Table 2-8. Maximum Seasonal Depth of Frost for an Air-freezing Index 

 of 850 degree-days °F 



Soil type 



Frost penetration ( j n . ") 



Bare ground Turf Turf + 12 in. 



Clay and damp top soil 



Silt and sandy silt 



Silty sand 



Sand and silty sandy gravel 



Gravel and sand 



Glacial till 



Well-drained, sandy gravel 



21 

 30 

 36 

 40 

 46 

 50 

 56 



13 



20 

 24 

 26 

 29 

 33 

 37 



9 



14 

 16 

 18 

 21 

 24 

 26 



Table 2-9. Maximum Seasonal Depth of Frost for an Air-freezing 

 Index of 1300 degree-days°F 



Soil type 



Frost penetration ( in . ) 



Bare ground 



Clay and damp top soil 



Silt and sandy silt 



Silty sand 



Sand and silty sandy gravel 



Gravel and sand 



Glacial till 



Well-drained, sandy gravel 



30 



41 

 48 

 52 

 59 

 64 

 78 



Turf 



20 

 29 

 35 

 38 

 44 

 48 

 54 



Turf + 12 in. 



14 

 22 

 26 

 28 

 32 

 36 

 39 



2-32 



