Work in Tunnels

What is a tunnel?

A tunnel is defined by Minnesota Rules, part 4620.3100 as a below-grade corridor or crawl space that is not used for a human thoroughfare or as an air plenum for any ventilation system.

Are there exceptions for asbestos-related work in a tunnel?

Yes. If your work area meets the definition of a tunnel, then you are exempt from:

• Floor sheeting.
• Wall sheeting.
• Freestanding containments.

However, you are required to make all critical barriers two layers of 6 mil polyethylene sheeting.

All other Minnesota Statutes and Rules apply to the asbestos-related work.

Since I don't have to put a floor in my tunnel containment, should I be concerned about the dirt floor?

Tunnels and crawlspaces are often unfinished spaces with dirt floors. This dirt can be contaminated with asbestos which has fallen off from mechanical systems or from removal of these systems during past renovation work. Asbestos debris can be found both on the surface and also mixed with the soil. This contamination often has to be cleaned up to accommodate future renovation work.

You will need to have soil samples taken by a certified asbestos inspector to determine if there is asbestos contamination present, and the extent of it. Companies that perform asbestos sampling can be found on MDH's Find a Contractor or Consultant web page.

The dirt floor in my tunnel is contaminated. How should this be dealt with?

Once all contaminated objects have been removed from the work area and all visible ACM has been cleaned from the dirt floor, one of the following three options may provide a decontaminated work area for future work. The best option depends on what will work best for your particular situation.

• Encapsulate the dirt floor with a coating that seals in any contamination.
• Enclose the dirt floor with a permanent, impermeable material.
• Remove the surface dirt down to the lowest level of contamination indicated by sampling.

How do I find out more information?

For more information about asbestos, contact the Asbestos Program at MDH through the internet or by telephone at (651) 201-4620.