Mining Foundations: Hard rock, sand, and gravel ground Alaska infrastructure.

Author:Simonelli, Isaac Stone

When it comes to mining, precious metals and rare earth elements get all the glory, pushing other resources out of the spotlight. However, in Alaska, as well as much of the rest of the world, gravel and sand go hand-in-hand with development. Aggregate is present in roads, landscaping, buildings, and nearly every other construction project.

"It's in everything as far as the building goes... aggregate is in everything," explains Ryan Zins of Anchorage Sand & Gravel. "So we mine it, we process it, and we sell it as a construction material for homes, for parking lots, for roads. It's used in ready-mix concrete for sidewalks, foundations, parking garages... it's extremely important. The state would be kind of at a standstill if you didn't have aggregates."

Aggregates is a sweeping term in the construction and mining industries that describes any sand- and gravel-based product.

Though aggregate is found on every construction site in Alaska, the biggest buyers are the Department of Transportation and municipalities, says Zins.

"However, it depends where you're at. Anchorage has a lot of peat and marginal soils, so a lot of the land is not suitable for building here," Zins says. "Unless you have good foundation--[and] you build on top of peat or a bog--it's gonna sink or not settle uniformly. So your second floor may become your first."

In 2001. the Alaska Division of Geological and Geophysical Surveys identified 125 companies producing aggregate in the state. Though Anchorage Sand & Gravel was not listed among them, the company has been operating in the Last Frontier for more than eighty-two years.

"We originally had operations down on First Avenue and mines all throughout the Anchorage bowl," Zins says. "Most of the time you're just looking for good aggregate."

Quality aggregate will often be a harder, quartz-heavy rock with nice gradations with a limited amount of clay or organics in the mix, explains City and Borough of Juneau Lands and Resources Manager Greg Chaney, noting that the City and Borough of Juneau has a couple of rock sources.

"Sand and gravel has to be well sorted. It can't have contaminants--the contaminants can either primarily be silt or clay," Chaney says. "That kind of stuff makes it frost susceptible: water can soak in and it freezes and then it expands."

Well-sorted sand and gravel, however. tends to drain more naturally, making it less susceptible to frost heaving.

"The other big component is the hardness of the material...

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