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(7ANSEI� Ll/JAN & AA_SV`'IATII(N <br />ItOrogeological and Environmental Consultants <br />Figure 1 <br />According to Mr. Bachofer, the lower level of the house has repeatedly flooded since <br />August 2004, when the flows at the Fort Lupton Gauge reach 6,400 cubic feet per second <br />(cfs), whereas in the past the flows reached over 10,000 cfs and no flooding occurred <br />(GL&A, 2013). The elevation of the door on the bottom level floor has been surveyed by <br />a licensed surveyor and is at 4875 feet above mean sea level elevation (amsl). The 100 <br />year flood plain level determined by Weld County for obtaining a Flood Hazard Permit <br />on 5/19/1987 was 4874.0 feet and as such Mr. Bachofer was not required to have a permit <br />because his land was above the 100 year floodplain level. There was also no history of <br />flooding on this property prior to this time. <br />HEC -RAS Modeling <br />Surface water modeling of the South Platte River adjacent to the Bachofer property was <br />performed using the HEC -RAS model to simulate the hydrologic impact of aggregate <br />mining on flows in the river and its direct impact on the Bachofer property. The HEC - <br />RAS model, developed by the US Army Corps of Engineers, is designed to perform one- <br />dimensional hydraulic calculations on a full network of natural and constructed channels <br />(U.S. Army Corps of Engineers, 2010). <br />-3- <br />