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<br /> <br />Case History <br /> <br />In June, 1977, a residential subdivision developer in <br />Jefferson County dug a uti I Ity 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 landslide 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 />landslide. A geologic examination revealed natural hazards <br />and the location of the multi-story school, football field <br />and grandstand area was moved to a safe site. The estimated <br />savings: $3.5 million. <br /> <br />Case History <br /> <br />An area being planned as a subdivision in Summit County was <br />engulfed In a matter or minutes by a mudsllde caused by <br />saturated soils below the Town of Breckenridge water <br />reservoir and a beaver pond. Geologic Investigation showed <br />several simi lar sl ides had occurred previously. The property <br />lost its prime value and extensive regrading and mitigation <br />work was required. No structures were Involved. Rerouting <br />drainage, drying out the slope, regrading and preventive <br />construction measures should mitigate future damage as the <br />area is developed. <br /> <br />Case History <br /> <br />During heavy spring snowmelt in 1972, the municipal sewage <br />d I sposa I p I ant for the city of Cortez was threatened by <br />sudden and massive "erosion" eating away at the bench upo~ <br />which the plant was located. Emergency action by City of <br />Cortez emp loyees prevented impend i ng severe damage to the <br />plant and appurtenant faci IItles. <br /> <br />A geological stUdy of the site during the crisis showed that <br />the actual cause was not normal erosion, as had been <br />originally supposed, but was a type of landsl iding known as <br />1 atera I spread I ng. A bu lid up of groundwater deve loped <br />during the runoff caused a weak sol I at a depth of about 20 <br />feet to liquefy. Outf low of the liquefied weak sol I at depth <br />caused co 11 apse of over I y I ng firm clays and the ent I re <br />mixture of firm clay, liquefied soi I, and water was washed <br />down the stream course by runoff waters, allowing the <br />process to continue.$ <br /> <br />Proposed reconstruct i on and en I argement of the fac ill ty <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 million dollars may be real ized. <br /> <br />29 <br />