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 Why are Geologic Maps Important?Title Page In addition to the many uses of geologic maps noted in the previous section, geologic mapping will continue to be important because it is cost effective. For example, looking only at the avoidable costs associated with the cleanup of landfills and industrial disposal sites, the Illinois State Geological Survey documented a benefit-to-cost ratio that ranged from 5:1 to 54:1 for geologic mapping. The U.S. Geological Survey also conducted a rigorous assessment of the value of new geologic mapping in Loudoun County, Virginia and found net positive benefits considering just two uses of the map information (for siting a new landfill and a new highway). Similar assessments in Kentucky show the benefit-to-cost ratio of geologic mapping there to be 50:1. Rigorous benefit-to-cost studies have not been done in Utah. However, a single example here points to the value of geologic maps. We know, for example, that new geologic maps of the St. George area more accurately show the location of the region's infamous bentonite clay (known locally as "blue clay"), which is responsible for numerous foundation problems, and other geologic hazards that engineers and planners are now addressing. Given the myriad uses to which a map is put over its lifespan, the true benefit-to-cost ratio of geologic mapping must be greater still. On the flip side of the coin, the failure to use geologic maps or understand the geology of an area can lead to a variety of adverse land-use impacts: from catastrophic failure of dams such as the collapse of Quail Creek south dike in Washington County on January 1, 1989; to ground-water contamination at countless thousands of sites across the nation; to literally paving over valuable sand and gravel deposits needed to sustain urban growth, just to name a few.
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