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_. <br />TO: DOUG BOWMAN <br />• FROM: TOM JOHANSEN J65-042 <br />SUBJECT: TUNNEL SEALI PLAN <br />DATE: 4/15/65 <br />• <br /> <br />The attached rock tunnel sealing plan is submitted in response to <br />the request from Mined Land Reclamation Division to comply with <br />stipulation No 4 of the Mining Permit. <br />The purpose of the sealing plan is to demonstrate how the tunnel <br />will be reclaimed upon completion of mining. Of particular <br />interest to Mined Land Reclamation is sealing the portions of the <br />tunnels that cross the Cozzette, Rollins and Middle Sandstones, <br />to prevent future mixing of waters, should these sandstones be <br />aquifers. The plan will also show how the portals will be sealed <br />to prevent water from entering onto the surf ace. <br />It is proposed that seven. sets, or a total of fourteen seals, be <br />constructed in the rock tunnel following abandonment of coal <br />mining in Coal Basin. The seals will be located as shown on <br />Sketch SK-1. _ <br />Seals No 1 - Portal openings <br />Seals No 2 - Below the Cozzette Sandstone <br />Seals No 3 - Above the Cozzette Sandstone <br />Seals No 4 - Below the Rollins Sandstone <br />Seals No v - Above the Rollins Sandstone <br />Seals No 6 - Below the Middle Sandstone <br />Seals No 7 - Above the Middle Sandstone •. <br />The seals in the portals will stop water from flowing out onto <br />the surface. The seals on each side of the sandstones will . <br />prevent ground water from cor;tacting other strata between the <br />seals and entering the mine openings. <br />The seal design is based on the assumption that the full length <br />of tunnel, between the seals, will be filled with water after <br />mining and the hydraulic head will return to its' pre-mining <br />level. From this assumption the maximum possible or worst case <br />force on the seals were calculated. • <br />A typical section of the tunnel, from Coal Basin to the North <br />Fork Valley, is shown in StG-l. The elevation diff ererices between <br />seals are shown. The mar.imum possible head occurs between seals <br />3 and 4. Hydraulic heads above the seals are caused by the <br />difference in elevation between the seals. A safety ,factor of <br />three was used to calculate the ultimate design force on the <br />seals. <br />43 _ <br />