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EM 1110";'"2-1913 31 Mar 78 alignment is always an excellent means of obtaining usefu Physical features to be observed are listed in table 2-2. and any others of significance should be documented by de supplemented by photographs. Local people or organizatio knowledge of foundation conditions in the area should be 2-5. Report. When all available information has been ga assimilated, a report should be written that in essence c geological, foundation, and materials evaluation report f levee. All significant factors that might affect the ali design should be clearly pointed out and any desirable ch ment suggested. Section II. Subsurface Exploration 2-6. General. a. Because preliminary field investigations usually limited subsurface exploration, only portions of the foll sion may be applicable to the preliminary stage, dependin of the proj ect. b. The subsurface exploration for the design stage accomplished in two phases, which may be separate, in seg current: (1) Phape 1, the main purpose of which is to be soil types present and to develop general ideas of soil s permeabilities; (2) Phase 2, provides additional informat types present and usually includes the taking ofundistur testing purposes. . information. These items ailed notes, shaving nterviewed. ~- hered and nstitutes a r the proposed nment and/or nges in align- '" involve only wing discus- on the nature enerally is ence, or con- ter define the rengths and on on soil ed samples for . 2-7. Phase 1 Exploration. Phase 1 exploration consists lmost entirely of disturbed sample borings and perhaps test pits excavat d with back- hoes, dozers, farm tractors, etc., as summarized in table 2-3, but may also include geophysical surveys which are discussed late . 2-8. Phase 2 Exploration. Phase 2 subsurface exploratio consists of both disturbed and undisturbed sample borings and also ma include geophysical methods. Undisturbed samples for testing pur oses are some- times obtained by handcarving block samples from test pit but more usually by rotary and push-type drilling methods (using s plers such as the Denison sampler in extremely hard soils or the thin-w lled Shelby tube fixed piston sampler in most soils). Samples for de ermining con- solidation and shear strength characteristics and values f density and permeability should be obtained using undisturbed bor'ngs in which 5-in.-diameter samples are" taken in cohesive materi Is and 2-4 "" .