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A Source Deep in the Earth

BY PATRICK GARMOE
Daily Herald Staff Writer
Posted Sunday, September 03, 2006

When most people in the Fox Valley and western Lake County turn their faucets, they tap into a process that began decades before.

More than 100 years ago, water pouring out of suburban faucets this minute started its trek with a fall from the sky - in western Illinois, Wisconsin or even Minnesota.

After hitting Earth, the water seeps down, sometimes hundreds of feet below the surface, and then heads east.

Over months, years, even centuries it creeps toward Chicago's suburbs.

Water pressure and slopes in the Earth pull and push the water into aquifers, layers of rock filled with water.

In the suburbs, wells reach down into those aquifers and pump the water up to pipes, and then to homes from Lake in the Hills to Batavia.

This might sound strange to some, but it's not as odd as another popular myth.

Local engineer Larry Thomas sometimes still has to dispel the tale that the water around here somehow comes from Lake Superior.

No, it comes from Boone County. Sorry. It's just not quite as romantic said Thomas, chief operating officer for Crystal Lake engineering firm Baxter and Woodman.

Water stays hidden

The reality that water comes from rocky deposits deep in the Earth remains a mystery for many residents.

Northern Illinois homes sit above rock- and water-filled layers of ground called aquifers.

It's a firm surface. It's not hollow. It's not a river running underground. It's not a hollow underground lake you can put a boat in, said Al Wehrmann, director of the Center for Groundwater Science at the Illinois State Water Survey.

When rain falls onto the Earth, what doesn't end up in rivers slowly makes its way to the aquifers. The water then travels from west to east down an underground slope toward Lake Michigan or the Fox River.

In this area, there are two main types of aquifers from which we get drinking water.

Shallow aquifers are nearer to the surface - normally 30 to 400 feet down - and consist predominantly of sand and gravel deposits packed with water.

If one was opened, it would look like mud.

Beneath them, under 600- to 2,000-foot-thick layers of rock, lie deep aquifers.

The deep aquifers consist of large layers of limestone and sandstone. Water creeps through this porous stone at sometimes an inch to a few feet a year.

There are other deposits of water even farther down, but for now they largely remain untouched. The water is too salty or contains too many chemicals to be drinkable.

In southern Illinois, most deep aquifer water is too salty to use for drinking, which is why many communities outside of northern Illinois rely primarily on rivers or man-made lakes called reservoirs for water. Elgin and Aurora also use water from the Fox River.

Going deep

In this area, deep bedrock aquifers are far more favored than their shallow counterparts.

That's because in deep aquifers, the water is plentiful, easy to find and, normally with a little treatment, fine to drink.

“You can drill just about anywhere and hit water,” said Dave Kublank, Algonquin's chief water operator.

That's predominately thanks to the terrain.

Shallow aquifers are more like pockets of sand and gravel filled with water hidden among clay and other dry sediment. Deep aquifers meanwhile, are flat, thick and long.

Many can stretch over large swaths of the country.

The Ogallala aquifer, for example, stretches from southern South Dakota through Texas.

Therefore, there isn't a problem locating them, like there is with their shallow counterparts.

Although it's more expensive - drilling a deep well can cost $1 million, versus $650,000 for a shallow well - it's worth it, local water operators say.

Even when you do want to use them, shallow wells can prove elusive, or dry, as Campton Township residents have discovered in western Kane County.

“It's really limited around northern Illinois where you can get shallow water,” says John Dillon, Batavia's water superintendent. “You have to go out and really look for it.”

While water from deep aquifers in this area often must be treated for radium, the water they yield is typically better and more protected from chemicals than shallow aquifers, because they are farther from the surface.

And they typically can be depended upon to provide a steady flow of water for residents. The average house in the United States uses 350 gallons per day.

To provide that, a typical well around here will pump between 1,000 and 2,000 gallons a minute.

Because of the popularity of deep aquifers, the wells are pulling water out faster than rain water is replacing it. And that's where the worry lies.

“We're going to find the deep bedrock system is not going to be able to sustain the deep withdrawals it is presently sustaining,” says Scott Meyer, associate hydro-geologist with the Illinois State Water Survey in Champaign.

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