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Ms . Camille Farrell <br /> March 15, 1989 <br /> Page 3 <br /> AMENDMENT NO. 3 STIPULATION COMPLIANCE INFORMATION (continued) : <br /> (2) Attached is a table of survey data for points established to <br /> monitor ground movement above the pits. The survey points <br /> are plotted on the enclosed plan map of Sunnyside Basin. <br /> PROBLEM AREAS: <br /> (1) Enclosed is a copy of the report sent to the Colorado Health <br /> Department on the reported spill at Tailings Pond #3 , <br /> March 3 , 1989. <br /> (2) On the attached plan map is a point marked "Approximate <br /> Location - Point of Intersection with Old Workings", located <br /> in the Sunnyside Pit floor . An old stope or raise was <br /> unexpectedly encountered, and at that point mininq was <br /> stopped. The depth of the hole and probable interconnection <br /> with larger underground stopes preclude the feasibility of <br /> filling the void. Because of the onset of winter , the hole <br /> was timbered over as a temporary safety measure until <br /> remedial action could be taken during the 1989 construction <br /> season. We propose to cover the hole with a reinforced <br /> concrete cap, and would like to know if that approach might <br /> be acceptable to the Division. Please inform me. <br /> (3) On the attached plan map is a point marked "Approximate <br /> Location - Little Mary Surface Subsidence" , located in the <br /> diversion trench south of the Lake Emma hole . Last fall a <br /> surface depression in the diversion trench was temporarily <br /> repaired by filling and installation of a "half culvert" <br /> suspended on cables to divert water over the affected area. <br /> It is assumed that this surface disturbance was caused by <br /> cavinq of a hanging wall gouge zone in a stope stopped over <br /> 200 feet below the surface. In order to reach the surface, <br /> the gouge zone must have channeled in a relatively <br /> restricted area or the cave would have choked itself off by <br /> filling the mined area. This type of caving is definitely <br /> not typical for the Sunnyside Mine, as most stopes exhibit <br /> very little tendency to cave when left open. However , this <br /> is the only explanation available for the surface <br /> subsidence. We propose to maintain the area by periodic <br /> filling and water diversion until subsidence stabilizes. We <br /> will then perform a permanent repair . Please advise me if <br /> this approach is acceptable to the Division. <br />