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APPENDIX D <br />March 2000 -6- 993-2099.150 <br />uncertain were preferentially drilled), and will precipitate added conservatism in <br />undertaking future exploratory investigation and remediation activities. <br />The search of the files at the Cresson site for all of the mining plan maps in the area was <br />done in a very comprehensive manner, and no significant discrepancies were identified <br />between drawings. Based on this, the composite mine plan is felt to provide an accurate <br />and comprehensive depiction of the underground workings beneath Phase IV. While the <br />process of maintaining accurate mining records over a very long period of time is such that <br />additional workings may be present underground and not depicted in the plan, the <br />probability of this is considered small. <br />A topographic survey of the area was undertaken by Western States Surveying Inc. <br />• (WSSI). A plan showing topographic contours, which identifies some of the shafts and <br />surface dumps that were identified as part of the topographic survey, was prepared and this <br />information is shown in Drawing Nos. 3 and 4. <br />Many of the disturbance features observed on surface are cone-shaped shallow surface <br />mines typically about 25 feet in diameter and about 10 feet deep. The sides of the mines <br />are comprised of soil and rock fragments. Subsequent excavation of the mines indicated <br />that many were old shafts (based in part on the observation of timber reinforcements or <br />working levels which extended from the shaft) in which the unsupported surficial soils had <br />bridged across the shaft, or sloughed into the shaft. Some of the features in the Phase IV <br />area are collapsed portals of adits that historically provided access to the underground <br />workings. <br />C. <br />1:199UMFINAL REPORT2099APPD.DW Golder Associates