The Weather Service this winter has recorded frost depths of 49 inches in the Bismarck area and more than 53 inches in the Williston, N.D. area. Such measurements are relatively new, but Schlag estimates that a normal depth in inches for Bismarck would be in the high 20s to low 30s.Click to see full answer. In respect to this, how deep is the frost line in my area?Whereas the average depth of frost for our region is between 15 and 20 inches, the established depth frost line varies from 36 to 48 inches. So, the frost line is a “safe” distance beneath the surface of the ground where soil and anything layed within it will not be affected by freezing temperatures.Likewise, how deep is the frost line in Northern Virginia? As for the depth, you need to dig down to the locally accepted frost depth. In most of Northern Virginia, that is 24″ down. If you live farther north, you may be digging down three or four feet. Also to know is, how deep is the frost line in Iowa? DES MOINES, Iowa — The National Weather Service reported Thursday that the frost depth is now more than 25 inches deep.How deep are water lines buried in North Dakota?“Most water line projects call for water lines to be 8 feet deep.” Geneva Kaiser, manager of Stutsman Rural Water District, said the district hadn’t received reports of any frozen water lines, although rural water districts in northern North Dakota had.