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I I I I I I I I I I I I I I I I I I I I Mr, Davi d Burke November 15, 1979 Page Two The general topographic setting is that of gently rolling pine covered topo- graphy which has been cut by fairly recent streams, High mountain terrain surrounds the general area, Of course, during the last hundred years this general topography has been much modified due to mining activity and, to a lesser extent, due to the building of new homes. This has resulted in much timber ha vi ng been cut with many hi 11 si des still beari ng only remnant stumps of conifer forests, The mining activity is much in evidence, especially in the nOI'thern most of the three tracts in the form of numerous shafts, both active and abandoned, with many more prospect pits dotting the country side and small to large tailings piles accompanying these. There had been much less mining activity in the smaller of the two land use areas and that seems to have been restricted to the northwest corner, The third tract south of Leadville which may be used for solid waste disposal has almost no mining activity. Very 1 ittle bare bedrock is exposed in any of the three areas, except in higher adjacent hillsides such as Ball Mountain or Little Ellen Hill or in some of the deeper stream-cut gulleys, NORTHERNMOST LAND USE AREA - Evans Gulch - This is the largest of the three areas and also the one which has been most heavily mined, There is still some evidence that present mining is going on just west of this tract and it was not clear from my reconnaissance whether mining is presently occurring. In the past the following minerals have been mined over the entire area: silver, lead, bi smuth, manganese, zinc, cadmium, barium, sulfur, f10urspar, pyrite and 1 ime- stone and dolomite. I n the southern port i on of the tract, between Yankee Hi 11 and Ball r'lountain, tungsten, gold, copper and iron haye been mined, It is my opinion, with the increased prices of silver, gold and other metals, that this area has a strong potential for renewed mining activity. In fact, many of the tailings could be reworked since early mining activity included high grade production in which marginal deposits were either overlooked or thrown out with "aste mateda]. For this reason any long range planning should certainly in- clude site specific mineral evaluations, or at least, an intensive search into available literature of past and present mining activities in the immediate areas, Of course once an area has been conmitted to sub-division or industrial use, mineral production becomes a less viable alternative. As previously mentioned, Pa1ezoic rocks crop out throughout this tract with older Palezoic rocks to the west and younger ones to the east, These formations have been intruded by Laramide-age rocks and the accompanyi ng mineral deposit i on has resulted in extensive mining wit"in the area, For this reason, there will be a high subsidence hazard potentional in this area because of the extensive underground mining which took place. f10st of the mining activity took place highet' up hillsides; therefol'e, most development should be concentrated in the 10Vler regions of this tract excluding the areas shown on the accompanying map as floodplain areas, landslide areas, or rock fall areas. In addition, the faulted areas should be avoided whenever possible although these will only be a problem in the event of a significant earthquake in this part of Colorado, an infrequent occurrence, Another reason for avoiding the steeper hillsides is that further landsliding is a possibility especially in the even of extraordinarily wet spring til~es or periods of extensive rainfall during the summer which may trigger netl sl ides, The old sl ides present indicate that this is a real pos- sibility, Site specific studies should be conducted in these areas to be certain that the hazards are totally avoided or properly mitigated, A-9 ,