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<br />2) General Field Operations <br /> <br />a. Geological Mapping <br /> <br />In specific project areas where more extensive <br />geological mapping is required than is available currently, <br />it is anticipated that the mapping will be accomplished by <br />crews on foot or where possible by remote sensing and aerial <br />photographic methods. In any case, there.will be no dis- <br />turbance of existing vegetation or terrain. Occasional fist <br />sized rock samples will be collected for analysis during the <br />course of the mapping. <br /> <br />b. Geophysical Investigation <br /> <br />The geophysical investigation will consist of seis- <br />mic refraction traverses to determine the depths to various <br />subsurface velocity layers and specifically to the top of the <br />bedrock. The geophysical field crew consists of two or three <br />persons. The equipment consists of electromagnetic geophones <br />spaced at intervals along a geophone cable. This cable is <br />coupled to a recording oscillograph which produces a photo- <br />graphic record of the seismic signals. <br /> <br />As noted below with regard to specific sites, seismic <br />traverses will be concentrated solely along dam axis and canel <br />and spillway routes. Access of the necessary equipment and <br />crew for the conduct of these activities is not expected to <br />require road cuts or construction, involving only use of exist- <br />ing roads or lanes, with some traversing of farm or forest land, <br />and minimal temporary impact impact on such land. <br /> <br />Seismic energy will be'produced by the detonation of <br />small, geletin-based explosive charges. The charges are normally <br />placed at both ends of the traverse. These explosive charges <br />usually consist of 1/2 to 2/3 pounds of 40% geletin buried in <br />shallow, hand dug holes ranging in depth from two to four feet. <br />The explosives are detonated one at a time using electrical <br />blasting caps. Since the charge is very small the danger and <br />noise is minimal, however, care will be taken to be sure the <br />area is clear prior to blasting. As a final precaution, whistle <br />or voice signals are used to alert nearby people of the impend- <br />ing detonation. A two to three diameter hole in the soil is <br />produced which is backfilled with surrounding material. Very <br />minimal, one to two foot diameter local spotbrushing may be <br />required to place some of the geophones along the traverse. <br />However, line-of-site brushing is generally not required along <br />the traverse except as required for survey locations. All <br />equipment, blasting materials, and supplies would be removed <br />from the area upon completion of the surveys. <br /> <br />-4- <br />