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• 1.3 MaDD1nQ Methods <br />It was determined that the most rapid, accurate, and economic <br />method to evaluate ground stability would be to make a <br />photogeologic evaluation of the general area through which the <br />alignment was planned. Office work was followed by a field <br />examination, using the photogeology as a basis on which to do <br />additional detailed mapping. An evaluation was made both of color <br />and black-and-white vertical stereoscopic aerial photography <br />provided by PWCC. The color aerial photographs were at the nominal <br />scale of 1"=1000' and were flown on July 1, 1988; the black-and- <br />white photographs were at the nominal scale of 1"=2000' and were <br />flown on May 10, 1990. <br />PWCC furnished base topographic maps for the project at the <br />• scale 1"=400'. An enlargement of the United States Geological <br />Survey Mount Harris orthophoto quadrangle was used as an <br />intermediate plotting medium between the aerial photos and the <br />topographic base. The geologic data annotated on the aerial <br />photographs were plotted to the orthophoto quads and then enlarged <br />in steps to 1"=400'. An aerial photographic map (scale 1"=400') of <br />the entire area also was provided by PWCC and was also used to plot <br />geologic data. The method of data compilation used provided an <br />adequate level of accuracy for the purpose of this investigation. <br />PWCC furnished computer printouts of two topographic maps from <br />which reproducible films were made and on which geologic data were <br />plotted. The following maps accompany this report. <br />a) Exhibit 13-12-1 (Drawing No. 9316-1) <br />• b) Exhibit 13-12-2 (Drawing No. 9316-2) <br />3 <br />