Routine sampling of water important for well owners

CHAMPAIGN, Ill. — Private well owners are responsible for the safety of their water.

“Well construction and drillers are regulated, but after that it is up to the owner of the well to take care of it,” said Steve Wilson, groundwater hydrologist at the Illinois State Water Survey, a division of the Prairie Research Institute at the University of Illinois.

“The water can be colorless, odorless, have no taste and it can still have contaminants,” said Wilson during a Groundwater and Well Construction 101 webinar. “One example is arsenic so the only way to know if it is there is by sampling.”

Wilson advises well owners to sample their water.

“You should sample your well annually for coliform and nitrate and every three to five years for metals,” he said.

Permeability indicates how fast water can move.

“Water moves based on pressure and it wants to stay level,” Wilson said. “It takes pressure differences between the well and aquifer to cause water to flow into a well.”

As the grains get smaller, the water flow is reduced.

“Clay grains are so small that water can hardly get through it,” Wilson said. “But in gravel, water can move up to 3,000 feet per day.”

Groundwater is always in movement because of pressure differences.

“In Illinois, we get about 38 inches of rainfall per year,” Wilson said. “Our sand and gravel aquifers along streams can get from 10 to 12 inches of recharge whereas a buried aquifer may get a quarter inch of recharge per year.”

Several different types of wells exist including dug or bored.

“A lot of older wells are dug or bored and they are usually large diameter wells,” Wilson said.

A drilled or driven well has a well screen.

“The screen is sized depending on the gravel in the formation, so the screen is sized to keep the sand out and let the water in,” Wilson said. “Every well is different, but a 200-foot well might have a screen at the last 5 to 10 feet and then there is solid pipe above it.”

A bedrock well is drilled into bedrock and the water comes from the fissures in the rock.

“Most of these wells only have casing 10 to 20 feet into the bedrock and below that the bedrock acts as the casing,” Wilson said.

The well log provides lots of information and it can be obtained from a county health department or the Illinois State Water Survey.

“Logs have been required since 1968 and we get copies from all the counties,” Wilson said. “We have about 450,000 well logs and we estimate there are about 800,000 wells in use.”

The log includes information such as how deep the well is, if it has a screen and where the pump is set.

“Those are things you need to understand because knowing where your water is coming from is half the battle of understanding what might be occurring,” Wilson said.

“If you drill a well, make sure you get a complete well log copy from the driller,” he said. “If the driller won’t give you the log, contact me and I’ll get the state involved to make sure you get your well log because there is no reason for them not to give it to you.”

Wilson highlighted a couple of important issues with wells including old wells that don’t meet current construction codes.

“Construction codes change, but all wells are grandfathered in so we see many hand dug wells that aren’t safe,” he said.

Another issue is lack of well owner knowledge.

“So many people don’t understand what it means to take care of a well,” Wilson said. “Those are folks that should not be well owners.”

Abandoned wells are a big concern.

“In Illinois we probably have 450,000 abandoned wells that no one knows where they are or maybe the landowner knows,” Wilson said.

“People or livestock can fall in these wells and die,” he said. “And tractors can get damaged by these abandoned wells that aren’t properly filled in and sealed.”

For more information about the Illinois State Water Survey, go to www.isws.illinois.edu.