The number, thickness, and depth to top and bottom of soil layers in the
STATSGO data varies widely from one soil component to another, even
within the same map unit.  This makes it difficult to use the STATSGO
data in models, especially if they require rasterized (gridded) data.
To facilitate rasterization of the STATSGO data and physical and
hydraulic properties derived from it, we converted the STATSGO layers to
a set of 11 standard layers, as follows:

   Layer        Thickness       Depth to Top    Depth to Bottom
        
     1         5 cm (2 in)        0 cm (0 in)     5 cm (2 in)
     2         5 cm (2 in)        5 cm (2 in)    10 cm (4 in)
     3        10 cm (4 in)       10 cm (4 in)    20 cm (8 in)
     4        10 cm (4 in)       20 cm (8 in)    30 cm (12 in)
     5        10 cm (4 in)       30 cm (12 in)   40 cm (16 in)
     6        20 cm (8 in)       40 cm (16 in)   60 cm (24 in)
     7        20 cm (8 in)       60 cm (24 in)   80 cm (31 in)
     8        20 cm (8 in)       80 cm (31 in)  100 cm (39 in)
     9        50 cm (20 in)     100 cm (39 in)  150 cm (59 in)
    10        50 cm (20 in)     150 cm (59 in)  200 cm (79 in)
    11        50 cm (20 in)     200 cm (79 in)  250 cm (98 in)