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MINIMUM REQUIREMENTS FOR NUMBER AND SPACING <br />OF PITS AND BORINGS FOR SAMPLING SOILS AND ROCK <br />Number and spacing of Level 2 sampling pits or borings and Level 3 test borings should conform to the following <br />guidelines. For Level 3, the Geotechnical Engineer will select the locations of borings and the type, frequency, and depth <br />of samples and/or field strength tests. <br />Guidelines for Spacing of Borings <br />Maximum distance between borings, feet <br />Horizontal stratification of soil or rock <br />Project <br />Minimum number of borings <br />Uniform <br />Average <br />Non-uniform <br />Multi -story buildings <br />150 <br />100 <br />50 <br />4 per structure <br />One or two-story buildings <br />200 <br />100 <br />50 <br />3 per 1 structure <br />Land divisions, development site <br />500 <br />200 <br />100 <br />2 per acre <br />4 or less acres <br />Land divisions, development site <br />500 <br />200 <br />100 <br />Minimum 8 per site with 3 <br />4 or more acres <br />per soil unit <br />Bridge piers, abutments, <br />100 <br />100 <br />25 <br />television towers, etc. <br />Roadways, sewers, pipelines <br />1000 <br />500 <br />200-100 <br />Borrow pits <br />500 <br />200 <br />100-50 <br />(for compacted fill) <br />Earth dams, dikes <br />200 <br />100 <br />50 <br />Space preliminary borings 200 to 500 feet apart so that the area between any four <br />New site of wide extent <br />borings includes approximately 10% of the total area. In detailed exploration, add <br />borings to establish geological sections at the most useful orientation. <br />Development of site on soft <br />Space borings 100 to 200 feet at possible building locations. Add intermediate <br />compressible strata <br />borings when building site is determined. <br />Low -load warehouse building or <br />Minimum of 4 borings at comers plus intermediate borings at interior foundations <br />large area <br />sufficient to define subsoil profile. <br />Slope stability, deep cuts, high <br />Provide 3 to 5 borings on line in the critical direction to provide geological section <br />embankments <br />for analysis. Number of geological sections depends on extent of stability <br />problem. For active slide, place at least one boring up slope of slidingarea. <br />Page 1 of 2 <br />