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Quarries, such as this pit in Tamil Nadu, India, can be suitable storage places for city water supplies.
Quarries, such as this pit in Tamil Nadu, India, can be suitable storage places for city water supplies.

In my back yard - please!

This year Bill Langer has discussed some of the environmentally friendly uses of aggregate. This month he describes sustainable options for the use of the voids left behind after gravel is mined ...

Back in the early 1990s I was studying the gravels of Clear Creek around Golden, Colorado.

One beautiful autumn day I was looking at a residential lake development near Clear Creek that was built surrounding a water-filled reclaimed gravel pit. I was on the footpath, being mindful to not trespass or disturb the residents.

I was deeply engrossed in “framing” my camera for a picturesque photograph between the houses when I was startled (to put it mildly) by a loud voice from behind.

“Who are you, and what are you doing?”

“I am a geologist with the US Geological Survey, and I am studying residential lakes,” I replied.

"Some rock quarries also became suitable storage places for municipal water supplies."

That temporarily calmed down my accuser. I went on to say what a beautiful lake it was and how lucky they were to live there. That was met with a big smile. However, the smile turned upside down when I went on to say that it was a marvellous use for a reclaimed gravel pit.

“There is not a gravel pit in my backyard. It is a natural lake!”

To make a long story short, I finally defused the situation when I said the natural floodplain lakes around Golden often are created by floods and come and go at the whim of Mother Nature. Their lake, on the other hand, was well designed and would outlast what Mother Nature had in store for her own lakes.

Time travel backwards a decade. Water law is a serious issue in the arid to semi-arid west of the United States. Colorado and Nebraska have an agreement that Colorado will allow no less than a specified amount of water to flow along the South Platte River from Colorado to Nebraska.

The problem is most of the flow of the South Platte comes in the spring from the melting of the snowpack. Millions of gallons of water flow into Nebraska, far exceeding the amount required under the Colorado/Nebraska compact.

To remedy this, the Two Forks Dam was proposed to be built on the South Platte River, near Deckers, Colorado.

However, the permit to build the dam, which would have held enough to meet the annual needs of 400,000 people, was denied.

The water storage project at Glen Innes, NSW.
The water storage project at Glen Innes, NSW.

Now, fast-forward to the start of the 21st century. At about the time Two Forks was dying, state mining engineers decided mined-out gravel pits could be used as storage reservoirs. That decision changed the way aggregate companies and local municipalities looked at the pits. Not only could aggregate companies get the economic benefit from the gravel, but also they could turn the mined-out land into a water storage facility for the nearby communities.

Municipalities along the South Platte scrambled to permit new gravel operations, as long as they could purchase the hole. Gravel operators were happy to oblige because frequently the holes in the ground were worth more than the gravel that came out of them.

Some rock quarries also became suitable storage places for municipal water supplies.

One such pit is in Tamil Nadu, India. It is one of 22 inactive quarries storing rainwater reserves that are pumped via a 2.5km pipeline to the Indian city of Chennai. Another pit, in Glen Innes, New South Wales, has been enormously successful for the local council and residents, boosting the city’s water supply.

With the decline in the construction of new dams, this phenomenon has spread across the United States (and is also occurring in Australia). In some places, “Not in my back yard” has become “In my back yard, please!”











ABOUT THE AUTHOR
Bill Langer
Independent Research Geologist

Bill Langer is a freelance writer and retired Senior Research Geologist for the U.S. Geological Survey. Bill is now an independent researcher specialising in aggregate resources. Click here to email Bill or visit his website.








Thursday, 18 October, 2018 10:45pm
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