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EM 1110-2-1913 31 .Mar 78 e 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 kno\rledgeof 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) Ph~e 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 almost entirely of disturbed sample borings and perhaps test pits excavated 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 Exploration. Phase 2 subsurface exploration consists of both disturbed and undisturbed sample borings and also may include 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 and suear 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 e "