Snow Trigger Depth
What is Snow Trigger Depth?
Snow trigger depth is the measured amount of snow or ice that must build up on a site before a snow contract sends a crew out, such as a 2 inch trigger. It is not the accumulation threshold, the most snow the site is allowed to hold, and it is not the total accumulation a per-inch rate is billed on. Zero tolerance is not a depth at all: the Snow and Ice Management Association calls it a general term for low tolerance that does not, on its own, set a level of service.
The trigger and the accumulation answer different questions, and a contract that blurs them gets argued about in February. The trigger decides whether a crew goes out: SIMA’s standard glossary defines trigger depth as “the agreed upon measurable amount of accumulated snow or ice wherein snow and ice management services will be dispatched.” The accumulation decides what the visit is worth when price moves with depth: SIMA’s per-event fee is typically bounded by “amount of accumulation (range of inches/centimeters)”. A storm that crosses a 2 inch trigger and ends at 6 inches is one storm event, however many pushes it takes, and a per-inch contract bills the 6. The snow removal pricing calculator prices that split with a per-inch tier schedule above your trigger depth.
SIMA’s accumulation threshold, “the agreed-upon maximum amount of snow or ice accumulation acceptable”, is a third number, and the glossary warns it is “Not to be confused with Trigger Depth”: one is a promise about the site, the other a start signal.
A contract states the trigger as a number and a unit (inches in the US; the Canadian snow contract template writes it in centimeters), where it is measured, which services it starts, and the completion time that goes with it. SIMA sets no depth, so the number is whatever both parties sign; the snow removal contract template puts it beside the response window.
Zero tolerance is what clients ask for and contracts cannot price as written. SIMA calls it “a general term used to describe a low tolerance for snow and ice accumulation levels” and says “the descriptor alone does not designate a Level of Service”. Write the accumulation threshold and completion time instead. Which billing structure carries that risk is covered in structuring 2026-27 snow contracts.