WSP04101

• File Number: 8080
• Description: Section D General Interstate Litigation - Rainbow Bridge Monitoring Program
• State: CO
• Basin: Statewide
• Date: 5/21/1964
• Author: DOI-BOR
• Title: Rainbow Bridge Monitoring Program - Reports 4 through 10
• Water Supply Pro - Doc Type: Report/Study

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Specific Comments
The follovling comments and data relate to specific subject matter
monitored during this period:
1. Bridge Creek Canyon Quadrilateral Surveys
Comparison of differentials in measurements taken 7/12/74 and those'
taken a year later in 7/28/75 show no significant change. Differentials
obtained from Quadrilateral "D" which was purposely located away from
reservoir influence in Bridge Creek Canyon compares well with those
surveyed in Quadrilaterals "A," "B," and "C" located at the Bridge.
2. Rainbow Bridge Elevation Surveys
No significant change in elevation has occurred. The Colorado River
Storage Project Power Operations Office is preparing a summary report
relative to the triangulation (quadrilateral) surveys. This report
will explain survey systems, accuracies obtainable, and the location.
3. ~Ihittemore Strain Gage Instrur.lentation
A new set of measurements were made to evaluate deformation response
of the existing cracks in the Bridge legs. Appended to Status Report #4
was a measurement plot of Whittemore Gage readings showing accumulative
movement between the cracks responding to seasonal temperature variation.
Upon reaching a complete season temperature cycle it is found that the
movement registered across the cracks returned to the i ni ti a 1 poi nt.
4. Photogeology
A fourth phase of the photogeology system composed of 26 photographs
.coveri ng the Bri dge Creek Canyon and Rai nbol'l Ilri dge l'las taken on
August 13 when Lake Powell was at elevation 3673.70. Comparison with
other sets of photogeology maps taken for prior monitorings shOl'J no

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