NGA 70 Properties Of Natural Gas And Abnormal Operating Conditions Practice Test

Frost-related exterior loading shows up most clearly as uneven soil settlement and frost heave around the buried pipe. When the ground freezes, moisture in the soil can form ice lenses that expand and push upward, while surrounding soil may settle unevenly as the freeze-thaw cycle continues. This differential movement creates irregular loading on the pipe, often leading to misalignment, bending, or joint stress. That pattern—soil lifting in some spots and sinking in others around the pipe—is the direct physical consequence of frost action on the exterior. The other signs don’t directly reflect frost effects. A consistent soil surface around the pipe suggests stable ground with little differential movement. Uniform gas pressure inside the line pertains to internal conditions, not external loading. Decreased road salt near the burial site isn’t a direct indicator of frost loading on the pipe; it could influence frost depth but doesn’t show the actual exterior loading signature on the pipe.