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Western Dam Engineering Technical Note 3 identified. The investigation plan might also include phone numbers to communicate events, written procedures to help promptly deal with unusual conditions or damage, and guidelines for the work associated with the drilling and sampling. Typical Sampling Methods Appropriate sampling methods vary based on the target strata being investigated. This is a general summary of typical methods for obtaining samples to characterize embankment dam materials. Refer to the referenced ASTM standard for detailed information on each sampling type and method. Photo 1.Example Samplers (Photo Courtesy of CME) Split spoon sampling using Standard Penetration Test procedures (SPT) (ASTM D1586): A split spoon sample is a driven-sample generally obtained using the SPT method. This provides both an in situ test of the relative consistency (density/stiffness) of the material and obtains a disturbed sample. Split spoon samples can be performed in most soil types and weak rock, but are not appropriate for strong rock. If the material is non- cohesive (sandy), then various catchers may be used at the sampler tip to help retain the sample; however, these may affect SPT results is low strength material. The resulting sample is appropriate for index testing (gradation, plasticity, moisture content, etc.). Samples should be removed from the sampler and placed in sealed plastic baggies to retain moisture. (Laboratory testing of samples will be discussed in a subsequent issue.) Thick-walled split tube sampling (i.e., modified California sampler, ASTM D3550): is a driven-sampling method using a ring-lined barrel that provides a slightly less disturbed sample of soils and weak rock, but is not appropriate for strong rock. This sampling method is also often used following SPT procedures. It is preferred over the split spoon when a less disturbed sample is desired and the material has sufficient cohesion to be retained in the sampler. The ring sample should be carefully sealed with wax or taped plastic caps. The ring samples can best be used for index property characterization (gradation, plasticity, moisture content, etc.). Use caution performing tests on these samples, when they are intended to represent in-place properties such as density and strength, as some disturbance of the soil likely occurred. Thin-walled sampling (i.e., Shelby tube, ASTM D1587): Shelby tube sampling is a push-sample method that provides a relatively undisturbed sample of fine-grained, cohesive material. It may be difficult for sampling non- cohesive or granular material such as sands or gravels, as they are difficult to retain in the tube, although special procedures have been developed for thin walled sampling of sands using fixed piston samples, which provide for development of vacuum in the soil pores during sample extraction. Tube sampling of sands requires great skill and care and special precautions must be taken to limit disturbance of these samples during transportation. Quality Shelby tube samples are appropriate for testing index properties as well as in- place characteristics such as density, consolidation, and strength properties, as this method generally results in the least disturbance of soil sampling when performed properly. Samples should be retained within the tube to allow the laboratory to carefully extrude the sample. Sample disturbance and change in sample condition is likely if the sample is extruded in the field. The tube should be carefully sealed with wax or o-ring packers. Care should be taken to avoid sample disturbance during transportation to the laboratory, especially for soft soil samples. Core sample: A “core” sample refers to a relatively continuous sample recovery of the drilled material. Core samples are obtained through the drilling process itself. Sample cores can be relatively undisturbed or disturbed based on the drilling method used. Core samples can be obtained using diamond coring, sonic drilling, and even auger drilling when a plastic-lined auger string is utilized. Undisturbed core samples are appropriate for testing index properties as well as in-place properties such as Split Spoon Shelby Tubes California Tube Sampler