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• The £ormetions which are most abundant at or near the surface <br />in Weld County are the Fox Hills and Laramie formations. <br />Refer to the Generalized Stratigraphic drawing on the <br />following page. The Ogallala and Arikee formations ere found <br />in the northeast portion of the county. The alluvial <br />materials were deposited in the flood plain of the South <br />Platte River Valley. Terrace deposits formed mainly in the <br />central portion of the county on both sides of the river <br />valley. <br />4.4.3 Geologic Structures <br />Pre-mine bedrock structures consist of gently undulating <br />bedding planes with a regional dip of 10-3o to the <br />west-southwest, with a north-northwesterly strike. <br />No mayor faulting patterns exist on the site. Random <br />"fracturing" of plastic bedrock materials exist due to stress <br />release as the strata was unloaded. Several discontinuous <br />randomly oriented shear zones have been encountered during <br />mining. <br />Please refer to Section 4.5.4, Hydrologic Data for cross <br />sections of geology. <br />4.4.4 Geologic Hazards <br />• No geologic hazards are present at the Keenesburg Mine - ash <br />disposal site. Topography of the dump site will be nearly <br />flat, and due to the highly permeable mantle of send that <br />surrounds the proposed disposal area, erosion potential is <br />minimal. The Keenesburg Mine has not discharged or received <br />run on within its permit area due to henvy precipitation <br />episodes since the inception of the mine in 1980. <br />Although the materials present at the Keenesburg mine eah <br />disposal site have relatively low strengths associated with <br />them, these materials will not be required to meet engineering <br />criteria regarding slope stability and subsidence. <br />• <br />-11- <br />