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• 2. EXCESS SPOIL FILLS A. STREETER FILL Requirements 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 Mazch l8, 1994, reduced these monitoring requirements. The current monitoring requirements require quarterly piezometer well measurements and a spring and seep assessment on the face of the fill. Monument surveys, certified inspections and reports will be completed only during the second calendaz quarter. Refer to Exhibit 9 - 1999 Annual Report Man for details regazding 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 5, Streeter Excess Snoil Fill. 1. Survey Monuments -Fill Settlement -Two monuments are located at approximately 100' intervals from the 6700' level to the 7200' level 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 yeazs, analysis of the ongoing monitoring data typically indicates no significant changes. Overall settlement ranges from 1.5 to 4.72 feet (6800 N. Point). 2. Survey Monuments -Lateral Movement - Similaz to settling, lateral movement remains stabilized. Lateral movement has stabilized at generally less than two feet overall and, with the exception of the 6700' level, in an easterly direction. 3. No springs or seeps have been noted on the face of the Fill. 4. Piezometer Well -The 1997 Annual Reclamation Report provides a summary of the failure of the Streeter fill North well in 1997 due to a steel casing perforation located at 114.3 feet. During 1998, Minor Revisions 48 and 49 were approved by the Division to install an additional piezometer well on the 6700' bench of the Fill. On October 13, 1998 the W6700 well was completed into and through the underlying rock underdrain. Water was encountered corresponding to the vicinity of the rock underdrain suggesting that there was no development of a perched water zone within the Fill. This well was monitored during 1999 and indicated no change. Water levels were encountered at the 95.35 to 99.0 foot depth. The older wells located on the 6900 bench were left in place for possible monitoring, but no formal monitoring was proposed. During 1999 the 6900 bench deep well was checked four times during the year. In-flow through the casing perforation remains relatively constant. • 4