In the early days of Fairbanks, before the hazard of permafrost was fully understood, subsurface explorations were not common and as a result many buildings were unwarily constructed on non-thaw stable permafrost. In some cases, it didn't take very long for the presence of permafrost to be discovered. In some cases, builders actually had full knowledge of permafrost but overestimated the ability of buried insulation to prevent thaw (many came from the oil producing states of the Lower 48). The resulting distress varied and evidence of this can be seen all around the Golden Heart Interior. Some more infamous buildings can be seen on Army Road and Madcap Lane off of Farmers Loop Road, not far from UAF. Some of the distressed buildings in this area serve as temporary housing for UAF students and others. While these structures can be found in various stages of distress, they continue to safely shelter the inhabitants and serve as rentals. However, some distressed buildings eventually became uninhabitable and some were ultimately demolished.
With the passage of time, experience and knowledge of the hazards associated with permafrost grew and eventually site exploration became more commonplace. Accordingly, problems were reduced, and a knowledge-base was developed. Fast foward to the present and areas that were generally permafrost-free were identified and these have since been developed. Continued development has depleted the available permafrost-free land and this has forced many builders, in search of good ground (in areas close to Fairbanks), toward the boundaries between "good ground" and those containing pervasive frozen ground. These in-between areas can be especially hazardous. A small deposit of ice rich permafrost (or seasonal frost) under one corner of a proposed building footprint is not easy to find without drilling a lot of boreholes. But a small deposit of frozen ground can be more than enough to cause considerable damage to a structure, and great financial distress to its owner.
Historically, in the areas identified as generally "safe" (which had been explored and where permafrost was seldom encountered), one or two boreholes (test pits generally cannot explore the depths required and they disturb large areas of ground) for a modest building was the accepted standard for many years. But as the "good ground" was developed and development continued toward questionable areas, a increasing number of distressed foundations made it clear that the areas bounding permafrost areas (and generally mapped as "permafrost free") might contain mostly non-frozen ground but could still conceal localized pockets of frozen material that were themselves large enough to seriously damage a building, resulting in costly repairs that often amounted to a sizeable portion of the market value of the structure, especially residential structures.
Limiting exploration to one or two building corners meant the other areas were left to chance and in some areas, the likelihood of changing conditions from borehole to borehole was great and this fact prompted engineers (such as the author) to suggest additional exploration.
Today, a subsurface investigation can consist of any number of soil borings, depending on the size of the building and its location. While no practical number of boreholes can rule out all risk, a greater number of boreholes can go a long way towards reducing risk. SYNGEN's strategy towards investigating subsurface conditions in permafrost boundary areas includes the use of thermistor probes for temperature measurements to more thoroughly characterize subsurface conditions across the building footprint, identify hazards, and reduce risk.
