Frost boils are created when frost in the roadway sub-base melts in the spring but can’t drain away due to the frozen ground below it. The soggy roadbed eventually heaves, softens and fails, causing the pavement above the sub-base to fail. The crews are removing all the bad section of paving and sub-base material deep enough to get back to a solid road base. After all the saturated soil is removed they will fill the excavation with compacted aggregate and compact it back in place. The pavement will be replaced soon after.