UPDATE: Low-flying helicopter to complete work Friday or Saturday

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The helicopter to be used for the groundwater study flew all day Thursday and is expected to finish either Friday or Saturday. It will take a year to make a model from the data it collects.

The 750-lb sensor probe towed by a low-flying helicopter will be overhead in Cedar Rapids over the next few days. It's used for a groundwater study in a joint project between the city of Cedar Rapids and the United State Geological Survey. Monday, May 1, 2017 (Dave Franzman/KCRG-TV9)

The helicopter was grounded Tuesday and Wednesday due to wind and other issues.

If anyone sees a low-flying helicopter carrying a torpedo-shaped object near the Cedar River, It’s not an aircraft in trouble.

Rather, what’s you’re seeing over the next few days in Cedar Rapids is all part of a groundwater survey for the city and the United States Geological Survey.

Drinking water in Cedar Rapids is not taken directly from the Cedar River. Instead, the city depends on shallow wells nearby and finding a new location for a well usually meant consulting maps and drilling test holes.

But an electromagnetic sensor slung underneath a helicopter can eliminate some of the guesswork. That’s because it can direct signals through the ground and map what’s below to a depth of 150 feet.

Greg Delzer, a hydrologist with the USGS, said the kind of survey the city and federal agency are cooperating on is a vast improvement over older methods.

“We’ve been doing groundwater models for years. This is kind of the wave of the future,” Delzer said.

For the city, mapping the aquifer system underground is critical in preparing for future droughts.

Four years ago, the city worried about shallow wells drying up and producing less water for the treatment plants after a dry summer in 2012. The utilities department even dug a 600-foot-long trench to the Cedar River to draw in river water to recharge the well fields.

Knowing water capacity underground and where new wells should go for future expansion is critical for growth in Cedar Rapids.

Bruce Jacobs, the engineering manager at Cedar Rapids Utilities, said “the water system in Cedar Rapids is an important part of the economy. We have several grain processing industries that utilize water in significant amounts.”

The helicopter towing the sensor can cover a lot of ground. It will pass about 100 feet overhead at a speed of 70 miles per hour.

The subsurface aquifer information produced by the sensor will be compiled into a report by the USGS and released in about a year. It will be available to the public.