Drilling into history: Search for new Fayette water source unveils region's glacial past 2002.12.04

drill_big.jpgBy DAVID GREEN

All water is old water, says Joyce Dunkin. It just gets recycled—over and over and over.

Dunkin, a geologist with Limno-Tech Environmental Engineering, is kneeling over a display of core samples collected by well drillers. They’ve brought to the Earth’s surface an array of sand, silt and gravel that hasn’t seen the light of day for tens of thousands of years.

Dunkin is part of a team working to establish a new well field for Fayette’s municipal water system. Drillers are punching into the ground on the Brawley property north of town, searching for a good aquifer—a water-bearing area of gravel deep beneath the Earth’s surface.

It’s not that water is scarce—it’s literally everywhere underfoot—but finding a source that’s adequate to supply a community of 1,350 isn’t always easy. Fayette, in the water-rich northwest section of Fulton County, is the only municipality in the county to fill all of its water needs from a well.

There’s no problem with the volume of water rising from Fayette’s existing wells, but traces of vinyl chloride—linked by the Ohio EPA to the former Fayette Tubular Products factory—have some citizens on edge. Testing shows the  incidence of the contaminant is minute, but village officials want a new source of water established in case the situation worsens.

The first core Dunkin examines is dry, since the water table has not yet been reached. All of this soil—right down to the bedrock more than 200 feet below—is a product of the glaciers that once covered this part of the globe.

The core from nine to 19 feet is brought to Dunkin. It’s sandy, but there’s moisture, and ground water is pegged at 15 feet down. Next comes a darker, tightly-packed soil that Dunkin refers to as silt. Most anyone else would call it clay. The distinction, she says, comes in the size of the grain.

A substance with grains larger than 2 mm is referred to as gravel. Sands vary from 1/16 to 2 mm. Silt particles measure in the 1/256 to 1/16 range, and clay has the finest grain of all.

Although not as tight as clay, silt can serve as a good “confining layer” to seal the water below and keep it under pressure.

A few rocks showed up in the layer of sand at 28 feet—likely visitors from Canada. The bedrock underneath Fulton County is topped by shale that formed from ancient seas, but what the glaciers pushed south is much, much older. The rock making up what’s known as the Canadian Shield is among the oldest on the planet and it wasn’t until millions of years later that the glaciers scooped up pieces and slowly brought it south.

“You never know what you’re going to bring up in these cores,” said George Stuckey, a geologist with the Ohio EPA’s Drinking and Ground Waters Division. “You can find anything in this glacial melt.”

The advancing sheets of ice scoured the landscape, pushing rocks and soil ahead of them and locking up vast amounts of debris in the ice as the glacier grew. Up to 30 percent of a glacier’s mass consists of rock and soil, Stuckey said.

A very uniform gray sand appears at 29 feet. The presence of sand suggests glacial outwash—a natural sorting of gravel and sand that was carried away from the edge of the melting ice as temperatures warmed.

“We’re probably the first humans to see this,” Stuckey says as Dunkin pokes through the sample.

The drillers soon deliver another 10-foot section to the viewing area and a gray, moist gravel shows up at the 48-foot depth.

“I see we’re starting to get into the good stuff,” says a driller.

Gravel is good. Water moves around gravel easily, much more easily than through sand. And forget about silt. There may be water present, but it’s hardly suitable for pumping out through a well shaft.

Dunkin likens a gravel aquifer to a glass of crushed ice. Stick in a drinking straw—a miniature version of a well—and the water rises with little effort.

The gravel section—extending down through 61 feet—proves to be the first of four confined saturated zones. This one appears to correlate with the existing village well field.

Stuckey finds a piece of fossilized coral at around 80 feet. Who knows, he says, it could have been pushed down from Petoskey or Rogers City.

Dunkin is asked how far back in history the various depths represent, as though each foot down belongs to a particular moment of the geological past. She explains there’s no clear answer to that question.

“It gets really tricky to age date glacial till,” she said. “Some of the older glacial deposits may have been scoured away.”

Scientists are aware of four glacial eras, starting with the Nebraskan as far back as two and a half million years. The Kansan had an estimated starting date of 750,000 years ago, followed by the Illinoian which lasted from around 500,000 to 125,000 years back.

The Wisconsinan, the most recent to date, advanced from the north about 70,000 years ago and retreated from this area perhaps 14,000 years back. The ice covering Fulton County was likely at least 4,000 feet thick.

The Wisconsinan glacial period was responsible for most land forms in this area, but to sort out what’s what among the 200 some feet of till isn’t so simple. It wasn’t 50,000 years of solid ice. The Wisconsinan period alone featured at least 16 separate stages of advance and retreat.

“It’s pretty complex geology when you get into glacial territory,” Dunkin said.

Streams would form under the ice and carry sediment in a different manner from the main melt. A moraine would form at the edge of glacier, but then a later advance of ice pushed debris farther on.

“In general, the deeper it is, the older it is,” Stuckey says, “but a lot of it was reworked and mixed. What you see in the bore hole is only partial. A lot was washed away by melt water.”

The samples are beginning to show greater variation. Sand and gravel for four feet. One foot of dry clay. Seven feet of silt with gravel. One foot of wet sand.

Wet, then dry, wet, then dry, right down to 135 feet where a wet sand and gravel layer begins.

This extends another 60 feet before returning to sand. This looks good. The layer represents an ancient outwash plain. As a glacier melted, the gravel was dumped in this area while much of the sand was carried farther away in streams pouring off the face of the ice wall.

The hole is extended to 206 feet before quitting. Dunkin expected to strike bedrock by then, but it never happened. Glacial sediment could measure up to 300 feet thick in this area of the county—even deeper where it filled in long lost river valleys—but Dunkin has records of bedrock depth from only four other township wells.

The drillers figure they have what they came for: a large, high producing aquifer to serve the village.

Aquifers—underground rivers of fresh water flowing to destinations unknown….

Hold on a moment. True, it’s underground, and yes, there’s movement, but drop the image of a river.

“That’s a big misconception that people have about ground water,” Stuckey said.

Except in extreme cases, perhaps in limestone terrain, you might have a stream of water.

“Generally, ground water flow is just movement around sand grains,” he said.

Ground water flows from an area of higher pressure (such as a hilltop) to an area of lower pressure, explains University of Toledo associate professor of geology Mark Camp. Flow is dictated by several parameters, such as the material that’s holding the water (sand vs. gravel vs. silt), climatic conditions and dissection by streams.

“Some moves inches per year,” Camp says, “some tens or hundreds of feet.”

It’s ground water that keeps a river flowing during a dry summer.

An aquifer can cover a huge expanse of land, Stuckey said.

“If you look at a map of northwest Ohio, there’s an aquifer that covers basically all of Williams County, the west third of Defiance County, the west fourth of Fulton County,” he said. “They can be rather extensive.”

That doesn’t mean the entire area is suitable for wells. Some portions of the aquifer could be thinner than others, and other factors can play a role.

Preliminary indications point toward a successful drilling operation on Brawley’s land. If that becomes the new source of Fayette’s drinking water, what exactly is the nature of the liquid that will begin pouring from faucets next year?

Could this be ancient water from a glacier that melted 125,000 years ago?

This is the point where Joyce Dunkin says there’s nothing but old water, and George Stuckey agrees.

“All the water we have was here right after the planet was formed,” he said. “It’s just recycled water.”

But this water that’s pumped from 185 feet underground—is it pure glacial melt?

“Generally, the deeper you go, the ‘older’ the water,” says Stuckey, and Dunkin concurs, adding that there are exceptions.

“There is movement from the surface down,” she said. “It’s very slow. It’s like dumping water on beach sand. It disappears and emerges somewhere else.”

Eventually, it’s going to work its way down.

“Ground water is continually reacting with surficial water,” Camp explains. “It’s a mixture of percolating water from precipitation and irrigation, snow melt, organic decomposition, ancient water trapped in bedrock millions or hundreds of millions of years ago.

“Some ground water comes from earlier glacial melt, but this is not the only source.”

The higher land northwest of Fayette in Hillsdale County serves as a major recharge area, joining the general southeastward flow of regional ground water. This is what fills the aquifer below.

A dose of glacier melt, a dollop of rainfall, a measure of Hillsdale County’s finest—all that old water melds together to produce what will likely become Fayette’s new water.

Glacial Geology

Evidence of “Ice Age” glaciers is obvious now, but as the nineteenth century unfolded, few people understood the clues left behind. There was no alternative to Noah’s great flood to explain the land forms of the northern hemisphere.

A European mountaineer was among the first people to suspect glaciation and he explained his ideas to a young Swiss naturalist named Louis Agassiz. Much like everyone else, Agassiz was unbelieving, but not for long. The evidence was too strong.

Wherever Agassiz traveled, he saw traces of the past, such as boulders out of place high in the mountains, scratches etched into bedrock and terminal moraines—the mounds of dirt pushed up by glaciers and left behind after melting.

Visits to Britain, Germany and the United States led him to believe that glaciation occurred on a massive scale. Subsequent studies revealed a picture of the past in which more than a third of the planet was covered by ice. The ice advanced and retreated repeatedly over the course of hundreds of thousands of years.

Agassiz was so enthralled with American geology that he made his home in the United States and became known as one of the foremost educators in the country’s history.

Ice two miles thick remains over Greenland today. Studies of the existing ice packs at both the north and south ends of the globe help scientists gain ideas about the depth of ice in the past.