Detailed Soil Survey of the Mount Revelstoke Summit Area.

The soils are divided as (1) coarse-grained soils, (2)fine-grained soils, and (3) highly organic soils . The coarsegrainedsoils contain 50 percent or less material smaller thanthe No . 200 sieve, and fine-grained soils contain more than 50percent material smaller than the No . 200 sieve . Highly organicsoils can generally be identified visually .The coarse-grained soils are subdivided into gravels (G)and sands (S) .The gravels have the greater percentage of thecoarse fraction (that portion retained on the No .200 sieve) retainedon the No .4 sieve, and the sands have the greater portion passingthe No . 4 sieve . The four secondary divisions of each group - GW,GP, GM, and GC (gravel) ; SW, SP, SM, and SC (sand) - depend on theamound and type of fines and the shape of the grain-size distributioncurve .Fine-grained soils are subdivided into silts (M)and clays(C), depending on their liquid limit and plasticity index . Siltsare those fine-grained soils with a liquid limit and plasticityindex that plot below the "A" line in the diagram in Table 13, andclays are those that plot above the "A" line .The foregoingdefinition is not valid for organic clays since their liquid limitand plasticity index plot below the "A" line .The silt and claygroups have secondary divisions based on whether the soils have arelatively low (L) or high (H) liquid limit .The highly organic soils, usually very compressible andwith undesirable construction characteristics, are classified intoone group designated by the symbol "Pt ."