The Ice Cometh: How much weight can it hold?

When I was a kid, I went with a brother and a couple of friends down to our local river on a cold December Sunday morning. We found the river (actually at that place an estuary, its water level determined by Lake Michigan) frozen clear as glass.

We first thought of skating – but was the ice thick enough? We dropped a couple softball-sized stones from the bridge and, instead of breaking through, each landed with a solid thock! That sent us scrambling down the embankment to the water. One by one, we inched out from shore, the water under the ice less than a foot deep. We kept inching farther, staying well apart, still over shallow water. A few stress cracks showed the ice to be about two inches thick. Mustering our courage, we each tried jumping and landing hard. The ice held firm. Then we moved together into a circle and jumped in unison. Still no sign of weakness.

We ended up skating (with parents’ permission) for hours that day, on ice so clear we could see every detail on the bottom, two to four feet down. But were we really safe? Just how strong is ice? How thick does it have to be to walk on, skate on, drive a car on? I grew up with an old saying, allegedly from someone’s grandfather, that “Two inches of ice will hold a team of horses.” Every authoritative source I’ve read lately contradicts that.

Any discussion of when ice is “safe” must account for the possibility of springs, flowing water underneath (as on a river), snow on top, objects like logs or rocks protruding, recent temperature changes (have there been any freezing/thawing cycles?) and the condition of the ice itself (late-winter ice that is honeycombed is notoriously hazardous). Most experts will tell you there is no such thing as “safe” ice – venturing out is always at your own risk.

Even when we’re talking about clear blue ice – the kind formed from calm, very cold nights – authorities disagree on how much ice is acceptable. Some say to stay off ice three inches or less in thickness. Others say less than two inches will do in some circumstances. I have skated on river ice barely two inches thick. It was creaky, but I didn’t worry too much because I stayed near the bank, over water no more than a foot or two deep. If the ice broke I would at worst end up with cold and very wet feet and lower legs, and the river was right behind my house, so a warming place was nearby.

I won’t be so casual venturing out onto Birch Lake, where the depth just a few dozen yards from our shore drops to eight feet and more. If you’re looking for a little guidance on ice safety, here are a couple of perspectives from knowledgeable sources. The Lincoln (Neb.) Fire and Rescue dive and water rescue team gives this advice:

·        Less than 3 inches: Keep off

·        4-5 inches: Ice fishing and skating (person up to 250 pounds)

·        6-7 inches: Snowmobile or ATV (1,100 pounds)

·        8-11 inches: Light car or truck (3,500 pounds)

·        12-14 inches: Medium truck (8,000 pounds)

The U.S. Army Corps of Engineers breaks it down this way:

·        Less than 1.75 inches: Keep off

·        1.75 inches: One person on skis

·        2 inches: One person on foot or skates

·        3 inches: One snowmobile or a group of people walking single file

·        7 inches: Automobile

·        8 inches: 2.5-ton truck

·        9 inches: 3.5-ton truck

·        10 inches: 7- to 8-ton truck

This guidance applies to clear, blue, sound ice. So the old folk wisdom about the team of horses is not to be trusted. Here is an old saying you can live by:

Thick and blue, tried and true.

Thin and crispy, way too risky.

When in doubt, don't go out.