Lately there have been questions asked by those around Fairbanks about large depressions in the ground. The scale of these circular ‘drops’ in soil are many feet across and from what have been reported (by homeowners) they will be several feet deep so that the lawn hangs like a tarp with a void underneath it (until reaching the descending soil. From a healthy homes view, this could obviously be a safety hazard for any kids or other who are cutting across your yard. But it also may be pointing to potential problems with they home and water supply (or sewer supply).
The main concern I ask about on calls is whether or not the depression is encroaching the foundation. If that happens, it can undermine a cement slab and create voids and cracking. And then radioactive radon gas if present can enter through the void; or if large enough, pests such as insects or rodents may have a new entry into the house. If extreme, it can compromise the load of the structure (especially if it takes place under load bearing walls).
The first question people have though, is what is causing it? It would not be surprising if all of these calls came out of the Gold Stream Valley. There, subsurface permafrost has been fairly active in changing the surface of driveways and yards with large depressions forming in the matter of a summer. But calls of late are from established residences in the city of Fairbanks. If there hasn’t been a history of permafrost nearby (as ice in soils can roam from lot to lot) then there may be a water leak caused by a break in the supply like. Or potentially in the line going to the septic (or sewer when it is city water without a well). The other potential is if there has historically been a large quantity of wood, downed trees, branches, etc….buried that is now decaying and creating a subsurface void. Regardless of the cause, be sure to post the area until you can fill it in and let the water utility (if on city water) so that they can send in detectors for any leaks!