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SENECA COAL COMPANY SENECA II-W MINE, PERMIT C-82-057 T-24 STOCRTANR AS-BUILT REPORT The T-24 stocktank was constructed in the fall of 1996. it is located near the outlet of HRC-G2, in the Swl/NE~ of Section 9, Township 5 North, Range 88 west. The location of T-24 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-24. Bottom of Pond Elevation - 6686.6 Spillway Elevation - 6692.3 Average Spillway Width - 14.5 feet Top of Embankment Elevation - 6692.8 Average Top of Embankment Width - 11.0 feet Vertical Height of Dam (Upstream Toe to Spillway) - 4.3 feet Upstream Embankment Slope - 3.9H:1V Downstream Embankment Slope - 4.6H:1V Basin Elevation-Stage-Area-Caoacity Table ELEVATION STAGE AREA CAPACITY DESCRIPTION (FT.-MSL) (FEET) (ACRES) (ACRE-FEET) 6686.6 0.00 0.00 0.00 BOTTOM OF POND 6688.0 1.40 0.01 0.01 6689.0 2.40 0.02 0.02 6690.0 3.40 0.03 0.05 6691.0 4.40 0.05 0.09 6692.0 5.40 0.06 0.15 6692.3 5.70 0.07 0.17 SPILLWAY 6692.8 6.20 0.09 0.21 TOP OF EMBANKMENT To the best of my knowledge and belief, based upon my professional expertise, and to the extent possible, stocktank T-24 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-24 stocktank as-built certification report. I~~:~~~i~HT.~'Fa~,, F E 6 2 4 1997 Michael G. AL~avt4~~a Colorado P `•.28455 Date l