Whether it's during or after snowfalls, or whether the snow has been plowed or not, usually snowfalls affect underground utility surveys in negative ways. If the snowfall is a safety issue and your site is closed due to the snowfall, then we cannot do underground utility surveys. Let's just leave it as that. Otherwise the survey might be able to be conducted, but often the results are less ideal. To decide whether you should go ahead to schedule an underground utility survey when a snowfall is a factor, there are several snow-related issues to be considered. You should consider them along with other factors such as survey purposes, budgets, project time lines, etc.
Spray painting
Spray painting doesn't work well on wet surfaces, whether it's due to rain or snow. The paint will not last long. It can be gone immediately, overnight, after several days or longer, depending on how much water is on the ground surface. If you like the paint to last a long time, you probably want to wait a day or two after the snow is plowed and the ground is relatively dry. However, if it's an area where pin flags can be used such as a lawn area, then it's not a problem.
Visual observations and accesses of ground features related to underground utilities
If the ground is covered with snow, then manholes, valves, utility boxes, pavement patching and other signs indicating underground utilities would be covered. This increases the chance of missing utilities during underground utility surveys since all these ground features could help the surveyor locating their associated utilities. Sometimes just knowing they are there could reduce the chance of missing their associated utilities. Even after snow is plowed, piles of snow in and around a survey area would still affect the survey in a negative way. Snow piles are apparently ground obstacles and the occupied areas could not be surveyed. Even snow piles are outside targeted survey areas, they could still conceal ground features related to utilities which may pass through targeted survey areas. Access to these features or simply knowing their existences sometimes can make a big difference.
Ground penetrating radar (GPR) performance
Snow is usually transparent to GPR, meaning GPR signals can pass through it without losing too much strength. However, it the snowfall is thick, it does affect GPR performances significantly. A ground-coupled antenna is usually used during a GPR survey, meaning it's most effective when the antenna is close to the ground. If the snowfall is thick, the antenna is effectively lifted further away from the ground surface during the survey, causing poorer performances. Below shows an example that an underground pipe is harder to see with the antenna raised higher above the ground.
In conclusion, although a snowfall is not necessarily a prohibitive factor for underground utility surveys, it usually affects them in negative ways -- whether it's during or right after a snowfall, or even after the snow is plowed. Due to technical and operating difficulties related to snowfalls, a survey might need more time to finish (and costs more as a result) and still provide less ideal results. Whenever possible, try to schedule surveys before snowfalls for best survey efficiency and results.
