Priorities and Levels of Severity

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The City's response is based on the amount of snow that accumulates on the road. The first priority for City plows are the primary routes which are the major arterial streets such as Colorado Boulevard, Washington, 104th, 120th, 136th. Next to be plowed are the secondary routes which include local collector streets, school zones, and fire station zones. The last to be plowed are the residential streets. Residential streets are only plowed after major snowstorms such as the blizzard of December 2006.

Levels of Severity

There are three levels of response to snow emergencies, depending on the severity of the storm...

Class I � An event that results in less than four inches of snow accumulating on the road surface, lasts less than 12 hours, and can be handled by City personnel.
Class II � A storm that lasts for more than 12 hours; snow accumulations of between 4 and 8 inches and may require some contractor assistance in addition to City staff.
Class III � Snow accumulates on road surfaces to depths greater than nine inches, lasts for more than 24 hours and requires contractor assistance and City crews to plow at least one lane in all 262 miles of City streets.

During a Storm

In a Class I or Class II storm, City crews will plow only selected streets identified as Primary and Secondary routes. Primary routes are arterial streets and Secondary routes include local collector streets, school zones, and fire station zones. Primary and Secondary routes make up 217 miles of Thornton's street system. In a Class I storm, Primary routes are treated within three hours of the snow beginning to accumulate on roadways. Secondary routes will be cleared of snow and ice after the primary routes are completed.

During Class II and Class III storms, snowfall may be so heavy that only Primary routes can be maintained in a passable condition until the storm abates. When Primary routes are clear, then Secondary and Residential routes are plowed. Residential streets are only plowed during Class III storms.