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FLOOD08354
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Last modified
1/25/2010 7:14:20 PM
Creation date
10/5/2006 3:32:49 AM
Metadata
Fields
Template:
Floodplain Documents
County
Boulder
Community
Lafayette
Stream Name
Coal Creek , Waneka Reservoir
Basin
South Platte
Title
Major Basinwide Planning
Date
12/1/1980
Prepared For
Boulder County
Prepared By
Camp Dresser & McKee
Floodplain - Doc Type
Floodplain Report/Masterplan
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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />.' <br />I <br />I <br />I <br />I <br />I <br />I <br />., <br />I <br />I <br />I <br />I <br /> <br />slope and 4 to 1 sideslopes, Mannings n-valves used were .03 for a grass-lined <br />channel and ,016 for concrete channels. <br /> <br />arterial streets with the intent that 100-year flows would overtop the streets <br />by no more than 6-inches at the street crown, Ten-year culverts were also <br />designed along major drainageways passing under the Chicago, Burlington and <br />Quincy tracks, Ten-year designs were used at these crossings due to the <br />prohibitive sizes and costs of constructing one-hundred-year capacity culverts <br />by means of pipe-jacking. <br /> <br />All grass-l ined channel s were designed to flow at sub-critical depths, <br />Therefore, in reaches of major drainageways where the existing topography was <br />too steep, drop structures were designated, with a maximum drop at anyone <br />structure of 4-feet. The flow invert was maintained a minimum of 5-feet below <br />existing grade to permit efficient connection of local drainage systems to the <br />major drainageways. <br /> <br />Construction Cost Estimate <br /> <br />Underground conduits were used for drainageway reaches where channel s were not <br />practical. Conduits and culverts were designed to convey flows utilizing inlet <br />control allowing for a 20-percent blockage due to debris build-up at the <br />entrance. Headwalls and wingwalls are provided at inlets and outlets of <br />cul verts, in order to insure smooth fl ow transi t ions to and from connect i ng <br />channels. Manning's n-valves for concrete pipe and corrugated metal pipe were <br />assumed at .016 and .024, respectively. <br /> <br />The development of the construction costs for the selected alternative plan are <br />based upon the unit costs presented in the Phase A portion of this study, <br />adj usted 10-percent for i nfl at i on that is expected to occur between the two <br />printings. Table 5 presents the unit construction and maintenance costs used in <br />the cost estimate, All unit costs include labor and overhead for a particular <br />construction item, Detailed construction costs are presented on facing pages of <br />the major drainageway plans at the end of this report. These summaries include <br />costs of drainageway improvements, utility relocation, property acquisition, <br />operation and maintenance, engineering contingencies, legal, fiscal and <br />administrative costs. <br /> <br />The concrete channel shown on sheet 10 of 15 of the drai nageway pl ans was <br />designed with 2:1 side slopes, 1-foot of freeboard and a maximum of .6 percent <br />slope. This channel is proposed due to the limited right-of-way available to <br />convey the design flow. <br /> <br />Underground Conduits and Street Crossings <br /> <br />Design frequencies for street and railway crossings were established USing the <br />Storm Drainage Design and Technical Criteria for the City of Lafayette and <br />surrounding Boulder County as a guide. One-hundred year crossings were designed <br />along any major drainageway passing under South Boulder Road or North Weld <br />County Road and Flagg Drive. Ten-year culverts were designed at all other minor <br /> <br />22 <br /> <br />23 <br />
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