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Kennedy/Jenks Consultants • Although not specifically treated in ASTM D2488-06, cobbles range in size from 3 inches to 10 inches and boulders refer to particles with a single dimension greater than 10 inches. They are included here for the purpose of completeness and for their hydrogeologic significance. Note: The ASTM grain size scale differs from the Modified Wentworth Scale used in teaching most geologists. Also, it introduces a distinction between sorting and grading (i.e., well graded equals poorly sorted and poorly graded equals well sorted.) • The modifying symbol W indicates good representation of a range of particle sizes in a soil. • The modifying symbol P indicates that there is a predominant excess or absence of particle sizes. • The symbol W or P is only used when a sample contains less than 15 percent fines. • Modifying symbol M is used if fines have little or no plasticity. • Modifying symbol C is used if fines have low to high plasticity (clayey) The following rules apply for the written description of the soil group name: Types of Soil Rule Sands and gravels (clean) Less than 5 percent fines Sands (or gravels)with fines 5 to 15 percent fines Silty (or clayey) sands or gravels Greater than 15 percent fines • Other descriptive information may include: - Color (e.g., Munsell Soil Color chart, specify edition). Soil color is named and coded using the Munsell Soil Color chart if required for the project. The code should be in parentheses immediately following the written description. Presence of mottling and banding is also recorded. For example, "dk brn (7.5 YR, 3/4)." - Relative Density/Penetration Resistance. For cohesionless materials use very loose, loose, medium, dense, or very dense estimated from drive sample hammer blows or other field tests. Blow counts may be used, if reliable. - Maximum grain size (fine, medium, coarse, as described in AGI data sheets or USCS). Note the largest cross-sectional dimension measured in tenths of an inch for grains larger than sand size. - Composition of grains (mineralogy) - Approximate percentage of gravel, sand, and fines (use a percentage estimation chart as provided in the AGI data sheets) Modifiers Description Trace Less than 5 percent Few 5 to 10 percent Little 15 to 25 percent Some 30 to 45 percent Mostly 50 to 100 percent Monitoring Well Installation Work Plan, B-4 Barrel Ten Quarter Circle Land Company, Escalon, California \\SFO\Groups\I S-GroupW dmi n\Job\03\030118.27_BT QCLC\09-Reports\M W-I nstal I-W Pln\AppendixV:PP_B.doc