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iii iiiiiiiiiiiii iii 999 SENECA COAL COMPANY SFNECA II-W MINE, PERMIT C-82-057 T-7 STOCRTANR AS-BUILT REPORT The T-7 stocktank was constructed in the fall of 1996. It is located in 006 Gulch just upstream from the inlet of HRC-A1, in the SEyiNW'/e of Section 22, Township 5 North, Range 88 West. The location of T-7 stocktank is shown on Exhibit 13-2, Surface Hydrology Map. All of the stocktanks at the Seneca II-W Mine will be constructed following the guidelines contained in Attachment 13- 11. An as-built survey of this structure was conducted on October 23, 1996. This survey generated the following statistics for stocktank T-7. Bottom of Pond Elevation - 7129.1 Spillway Elevation - 7135.4 Average Spillway Width - 10.0 feet Top of Embankment Elevation - 7138.7 Average Top of Embankment width - 20.0 feet Upstream Embankment Slope - 5.4H:1V Downstream Embankment Slope - 6.2H:1V Basin Elevation-Staae-Area-Capacity Table ELEVATION STAGE AREA CAPACITY DESCRIPTION (FT.-MSL) (FEET) (ACRES) (ACRE-FEET) 7129.1 0.00 0.00 0.00 BOTTOM OF POND 7131.0 1.90 0.00 0.00 7133.0 3.90 0.00 0.00 7135.0 5.90 0.00 0.00 7135.4 6.30 0.00 0.00 SPILLWAY 7136.0 6.90 0.00 0.00 7138.7 9.70 0.00 0.00 TOP OF EMBANKMENT 6.3 To the best of my knowledge and belief, based upon my professional expertise, and to the extent possible, stocktank T-7 at the Seneca II-W mine was constructed in accordance with prudent state-of-the- art earthen embankment construction. Further, the structure was constructed in compliance with the approved guidelines as specified in Attachment 13-11 of Seneca Coal Company's approved mine permit. Seneca will inspect the stocktank quarterly to evaluate structural integrity, storage capacity conditions, and remedial work requirements. Therefore, pursuant to Rule 4.05.6(10), the above is the T-7 stocktank as-built certification report. ~~ Michael G. Altavilla Colorado P.E. 28455 Date