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-6- <br /> <br />Spoil Density <br />Our firm has previous experience with measurement of density of spoil <br />materials aT other mines which operate under similar conditions and with <br />similar formational materials in The Moffat and Routt County areas. We have <br />performed large sand cone density tests and nuclear density tests within spoil <br />materials. We believe these tests are indicative of the materials found at the <br />Colowyo site. The tests have indicated loose spoil found near the surface of <br />dumped spoil has density ranging between about 90 and 110 pcf, with an <br />average of about 95 pcf. UJhere spoils have been partially compacted, density <br />ranges from 110 to about 125 pcf with an average of 115 to 120 pcf. <br />The mode for placing excess spoil at the Colowyo mine has been to use <br />comparatively thick lifts on the order of 50 to 100 feet. Spoi! is dumped <br />a and/or dozed off near the top of each lift and allowed to slide down an <br />advancing face as the spoil pile is enlarged. This procedure causes large <br />materials to slide down the face and create a comparatively permeable zone <br />at the bottom of each lift. The Streeter Canyon Fill was placed using these <br />methods without installation of a designed underdrain. Subsequent <br />groundwater monitoring wells installed in the Streeter Canyon fill have <br />indicated no development of free water has occurred within the fill over its <br />13 year (t) life. <br /> <br />