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i7 " . . Associates (TEA) reviewed and revised all previous studies. The Corps' original hydrology values were determined to be acceptable, and therefore all floodplain analyses and re- analyses used the Corps' hydrology values. . The existing FEMA Flood Insurance Study does not provide floodplain mapping for the Keewaydin subdivision, which is actually in the lOO-year floodplain, . Bill Taggart, under contract with the Urban Drainage and Flood Control District, determined that the hydraulic differences between his study, the G&O study, and the Love study are not substantial. The main differences seem to be in the magnitude of the split flows that occur at the Highway. In addition, the 500-year flow in the study area should really be larger than what the G&O study shows. . Bill DeGroot said that "phase 1" of the floodplain analysis by TEA is nearing completion. There will be a "phase II" study by TEA that will address further hydraulic and other issues. . Even if the levee is certified, there is still a flood risk to downstream residents due to the 100- year overflows into the Keewaydin subdivision. However, the subdivision has better flood protection with the levee than without it (assuming no levee failure). . Due to the mining of the property by the Flatirons company, the floodplain and topography has been substantially altered from the historic conditions. Approximately 4,000,000 cubic yards of fill would be needed to fill in the "hole" left by the mining activities. . The topo mapping for a portion of the floodplain area upstream of Highway 36 is inadequate. Ideally, new mapping (I' or 2' contours) would be needed to better analyze the floodplain. Other comments and issues . Boulder County is concerned about the hydrology on South Boulder Creek. According to the County, the peak flow values seem to be too low, and do not seem to be proportional to the Boulder Creek values. (The Corps of Engineers substantially increased the Boulder Creek peak flows to help justify a proposed flood control project on Boulder Creek a number of years ago). Bill DeGroot said that re-evaluation of the hydrology at this late time would substantially delay future master planning and floodplain study efforts, Larry Lang warned the County that peak flow values could possibly go down instead of up if the hydrology is re- evaluated. . Larry Matel said that Boulder County is not interested in rushing through the levee certification process. He also said that the County Commissioners will have to be educated and brought up to speed on all of the risks, options, and consequences of relevant levee issues. The Commissioners will have to be convinced about "what's the right thing to do" before any decisions are made. 3