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<br />Case History <br /> <br />!. <br />I <br />, <br /> <br />In June, 1977, a residential subdivision developer in <br />Jefferson County dug a uti Ilty trench half way up a 100 foot <br />long slope contrary to the recommendations of an engineering <br />geology report. Surface water collected in the improperly <br />located and constructed trench causing a landsl ide 100 feet <br />across, 50 feet long and up to 6 feet deep. It is not known <br />If the costly remedial measures wi II prevent additional <br />sliding and damage to property in the subdivision. <br /> <br />Case History <br /> <br />A schoo I in Eag I e County was proposed for the toe of an 0 I d <br />landsl Ide. A geologic examination revealed natural hazards <br />and the location of the muiti-story school, footbal I field <br />and grandstand area was moved to a safe site. The estimated <br />savings: $3.5 mii I ion. <br /> <br />I <br />, I <br />I. <br /> <br />Case History <br /> <br />An area being planned as a subdivision in Summit County was <br />engulfed in a matter or minutes by a mudsl ide caused by <br />saturated soi Is below the Town of Breckenridge water <br />reservoir and a beaver pond. Geologic Investigation showed <br />severa I s i mil ar 5 I i des had occurred prev I ous I y. The property <br />lost Its prime value and extensive regrading and mitigation <br />work was required. No structures were involved. Rerouting <br />drainage, drying out the slope, regrading and preventive <br />construction measures should mitigate future damage as the <br />area is developed. <br /> <br />:= <br /> <br />,- <br /> <br />Case History <br /> <br />During heavy spring snowmelt In 1972, the municipal sewage <br />disposal plant for the city of Cortez was threatened by <br />sudden and massive "erosion" eating away at the bench upon <br />which the plant was located. Emergency action by City of <br />Cortez amp loyees prevented impend I ng severe damage to the <br />plant and appurtenant faci Ilties. <br /> <br />A geological stUdy of the site during the criSIS showed that <br />the actual cause was not normal erosion, as had been <br />originally supposed, but was a type of landsl iding known as <br />lateral spreading. A build up of groundwater developed <br />during the runoff caused a weak 501 I at a depth of about 20 <br />feet to liquefy. Outf low of the i Iquefied weak soi I at depth <br />caused collapse of overlying firm clays and the entire <br />mixture of firm clay, liquefied soi I, and water was washed <br />down the stream course by runoff waters, allowing the <br />process to continue.; <br /> <br />Proposed reconstruction and enlargement of the faci I ity <br />recognizes the potentially serious geologic problems and it <br />is being engineered to minimize the hazard. An eventual <br />savings in excess of a mi Illon dollars may be real ized. <br /> <br />29 <br />