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EM 1110-2-1913 31 Mar 78 .: alignment is always an excellent means of obtaining useful information. Physical features to be observed are listed in table 2-2, These items and any others of significance should be documented by detailed notes, supplemented by photographs. Local people or organizations having knowledge of foundation conditions in the area should be interviewed, 2-5, Report, When all available information has been gathered and assimilated, a report should be written that in essence constitutes a geological, foundation, and materials evaluation report for the proposed levee. All significant factors that might affect the alignment and/or design should be clearly pointed out and any desirable changes in align- ment suggested, Section II. Subsurface Exploration 2-6, General, a, Because preliminary field investigations usually involve only limited subsurface exploration, only portions of the following discus- sion may be applicable to the preliminary stage, depending on the nature of the project, b. The subsurface exploration for the design stage generally is accomplished in two phases, which may be separate, in sequence, or con- current: (1) Phape 1, the main purpose of which is to better define the soil types present and to develop general ideas of soil strengths and permeabilities; (2) Phase 2, provides additional information on soil types present and usually includes the taking of undisturbed samples for testing purposes, . 2-7, Phase 1 Exploration, Phase 1 exploration consists ~ost entirely of disturbed sample borings and perhaps test pits excava~ed with back- hoes, dozers, farm tractors, etc., as summarized in table 2-3, but may also include geophysical surveys which are discussed later. 2-8. Phase 2 Exnloration, Phase 2 subsurface exploration consists of both disturbed end undisturbed sample borings and also may incluce geophysical methods. Undisturbed samples for testing purposes are some- times obtained by handcarving block samples from test pits but more usually by rotary and push-type drilling methods (using samplers such as the Denison sampler in extremely hard soils or the thin-walled Shelby tube fixed piston sampler in most soils), Samples for determining con- solidation anC sllear strength characteristics and values of density and permeability should be obtained using undisturbed borings in which 5-in,-diameter samples are'taken in cohesive materials and 2-4 .