SOIL SURVEY

-151 -and path and trails, it is the surface soil texture which is an important consideration. For engineering purposes however, it is the texture of the subsurfac ematerials which is important . The latter is evaluated by the Unified (United State sArmy Corps of Engineers 1957) and AASHO (American Association of State Highwa yOfficials 1961) classifications . Adverse soil textures may sometimes be overcom ewith the addition of topsoil or fill material respectively, but this procedure is costl yand in many cases would be unfeasible .Coarse Fragments .The content of coarse fragments in a soil or on the soil surface will influencethe difficulty of construction of recreational facilities . Coarse fragments on the soi lsurface must be removed when constructing playing fields and will present obstacle sin trails, picnic areas, and campgrounds if they are not removed . Stoniness present ssimilar limitations for most uses and in addition makes excavations more difficult .Slope .Slope is one of the major limitations of many soils in Yoho . Steeply slopin gareas have obvious limitations for such uses as playgrounds or camp areas, especiall ywhere bedrock is close to the surface . Slope increases construction costs and desig nrequirements, and is also one of the major factors influencing erosion hazards .Rockni ess .Rockiness and depth to bedrock are also important soil characteristics fo ralmost all uses . Rock outcrops and shallow depths of soil over bedrock are especiall ylimiting for use as septic tank absorption fields, or as sites for permanent building sand road construction .SOIL LIMITATIONS - AS GOVERNED BY SOIL PROPERTIE SDefinitions of Soil Limitation Classes .Soil Imitation ratings were used to evaluate the soils, and hence the mappin gunits for selected uses . These ratings express relative degrees of hazards, risks o rlimitations for potential uses of natural or essentially undistrubed soils . The long termeffects of the potential uses on the behaviour of the soil are considered in the rating .