California Lacks Safety Standards for Ice Thickness

The U.S. Forest Service, the agency with jurisdiction over Convict Lake, has set no standards for ice thickness, air temperature or other conditions to be met before the public is allowed to venture onto the frozen lake, a spokesman for the Forest Service said Tuesday.

This situation, albeit in a rural area, contrasts with that in many cold-weather cities in the eastern United States and Canada, where standards are set and often rigorously enforced with warning signs, patrols and periodic ice measurements.

In a more rural setting, at Lake Placid, N.Y., officials periodically issue warnings if they feel the ice is unsafe.

Checks with several cities where thousands of people venture onto the ice each winter also showed that in every case surveyed, the thickness of ice required before people were allowed to skate, ice fish, walk or ride on a lake or river was greater than the 2 to 3 inches Mono County sheriffs’ deputies reported at Convict Lake on Monday.

The checks indicated that the further north a city is and the colder its weather in the winter, the more stringent the standards may be.

New York City, for example, requires 5 inches of ice thickness in lakes over 3 feet deep, while Winnipeg requires at least 12 inches thickness of ice, and Edmonton 15 inches. Minneapolis requires 4 1/2 to 5 inches, and restricts the public to only a few areas, which are well patrolled.

All of these cities also have standards for air temperature, and all pay attention to water currents and varying conditions at water inlets as well as placing further restrictions when ice has melted and then refrozen.

At Convict Lake, and apparently elsewhere in California, there are few if any standards.

Fred Richter, Nordic supervisor for the U.S. Forest Service at Mammoth Lakes, said Tuesday that at Convict Lake “there isn’t any standard that I’m aware of. It’s more or less left up to people’s own judgment.”

A spokeswoman at the chief ranger’s office of the National Park Service in Yosemite said that in that park, “we don’t have anything like” the standards in the East and Canada. We leave it to common sense.”

Spokesmen at the state Department of Forestry and Fire Protection and the state Department of Parks and Recreation said those agencies have set no standards.

Officials interviewed in the Eastern and Canadian cities said that establishing safety standards is more than a matter of common sense. There are many intricate factors that have to be carefully studied and calculated, they said.

The National Recreation and Park Assn., in a brochure it has issued on “management aids for natural ice skating surfaces,” cites experiments undertaken by a Rhode Island expert, Arthur Leland. The experiments indicate that ice should be at least 3 3/4 inches thick in snow-cleared, fresh-water lakes before crowds of people should be allowed on it.

If the air temperature is between 30 and 40 degrees, 4 3/4 inches would be required, Leland said, and 12 inches would be required if the temperature was between 40 and 50 degrees.

At Convict Lake, authorities said, the temperature was around the freezing mark at the time of Monday’s accident.

Bryan Thomson, assistant director of citywide park services in New York, said Tuesday that New York generally allows skating when the temperature has consistently been 20 degrees or under and the thickness of clear, dark ice is 5 inches or more for lakes 3 feet deep or more. Even so, city employees measure the ice at least five times a day, and if the temperature rises to 25 degrees, they measure it an additional four times a day, Thomson said.