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ELEVATION <br />NTS <br />Block seal at least <br />8 inches thick <br />constructed to meet <br />MSHA requirements per <br />30 CFR, Sect. 75.171 1 -2. <br />2.05-52 <br />Water Trap at Lower Permanent Seal of East Portal Required By MSHA <br />for Release of Water Behind Seals. <br />