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<br />i;;,'l!ts; <br />~~??~ <br /> <br /> <br /> <br />~if~~~t/ <br />~<;?::~':~- <br />~",-.. "'"--'., <br />"''-'"...-. <br /> <br />~;l~~~~~~~~:;r~~~~i"d <br /> <br />00.,,,:, ',P-/"j <br />UKl..: - <br /> <br />cmmINED STATUS REPORT <br />Periods #6, 7, 8 & 9 !~ <br /> <br />{11 <br /> <br />This status report on the monitoring program of Rainbow Bridge National 110nument <br />covers the period from October 1975 through September 1977. The period numbered <br />6, 7, 8 and 9 denote semi-annual timing of visits for making surveys when the <br />cumulative effects of the higher summer and lower wint,er temperatures have max- <br />imized. <br /> <br />GE:>lERAL <br /> <br />Scheduled surveys were made during the semi-annual visits on established quad- <br />rilaterals at Rainbow Bridge and along Bridge Creek Canyon, the Whittemore Strain <br />-Gage Stations were read and photogeology series photographs were taken at all <br />photopoints. During October 1976, all triangulation and elevation data to date <br />were recomputed by computer because the older hand method was proving burdensome, <br />and some minor cumulative and ~um&n errors were appearing as a result of inde- <br />pendent calculations. Comparison of the computerized data from one period to the <br />next has proven the accuracy of method. The earlier survey readings indicated <br />some very small differences were occurring in the Bridge but these were noted to <br />be the same pattern from year to year and when compared to the pattern of <br />Whittemore Strain Gage readings, it was found that all readings varied directly <br />with air temperature and exposure time to the sun. Later survey and strain gage <br />readings have followed a very predictable pattern contemporaneous with daily and <br />annual air temperature variations. Therefore, the field visits are scheduled <br />during late winter and late summer to take advantage of the more meaningful <br />'temperature extremes as well as the earlier program of pre-spring runoff res- <br />ervoir minimum-summer maximum levels as proposed in Status Report #5. Thus far, <br />surveys and photographic series have shm-m that reservoir action has had no <br />adverse effect on the structural integrity of Rainbow Bridge or Bridge Creek <br />Canyon. <br /> <br />Specific Comments <br /> <br />,The following comments and data relate to subject matter monitored during t~is <br />period: <br /> <br />1. Bridge Creek Canvon Quadrilateral Surveys <br /> <br />Triangulation measurements shm, minute variations of a cyclic nature <br />on an annual basis as expected. Quadrilateral "D" which -.-"(o1as purposely <br />located away from reservoir influence has the same general pattern of <br />annual variation as. Quadrilaterals "A", ":a" and "e" at the Bridge, and <br />in all, the rock has returned to its same positions each session. <br /> <br />2. <br /> <br />Rainbow Bridge Elevation Surveys <br /> <br />These show the same predictable variations as the quadrilateral surveys <br />discussed above. <br /> <br />3. <br /> <br />Whittemore Strain Gage Instrumentation <br /> <br />Continued readings of the rock surface and across several selected <br />fractures on the Bridge are shm.ing very close correlations when com- <br />pared with the same previous season. "linute differences between <br />readings for the same season from year to year are directly related <br />to differing air temperature regimes for the parti,cular years. The <br /> <br />~o/i: <br />~"ir.tAA <br /> <br /> <br /> <br /> <br /> <br />~. <br /> <br /> <br />r~ <br />tI.: <br />;;;'1t~ <br />!":''','~"J.i; <br />c;ji~", <br />.fft;,i:1- <br />i:"~"'__,.- <br />15; <br />ifdg,Z':' <br />~-:fv. <br />f.,!\W' <br />'*.j."-::~ <br /> <br /> <br />