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<br />P.R. Fletcher & Associates, Inc., and in an addendum to that report <br />dated January 14, 1992 (Reference 18). <br /> <br />As a result of the revised analysis, the BFEs, floodplain and <br />floodway boundary delineations, and zone designations were modified <br />along West Lake Channel and West Lake Channel North Tributary. <br />Topographic work maps at a scale of 1:1,200, with a contour interval <br />of 2 feet, produced by P.R. Fletcher & Associates, Inc., and dated <br />January 10, 1992 (Reference 19), were used to develop the new <br />boundaries as shown on FIRM Panel 0020. Table 3, "Floodway Data," <br />and Flood Profile Panels 30P and 31P were revised. This revision <br />removes the information shown in the Floodway Data Table and the <br />Flood Profiles from Cross Section J to Lowell Boulevard for West <br />Lake Channel and from Cross section A to Cross Section B for West <br />Lake Channel North Tributary. The Flood Profile for West Lake North <br />Tributary (previously Flood Profile Panel 28P) was deleted. <br /> <br />This revision also incorporates a LOMR dated May 16, 1996. The LOMR <br />was based on the effects of levee and channel improvements along <br />West Lake Channel and is shown on FIRM Panel 0020. This revision <br />affects the area along West Lake Channel from West 128th Avenue to <br />approximately 1,600 feet upstream of the intersection of King Circle <br />and Westlake Drive. A Conditional LOMR was issued for the project <br />on January 23, 1995. <br /> <br />The revised hydrologic analysis was performed by P.R. Fletcher & <br />Associates, Inc., using the UDSWM2-PC computer program for West Lake <br />Channel from the Gay Reservoir Channel to the Trails at Westlake <br />Detention Facility. The UDSWM2-PC is the personal computer version <br />of UDSWM2, the Runoff Block of the Environmental Protection Agency <br />Storm Water Management Model (Reference 3). The revised hydraulic <br />analysis was performed by McLaughlin Water Engineers, Ltd., Inc., <br />using the USACE HEC-2 computer program (Reference 20). Cross- <br />section data for the revised analysis were obtained from topographic <br />maps and field-survey information and the starting water-surface <br />elevation was taken from the original study. Roughness coefficients <br />(Manning's "n" values) ranged from 0.02 to 0.05 and were similar to <br />the original study. The results of these analyses are presented in <br />the report entitled "Request for Conditional Letter of Map Revision <br />(CLOMR) for West Lake Channel Improvements, Westlake Village Filing <br />No.6, Broomfield, Colorado," prepared by McLaughlin Water <br />Engineers, Ltd., and dated March 1994 (Reference 21). <br /> <br />As a result of these revisions, the elevations and floodplain and <br />floodway boundary delineations were modified along West Lake Channel <br />from West 128th Avenue to approximately 1,600 feet upstream of the <br />intersection of King Circle and Westlake Drive. The increases in <br />BFEs are contained in the channel. From approximately 1,200 feet <br />upstream to approximately 1,600 feet upstream of the intersection of <br />King Circle and westlake Drive, the base flood is contained in an <br />underground pipe. <br /> <br />Topographic work maps at a scale of 1:600, with a contour interval <br />of 1 foot, produced by McLaughlin Water Engineers, Ltd., and dated <br />December 1993 (Reference 22), were used to develop the new <br />boundaries as shown on revised FIRM Fanel 0020. Table 3, "Floodway <br />Data," and Flood Profile Panels 29P, 30P, and 3lP were revised. <br />This LOMR also corrected the representation of the corporate limits <br />for the city of Broomfield. <br /> <br />34 <br />