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1 <br /> upstream of U.S. Highway 36 adjacent to the Flatiron Property, utilizing FTS hydrology to <br /> ' more clearly define the limits of the 100-year floodplain in the vicinity of the property. <br /> This analysis will be detailed in a second report entitled "Floodplain Analysis of South <br /> ' Boulder Creek at the Flatiron Property in Boulder, CO" to be completed in August, 1996. <br /> This hydraulic modeling effort will analyze the Flatiron Property under two conditions: <br /> ' Condition 1 - 100-Year Floodplain Model which incorporates a 200-foot wide interceptor <br /> channel and no flood levee and Condition 2 - 100-Year Floodplain Model which includes a <br /> FEMA Certified Flood Protection Levee. <br /> Site Perimeter Berm <br /> As was noted above, a site perimeter berm was constructed as a pan of the flood <br /> protection for the gravel mine on the Flatiron Property. This berm was reportedly <br /> ' constructed by excavating the existing soils down to the shale bedrock. The bean was <br /> then created by the placement of overburden materials so that the top of the berm would <br /> ' be a minimum of 1-foot above the 100-year water surface. The gravel mine operators, as <br /> a part of the reclamation plan, are currently raising the height of the berm in several <br /> ' locations in an attempt to insure that the berm has a FEMA required minimum of 3-feet to <br /> 3.5 feet of freeboard (excess elevation above the 100-year water surface). Currently, <br /> certain portions of the berm are in excess of 5 feet above the regulatory 100-year water <br /> surface (southern area) while other areas on the eastern edge of the property are below the <br /> MI,inirnum FEMA freeboard requirement. Reclamation operations including elevating the <br /> ' lower portion of the berm continue as of the date of this report. <br /> ' The 1986 FHAD prepared by G&O assumed that the site perimeter berm provided flood <br /> protection to the area west of the berm. The 1980 mapping used in the FHAD indicated <br /> ' that a berm was in existence surrounding the mining operation but was not questioned as <br /> to its viability as an acceptable FEMA flood protection levee. <br /> ' -11- <br />