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RULE 4 PERFORMANCE STANDARDS <br />4.09 Disposal of Excess Spoil and Underground Development Fill Waste <br />Colowyo originally constructed the excess spoil fill known as Streeter Fill in accordance with Section <br />2.06.2, Experimental Practices Mining. The details of this alternative spoil disposal practices are set forth <br />in Section 2.06.2. <br />On March 3, 1986 Colowyo submitted a request to the Division for a Technical Revision to change the <br />status of the Streeter Fill Experimental Practice. The request was to change the Streeter Fill to an excess <br />spoil fill designed and constructed under the alternative design standards set forth in Rule 4.09. (3). All <br />the monitoring requirements of the fill will remain as originally approved to insure the stability <br />requirements of Rule 4.09 are met. <br />The Division approved the revision on August 18, 1986. <br />For further details regarding this Technical Revision and the history of Streeter Fill, refer to Section 2.06, <br />Special Categories. <br />In December, 1993, Colowyo proposed a Technical Revision to the Division to reduce the monitoring <br />requirements for Streeter Fill. During the 1993 — 2006 period, the following monitoring plan was <br />implemented: <br />Streeter Fill Monitoring and Inspection Plan for Streeter Fill (199 -2006) <br />1) Colowyo conducted monitoring of the 12 Streeter Fill survey monuments once a year, during <br />the second calendar quarter of each year. For a location of the twelve survey monuments <br />(6700 N and S through 7200 N and S) and the baseline reference monuments (AH -21, RP -2 <br />and SRP -3) refer to Drawing 30A — Revised Streeter Fill As- built The revised Drawing 30A <br />is intended to update the Permit only with respect to 1) the Streeter fill survey monuments, 2) <br />baseline reference monuments and 3) the wells (W6900N, W6900S and W6700). The <br />original Drawing 30 — Streeter Fill Design and As Built will remain in the Permit and serve to <br />represent all other aspects of Streeter Fill. <br />2) Colowyo monitored water level in the Streeter Fill piezometer well (W6700) and conduct a <br />spring and seep survey quarterly. <br />3) In the event that the water table in the piezometer well rises to a level greater than 10 feet <br />above bedrock, Colowyo agreed to notify the Division within 2 working days and to complete <br />a survey of the twelve subsidence monuments and report the results to the Division within <br />one month. <br />4) Colowyo completed an annual inspection of the Streeter Fill each year of this time period <br />during the second calendar quarter by a registered engineer. This inspection included a <br />specific examination of items 1 and 2 above and included a discussion of the facial conditions <br />of the fill in order to determine whether the development of perched water tables within the <br />fill was affecting its surficial slope stability. <br />5) The monitoring reports and certified inspection reports are available during inspections by the <br />Division but were only submitted to the Division in the Annual Reclamation Reports. <br />On 9/9/97 monitoring of the 6900 well indicated that the steel casing had failed at the 114.3' level <br />allowing water from a pre- existing perched water zone to enter the well at that level. Subsequent <br />Rule 4 Performance Standards 4.09 -1 Revision Date: 8/3/10 <br />Revision No.: MR -102 <br />