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;~ <br />Accordingly, the Division is requiring that Seneca Coal Company: <br />a. Identify the source and character of material which will be used for the <br />embanlanent and keyway construction. If this source is an on-site borrow azea, <br />a plan for treatment of .surface water runoff from the borrow area will need to be <br />developed and implemented. <br />b. Provide the Division with a demonstration that the foundational material beneath <br />the embankment is capable of supporting the embarilanent in order to achieve the <br />required 1.3 factor of safety. The demonstration should be based on laboratory <br />information (Field density and moisture, relative 'Proctor' moisture/density for <br />compaction control, size gradation for mechanical classification, and an <br />appropriate determination of shear strength) derived from analyses of a sample <br />of the foundational material. Particular care should be exercised to determine <br />mechanical characteristics at the moisture content encountered in the excavation <br />c. The approved permit committed on Exhibit 13~ to the installation of a horizontal <br />drainage system (Mirafi filter fabric wrapped granular layer) at "Embanlarrent <br />Base (if needed)". The Division suspects that this installation is needed. The <br />testing and analysis specified in 'b", above, should allow Seneca Coal Company to <br />complete the determination of drain necessity. The results of this determination <br />should be submitted to the Division for review and approval, prior to <br />implementation. <br />d. Provide the Division with a demonstration that the materials to be used to backfill <br />the keyway and to construct the embankment can be compacted to achieve a <br />strength which will meet the required 1.3 factor of safety. The demonstration <br />should be based on laboratory information ('Proctor relative moisture/density for <br />compaction control, size gradation for mechanical classification, and a <br />determination of shear strength) derived from analyses of a sample of the <br />proposed material. Particular care should be exercised to determine mechanical <br />characteristics at moisture contents being encountered in the excavation. <br />2. Page 13-3-12 of the approved Yoast mine permit application states that additional field <br />investigations will be conducted to determine embankment base (foundation) conditions. <br />The Division is not aware of Seneca Coal Company having conducted these <br />investigations. If these investigations have been conducted, please provide the Division <br />with the results. If an additional investigation has not been completed, Seneca Coal <br />Company should cease keyway and embankment construction operations until all <br />necessary site investigations, laboratory sample analyses, and stability analysis have been <br />completed. <br />3. Rule 4.05.6(13) of the Rules and Regulations of the Colorado Mined Land Reclamation <br />Board for Coal Mining (Rules) requires that ponds be examined regularly during <br />construction by a qualified professional engineer or other qualified individual under the <br />direction of the engineer. The Division has not seen a registered professional engineer <br />QmAu B. McG1(loh 2 August 7, 19RS <br />