Ice Diving a Reservoir in February

By Ray Whitfield, ADCI-certified commercial dive supervisor. Reviewed by Amanda McCallister, editor.

Potable Water Tank Inspection & Cleaning | Wastewater & Sewer Diving February 11th, 2017. Rampart Reservoir, elevation 8,600 feet. The ice read fourteen inches with a tape and a spud bar, but ice lies. It had that honeycomb look near the shore, and the wind was doing that thing where it sounds like a far-off train. The client's engineer kept saying 'she'll hold,' meaning the ice, meaning his schedule. He was probably right. We cut a triangle hole anyway—three feet on a side, not big enough to lose a truck in but plenty big for a diver. I've been diving icy inland water for twenty-eight years. I'm ADCI-certified, and I've cut a hundred holes in frozen reservoirs, rivers, and settling ponds. February is the month when the work gets weird—when you're cranking through ice while wearing gloves that feel like oven mitts, and then you drop into water that's calm and black and four degrees above freezing. It's not the cold that gets you, most times. It's the dark.

Cutting the Hole

We use a chainsaw on a pole, a twelve-foot bar, and a steel hand auger for the corners. You cut a triangle because a triangle won't rotate under the ice and trap you like a lid on a jar. That's a real thing. A circle is a trap. You mark the ice with a GPS and a rope from shore, because in a whiteout the hole disappears. You also set a spud bar through the ice next to the hole and tie it off—if the hole shifts or closes, you've got a solid reference. You test the ice with a spud bar every ten feet as you walk out. Thick ice doesn't always mean good ice. If it's white and layered, it might be rotten. Clear blue ice is what you want.

Going Down

Everything goes on twice. You struggle into a dry suit with latex seals and a long underwear layer. You use a full-face mask with a heated lens or a standard mask with an ice-resistant regulator. Two regulators, actually. Redundant air. You tape a dive computer to your forearm under the suit, so it reads the water temp and depth. You don't want the console freezing and pretending you're at 90 feet when you're at 12. The tether—a three-quarter-inch nylon line—gets clipped to your harness with a locking carabiner. The tender holds the other end. You agree on signals before you go: two pulls for 'give me slack,' three for 'take up,' four for 'I need to talk.' Then you sit on the edge of the triangle and slide in. The water takes your breath away for a second, even through the suit. It's not pain. It's surprise.

Under the Ice

Underneath, the reservoir is a cathedral. The ice overhead glows blue-white, and the light dims fast the deeper you get. Visibility on a good day is fifteen feet—dust and silt the rest. You move slow, one hand on the tether, one hand on the bottom or the wall. The cold seeps in through the seals no matter what. You don't feel it much because you're working. The trick is to keep moving. You check the intake screens, the valve gates, the structure. You carry a small underwater light, but you don't need it near the hole—that's your beacon. The temperature reads 0.5°C on my wrist. It doesn't drop below zero because it's still water. You don't think about that. You think about the tether.

The Tender's Job

The tender is the most important person on the ice. They keep the line slack from tangling, they feel your movements, they watch the clock. We run a second diver dressed and ready on the surface. If I need help, I do two hard pulls, and the standby diver is in the hole in under a minute. That's the rule. Not forty seconds. Under a minute. The tender also talks to me through the comms line if we have it, but on a lot of jobs it's just rope signals. I've done it both ways. Rope signals are honest. There's no static. It's just you and the line and the person pulling on it. When I come back up, the first thing I see is the triangular patch of sky. The wind hits my face. The tender's gloves are frozen to the line. That's the moment I know I'm back.

Why February

You might ask why do we do this in the dead of winter. Because the work is scheduled. In a reservoir, the water level drops in the winter drawdown, and certain structures—intake gates, stop logs, trash racks—are only accessible when the water's low. The ice is just the price you pay for that access. Also, in some places, the water is clearer in winter. Plankton dies back; visibility sometimes doubles. February is the sweet spot for many high-altitude reservoirs—cold enough for solid ice, but not so cold that your suit freezes into a board. You learn to pick your days. You watch the forecast. You listen to the ice when you drive the snowmobile out. It pops and groans like a house settling. That's normal. If it starts ringing, you stop.

Frequently Asked Questions

Isn't it dangerous to dive under ice? It is, if you skip the rules. The danger isn't hypothermia or getting lost—it's mechanical failure and human error. That's why we use redundant air, a tether, a standby diver, and a proven hole shape. The cold makes everything stiff, so you train for the fail modes. What happens if you get tangled or the tether breaks? We've all had near misses. If the tether breaks, you're supposed to go to the surface immediately—that's where the air is. You can also carry a spare independent inflatable marker that floats a line to the surface. But the best answer is prevention: the tender keeps tension, and you never go further than the line allows. How long can you stay under? On a typical inspection, maybe thirty to forty-five minutes. The limiting factor isn't air—it's cold. Your hands and feet get stupid, and cognitive function drops. When that starts, you end the dive. You never push it.