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• 2. EXCESS SPOIL FILLS A. STREETER FILL Requirement Prior to 1994 Colowyo had been required to conduct subsidence monument surveys, piezometer well testing, certified inspections and reports on a quarterly basis. Technical Revision No. 26 submitted to the Division and approved on March 18, 1994, reduced these monitoring requirements. The current monitoring requirements require quarterly piezometer well testing and a spring and seep assessment. Monument surveys, certified inspections and reports will be completed only during the second calendar quarter. Results Refer to the 1997 Annual Report Map for details regarding the specific location of each survey monument and piezometer well location. A summary of survey data and associated diagrams, inspection reports and other information is provided in Exhibit 6. Streeter Excess Spoil Fill. 1. Survey Monuments -Fill Settlement -Two monuments are located at approximate 100' intervals from [he 6700' level to the 7200' level on the Fill for a total of twelve monuments The survey data suggests that the anticipated settling of the Fill material remains stable with little change. After initial settling during the first four or five years, analysis of the ongoing • monitoring data typically indicates no significant changes. Overall settlement ranges from 1.5 to 4.48 Feet (6800 N. Point) which is minimal considering the depth of the fill at the upper elevations (over 250 feet). During 1995 the 6700' level survey, monument data indicated that the elevation of the entire bench had risen almost .5 feet over the previous year. After further investigation we found that the north reference point located on the sandstone rock bluff had actually settled because of movement of the bluff itself. Because of this reference point settling the 1995, 6700' level data was in error. On May 31, 1996 Colowyo submitted a report to the Division summarizing the work to evaluate the 6700' reference point and reestablishment of anew point to monitor the three lower benches (6700, 6800, 6900) of the Fill using XYZ coordinates. Exhibit 6 contains a copy of the survey data and diagrams showing the initiation of the new methodology. The new survey technique summarizes the data similar to the summaries for the upper three benches. Apparently the 6700 reference point had been failing, slowly, for quite some time. Initiation of the new methodology indicated that the Fill had continued to settle, but due to • [he reference point also settling, [he bench movement was not picked up by survey. Overall 3