Skip To The Main Content
News & Updates

The fallacy of trigger depths

  • Douglas Freer, CSP
- Posted: June 1, 2014
Included as a part of a service agreement is the scope of work (SOW), which is intended to define the level of service that will be provided. Often, however, the scope is poorly written and may contain contradictory statements. The SOW often outlines how the contractor will perform the work rather than defining the goals, expectations or desired service outcome.

The problem with the standard SOW that defines service as commencing once a specific quantity of snowfall has accumulated (trigger depth) is that it doesn’t take into consideration a number of factors that impact the pavement condition. If the contractor accepts a SOW that limits his response based on that trigger alone, his hands are tied in how service can be completed. The contractor should seek to be held responsible for the service outcome. By clearly explaining what the client should expect, a correctly written SOW will remove the potential for confusion and possible conflict. 

Before agreeing to a SOW, understand your client’s needs by doing a thorough needs analysis. You may not be in a position to change the written scope, but you may be able to include an addendum that clarifies the SOW and the expected outcome based on how it is written and what you are agreeing to do. 

Pin down client’s true expectations
Focus on the service outcome, using trigger depth as a reference point, and ask questions about the client’s expectations regarding accessibility, accumulation and clear pavement during and after a storm event, plus how soon after an event pavement is expected to be in ready condition. I have found many clients can’t provide good answers until we ask scenario-based questions where they can better understand the implications and how we need to respond based on their direction. We attempt to avoid making assumptions and allow clients to make decisions based on the level of service they have chosen. We then write the SOW to reflect the client’s specific needs. 

As you complete your needs analysis and work with the client to clarify the desired response, ask these questions to better identify and understand their expectations. 

Trigger depth 1
Waiting to service until the trigger depth is met can result in compacted snow and crowded lots.

Is the trigger depth a guideline or absolute measurement of when to begin service? 
  • If it’s an absolute, what should be done when there is less accumulation than the stated trigger depth? Who determines the snowfall quantity? Are there exceptions? 
  • If it’s a guideline, under what circumstances should service be performed when snowfall is less than the stated trigger depth?
Should service be performed every time the trigger depth is reached or only after the trigger depth is reached? 
  • The distinction between clearing every time the trigger depth is reached and beginning service once the trigger depth is reached can be confusing. At times clients may write the scope one way but not realize exactly what they are requesting. 
  • The lower the trigger depth the more often service will be performed. If it is to be performed every time the trigger is reached (for example, a 2-in. trigger in an 8-in. storm equals four service visits), proper routing and equipment capacity must be factored to ensure the cycle time for each visit and interval between visits will accommodate the level of service being requested.
  • If service is to begin after the snow accumulation has reached the trigger depth, service will not be performed immediately upon the 2-in. accumulation, resulting in a service delay. How long is an acceptable delay, and how much snow may accumulate (assuming snow continues to fall) before conditions are considered unacceptable? 
  • As an aside, if this is a 24-hour location, are there periods when the level of service may decrease (i.e., snow accumulation may increase above trigger)? 
Does time of day impact the trigger?
Scenario: It’s 6:30 a.m. with 1 inch of snow already on the ground. A store opens at 8 a.m. The contract calls for a 2-in. trigger for service and the forecast calls for continuing snow into mid- to late morning for 2 to 3 inches of total snowfall. Should service be performed prior to opening or wait until there is 2 inches of snow and then service the areas that are accessible? 
  • Waiting until the trigger depth has accumulated will mean that the 2+ inches of snow will have been driven on and compacted prior to service. Not only will this compacted snow have the potential to turn to ice, it now may be more difficult to remove if it has bonded to the pavement. Additionally, waiting to service will mean vehicles in the parking lot reduce accessibility, which may require a return visit after hours to clean up the site.   
  • If service is performed at 6:30 a.m. with a sufficient ice control application, might the remaining snow melt with daytime traffic? How much actual ice will form compared with the first option?  The parking lot will not experience the initial buildup of snow and ice, a complete service will be performed before opening, and likely some nominal return service would be all that is needed during the day to ensure the pavement is relatively clear through late morning hours.
Trigger depth 2
Getting an early jump on an event could result in better service delivery and fewer headaches later.
How does forecast impact the decision if the accumulation is below trigger depth? 
Scenario: An evening event with temperatures in the low 30s with at least 0.75 inch of wet, slushy snow accumulation (below trigger depth), with a forecast of falling temperatures overnight into the mid- to low teens by morning rush hour. Should service be performed with a 2-in. trigger when deicing service is called for only when icy conditions exist? 
  • Letting the slush sit overnight will lead to ice bonding to the pavement, creating an icy condition and one where chemicals are less effective at lower temperatures. While the current conditions do not call for service according to the trigger, pavement conditions will worsen and require service before morning. A 5 a.m. application when the temperature is 15° F and ice has already formed is much less effective in achieving bare pavement by 8 a.m. compared to making an application prior to ice formation. 

Trigger depth 3
Does a 2-in. trigger mean you service after every 2 inches in an extended snowfall or once the storm is done?

How does moisture content of the snow impact the decision to service according to trigger depth?
: A property with a 2-in. trigger and deicing after each plow occurrence receives 1.25 to 1.5 inches of snow that has a high moisture content (less than the typical 10:1 ratio). No additional snow is forecasted for four to five days and temperatures are expected to fluctuate in the low to mid-20s. 
  • According to the SOW, the contractor would withhold service and the property would be covered in ice for at least the upcoming week, increasing the risk of a slip and fall.
  • Deciding to clear the accumulation, despite it being below trigger depth, would provide four or five days of clear and dry pavement.
Is trigger depth for new snowfall only?
  • If there is a half-inch of new snowfall but blowing and drifting creates conditions that result in 0 to 3 inches of snow on-site, should service be performed? If the trigger depth is based on fresh snowfall, then the contractor technically will not be at fault for withholding service unless the SOW defines drifting as a valid service condition. However, most property owners are not going to be pleased with equivalent snowfall in areas of the property that reach the trigger depth. 
  • Are there limits placed on drifting conditions? What if there is no new fresh snowfall but continuing winds create drifting issues requiring service? If the contractor is paid on a per-occurrence agreement, there may not be an issue with providing the additional service. It might be more problematic if limitations are not established under a fixed-fee seasonal agreement. 
How will below-normal temperatures impact your ability to plow according to the trigger depth?
  • When you experience lower temperatures, the use of chemicals is more limited and mechanical removal becomes more of a necessity to remove the precipitation prior to making ice control applications.   
  • Will an absolute trigger depth need to be adhered to when the temperatures are 5° F and clearing is the only effective means to remove the precipitation? 

Trigger depth 4 Trigger depth 5
Ice can form without a snowfall trigger depth ever being met. Extended cold temperatures could further hinder the ability to return the site to ready condition.

Each storm scenario is different, and while the SOW may set the general strategy that you will use to manage the client’s site, the variables at play require a dynamic playbook to manage your clients’ sites. Effectively managing site requirements and client expectations based solely on precipitation measurements is arbitrary and ultimately meaningless. It may be helpful to use snowfall measurements as a benchmark or description, but to base service response on a trigger depth is flawed. You owe it to your clients to be honest about how service should be or will be performed and get their buy in prior to the season. 

Provide meaningful SOW statements that take the interpretation and guesswork out of the language and provide honest descriptions of what your client can expect. Be direct and describe what the site and pavement conditions may be like in certain scenarios. If your client doesn’t like what you describe, then the SOW should change, which will require adjusting equipment, labor and materials along with their budget.  

Doug Freer, CSP, owns Blue Moose Snow Co. in Cleveland.

[Login to add acomment]