WATERVILLE — April is a busy month for Michael Gagnon. As a mechanic in Winslow, he sees a huge uptick in business. It’s all thanks to potholes.

When groundwater seeps underneath Maine pavement, it’s likely to freeze. When this happens, the ice expands, and the pavement follows suit, bending and cracking in the process. Come March and April, melting ice leaves gaps under the surface of the road, and when cars drive over those gaps, potholes form.

When potholes fill with water and freeze again, they only get bigger. With wet winters and plenty of false starts to spring, central Maine becomes prime territory for potholes.

At North Pond Road Mechanics, Gagnon spends his spring fixing suspension damage to cars caused by potholes. This can mean replacing shocks, struts and broken springs or even more severe damage. In the last few weeks, Gagnon has delt with broken exhaust and tailpipes two or three times a week.

“(Pothole damage) is showing its ugly head,” he said.

These kinds of repairs can range from about $200 to $1,500, and no make or model of car is safe.

For the city, potholes make April a tough time of year. Waterville’s Department of Public Works has two crews with three workers each dedicated to filling potholes. At the moment, those crews are going out four to five days a week for seven- to eight-hour days, Matt Skehan, director of Public Works, said. A normal-sized pothole generally takes about 15 to 20 minutes to fill.

But filling potholes is not always the permanent solution people might expect, Skehan said.

In the winter, the asphalt mix available to fill potholes is called cold patch. Cold patch doesn’t bind in the same way hot mixes do, so freeze and thaw events and heavy rains can disrupt the patches. Skehan said cold patch might last for a month or two, but it is not designed to be permanent.

Hot mix asphalt requires warmer temperatures, so hot mix plants generally close for the cold season. Waterville gets its materials from Pike Industries, a materials and construction company in Maine, New Hampshire and Vermont. Pike Industries usually begins making hot patch mix in April, and Skehan said that makes “a world of difference.”

In Waterville, a crew will generally fill a pothole within 24 hours of getting a call, so Skehan encourages residents to call in the potholes they see in the streets to the Department of Public Works.

Gagnon said people should slow down when driving on pothole-filled roads.

“I watch people speed down this road at twice the speed limit. If people just slow down a little bit, they probably have a better chance of not wrecking their car,” Gagnon said. “But I’m not an advocate for that, because it makes my business very, very, very busy.”

Waterville’s Department of Public Works can be reached at 207-680-4749, and Winslow’s can be reached at 207-872-1972.