)

Aggregate consist of sorted sand, gravel and crushed stone material, valued largely for their physical strength characteristics when various size fractions are blended. This commodity is only available from two broad types of geologic formations.

The most common sources are fluvial-glacial landforms created during the last ice age where glacial melt waters sorted unconsolidated soil materials, washing away the fine silt and clay fractions and leaving coarser particles. Throughout Manitoba, thousands of "gravel pits" have been established in these unique physical features that include eskers, kames, and beach ridges. This coarse aggregate material can be readily excavated near the surface, usually by front-end loaders. Often the material is processed at the mine site by crushing any larger-sized rocks, and screening different particle sizes to blend a mixture with optimum support strength, or to meet a specific purpose such as concrete.

The other main source of aggregate is from outcrops of bedrock, or locations where the underlying bedrock is relatively close to the surface. Here the rock must be drilled and blasted in "quarries", then crushed down to a usable size. Due to the added cost of such processing, quarries are a more expensive source of aggregate than a typical gravel pit. The cost of stripping off any unconsolidated soils overlying the bedrock (called 'overburden') will also be a determining factor establishing the economic viability of a local bedrock location for mining purposes.

Where is Aggregate Mined?

Large volumes of aggregate are required whenever we build something in Manitoba, whether it is a railway, a highway, a power dam or a city. Furthermore, due to the high cost of transportation, we need a source for this aggregate that is as close as possible to the construction site. Aggregate is characterized as a high-bulk, low-value commodity. The cost of transportation often exceeds the in-situ value of the mineral itself.

For these reasons, we find literally thousands of pits and quarries spread throughout Manitoba, reflecting construction projects past and present. In any given year, just under a thousand or so locations may be actively mined however, a large proportion of the active locations change from year to year. Only where there is an ongoing demand for aggregate material, such as in the capital region, are local pits and quarries mined steadily. Elsewhere, mining activity in pits and quarries follows local construction activity. For example, sites may be mined one year to provide material for a nearby road upgrade. In subsequent years, these pits or quarries will sit inactive, awaiting the next major construction project in that locality. The aggregate industry is unique in that it is the largest mining sector in the province in terms of volumes produced and land acreage affected.

The other primary determinant on the location of aggregate mining activity is the availability of geologic sources, either as a fluvial-glacial deposit or as near-surface bedrock outcrops. In some parts of the province the geology is rich with such features however, in other regions there are no such local sources, and aggregate must be transported at great cost to meet local construction needs.

The specific nature of the material in a mineral deposit will also affect the pattern of use. In some locations a broad spectrum of particle sizes can be found, from fine sands to coarse stone, meeting the specifications for a wide range of aggregate products from concrete to road surfacing. In other locations the residual material may be suitable only for road base or must be combined with aggregate from a different source. Such sites would be less productive.

Within the capital region, we are fortunate to have two primary sources of aggregate. Historically, the city's aggregate was taken from the Birds Hill area, a complex glacial feature constituting an enormous gravel deposit immediately south of the provincial park. The second important source of aggregate is located in the Stonewall area, where near-surface limestone bedrock is being quarried. The proportion of aggregate supplied to Winnipeg from this source has been increasing annually, as the mineral reserves in the Birds Hill area are diminished.

What is the Value of the Aggregate Industry in Manitoba?

For the reasons explained above, the level of activity in aggregate mining is directly proportional to the level of construction activity in the province. Construction activity itself is tied to the overall strength of the provincial economy.

For example, in the year 2000, 445 aggregate producers in Manitoba reported production amounting to13 856 290 tonnes, extracted from 933 different locations. The value of Manitoba's aggregate production was rated by the Minerals and Mining Statistics Division of Natural Resources Canada to be in excess of $45 million, excluding the value of shipments to cement plants. The total number of employees categorized as directly employed by this industry in the year 2000 was 686, however, much of the mining was undertaken to support construction activity carried out by many of the same companies that mine the aggregate. Also associated with this industry are redi-mix concrete companies and a large number of independent truckers who make a livelihood hauling aggregate materials. A "rule of thumb" in the industry is that it takes 3 to 4 employees to produce 100 000 tonnes of aggregate product, and 5 to 6 employees to deliver that product to market.

Table 2 - Value of Gravel & Stone Production in Manitoba

Estimated by Minerals and Metals Sector, Natural Resources Canada

* Shipments of sand, gravel and stone to Canadian cement plants not included

How does the Aggregate Industry Work?

The aggregate mining industry is unique from other mining activity in several ways. A primary difference is that aggregate commodities are consumed almost exclusively within the province, and generally within relatively close proximity to the source. A very small quantity of gravel mined along the provincial boundaries is exported, largely balanced by imports in other border areas.

Secondly, the value of an aggregate deposit is influenced as much by the location relative to construction demands as it is by the quality of the mineral. This is unlike a gold or copper deposit. A 'perfect' gravel deposit in a remote and inaccessible location has no value, while a marginal quality bedrock outcrop close to the City of Winnipeg is worth a fortune to the owner.

Finally, the economic value of aggregate does not fluctuate based on an external world market, but on local supply and demand. As other sources of aggregate in the region are consumed, the value of residual materials increases. A mineral deposit that is uneconomic this year may be highly economic in five or ten years. That value can be instantly negated, however, if a new and closer source of aggregate is found during the interim.

Given the indispensability of aggregate, and the high cost of its transportation, construction companies are strongly motivated to explore for and to secure sources where future construction demand is anticipated. Larger companies do this on a systematic and long-term basis. In the highly competitive heavy construction industry, ownership of the only local source of aggregate may guarantee the lowest bid on a major public construction project, which is worth much more than the actual value of the mineral commodity itself. While government provides financial incentives to explore for other mineral commodities, market forces alone drive the highly competitive exploration for aggregate.

Since public projects such as road construction and maintenance require large quantities of aggregate, both municipal and provincial governments compete to secure supplies for current and future requirements. Many municipalities own gravel pits, and may even own the necessary excavation and processing equipment. Of the 446 reports of aggregate production in the year 2000, over 98 were from government agencies, primarily municipalities. The Department of Highways purchases and holds private sources of aggregate, and has an ongoing exploration program to identify new sources. On Crown land, the leasing rights over many known aggregate deposits have been withdrawn by the Mineral Resources Division at the recommendation of the Department of Highways, to ensure immediate availability to all construction contractors bidding on provincial highway projects.

What are the Social and Environmental Impacts?

Land Use Planning

One of the major dilemmas of the aggregate industry arises from the economic pressure to mine mineral sources as close to the market/population centres as possible. This often puts mining of aggregate, a heavy industrial activity, in direct competition with other land uses, in the 'public eye', and often in conflict with neighboring residential properties. Environmental standards governing the operation of pits and quarries are set out by regulation under The Mines & Minerals Act. In addition, the Mineral Resources Division has an ongoing program to identify high-potential mineral sources and to prevent their sterilization by other incompatible land use developments such as housing. Such conservation of known, high-quality sources of aggregate is established as a Provincial Land Use Policy under The Planning Act.

Pits and Quarries Rehabilitation

The legacy of mining in years past has been a proliferation of depleted pits and quarries, often highly visible to the public. Recognizing the unique, highly competitive and dynamic nature of the aggregate mining industry, the Mineral Resources Division, with close consultation and consensus from industry, implemented a unique rehabilitation program funded through an environmental levy on aggregate production. This approach spreads the cost of pit and quarry rehabilitation over the life a mine site in an even and equitable manner. Meanwhile, it provides assurance to the landowner, neighbors and the local municipality that the rehabilitation work will be done in the gravel pit or quarry once the mineral deposit is depleted.

Since its introduction in 1992, the Pit & Quarry Rehabilitation Program has been very successful. On the basis of aggregate production from private and Crown lands since the program’s inception in 1992, over $14 million has been collected. Expenditures on rehabilitation over that same period have exceeded $10 million. This work is overseen by the Mines Branch of the Mineral Resources Division and undertaken through the hire of necessary heavy equipment under contract. Over 1100 separate rehabilitation projects have been undertaken and over 4800 hectares (12,000 acres) of depleted surface-mined lands have been rehabilitated to a safe and environmentally productive condition. Many of these areas have been restored to agricultural use. Projects to reclaim degraded areas have also been undertaken within Wildlife Management Areas, Provincial Forests, and Provincial Parks.