Appendix: How We Arrived at Our Numbers
As noted in the body of the report, very little public information exists on aggregate use in Ontario. The following methodology was used in deriving projected aggregate use in the GTA over the next 25 years and in deriving the landmass required to supply this aggregate.
Estimating the GTA’s Aggregate Use for the next 25 Years
Estimates as to how much aggregate will be required by the GTA over the next 25 years varies. According to industry sources, the GTA accounts for 40% of Ontario aggregate consumption[1]. Taking the average annual gravel use in Ontario from 2004-7 (175 million tonnes), calculating the GTA share (40%) and then multiplying by 25 years equals 1.75 billion tonnes.
The Ontario Stone, Sand and Gravel Association website[2] notes that projected aggregate use for Ontario over the next 25 years will be 4 billion tonnes. Again, assuming the 40% figure, this works out to 1.6 billion tonnes for the GTA.
To err on the side of caution we are estimating the GTA is on track to use about 1.5 billion tonnes over the next 25 years.
Estimating the Land Required to Mine the GTA’s Projected Aggregate Use
There is no publicly available method to easily calculate how much land is required to mine 1.5 billion tonnes of aggregate. Pit and quarry sizes vary as does the depth of a given pit or quarry. Indeed there is no accessible information that allows one to calculate the “average” pit or quarry.
The only clue about how much land is required to mine 1.5 billion tonnes of aggregate comes from a comment made by Ms. Carol Hochu, President of the Aggregate Producers Association of Ontario, to an Ontario Legislative Committee in 2000. Ms. Hochu stated:
- “If I could just paint a picture for you about what 150 million tonnes means, picture an area bounded by College, that is, the front of the Queen’s Park building, west over to Spadina, east over to Yonge and down to the waterfront. If you dug 60 feet into the ground in that whole area bounded by those roads, that represents about 150 million tonnes of aggregate product.”[3]
The area Ms. Hochu outlines in downtown Toronto is about 3.5 km2. In other words, 150 million tonnes of aggregate is equivalent to a 60 foot hole 3.5 km2. Therefore, 1.5 billion tonnes of aggregate is equivalent to a 60 foot hole 35 km2.
Using GIS and mapping technology, we have calculated the equivalent of a 60 foot deep 35 km2 and superimposed this on existing maps.
[1]Ontario Stone Sand and Gravel Association (OSSGA) Website http://www.theholestory.ca/inhtw.php .
[2] OSSGA http://www.theholestory.ca/index.php
[3] Standing Committee on Finance and Economic Affairs, February 16, 2000.Presentation by Ms. Carol Hochu, President of the Aggregate Producers Association of Ontario available at: www.ontla.on.ca/web/committee-proceedings/committee_transcripts_details.do?locale=en&Date=2000-02-16&ParlCommID=7&BillID=&Business=Pre-Budget+Consultations#P656_262200