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I I I I I I I I I I I I I I I I I I I 18 averages 610 feet in width, channel velocities average 6 feet per second, and overbank velocities average 3 feet per second. The reach is platted as the Millbrook subdivision but no dedicated right-of-way exists for drainage. Reach seven of SJCD (South) extends from Ken Caryl Road to the Section 27-28 line. Independence Street will be overtopped and failure is likely for floods greater than or equal to the two year flood. When the South Kipling Street extension is constructed it will cross SJCD (South) at Independence Street. The average 100-year flood plain width is 340 feet, the average channel velocity is 5 feet per second and 2 feet per second is the average overbank velocity. The fourth reach extends from Depew Street through South Kendall Boulevard. The drainageway passes through the Columbine Hills park located within the Columbine Hills subdivision. A nearly adequate channel exists within this reach. Drainage difficulties are due to the overtopping at Kendall Boulevard and backup from the overflow at South Depew Street. Kendall Boulevard will be overtopped during floods larger than the 5 year event. During major flows, Kendall Boulevard could fail and overland flow will occur over a park and school yard just down- stream, landscaping and fence damage could occur at five homes, and flow will extend down West Elmhurst Avenue. The 100-year flood plain width averages 410 feet, channel velocities average 8 feet per second, and overbank velocities average 2 feet per second. Reach eight of SJCD (South) extends from the Section 27 line to the upstream limit of study. No road crossings presently exist. The 100-year flood plain averages 160 feet in width, channel velocities average 5 feet per second, and overbank velocities average 2 feet per second. Reach 1 of Tributary No. 1 of SJCD (South) extends from the confluence with SJCD (South) to South Carr Street. The drainageway passes through the Columbine Knolls South subdivision and no drainage problems are known to exist. The 100- year flood plain averages 110 feet in width, channel velocities average 7 feet per second, and overbank velocities average 2 feet per second. No dedicated drainage right-of-way exists. The fifth reach extends from Kendall Boulevard to the confluence with Tributary No.1. Flood flows will overtop South Pierce Street without failure for floods greater than or equal to the 10 year event. No existing buildings are threatened by the 100-year flood within this reach. The 100-year flood plain width averages 210 feet and channel velocities average 8 feet per second. OVerbank velocities average 5 feet per second. The drainageway passes through the Columbine Knolls and Columbine Hills subdivisions. A 100 foot right-of-way exists between Kendall Boulevard and South pierce Street only. The second reach of Tributary No. 1 extends from the downstream side of South Carr Street through South Garrison Street. The drainageway passes through the Fairview Heights subdivision across numerous lots without a dedicated right- of-way. A total of nine existing roadway crossings will be overtopped and will probably fail for floods greater than the 2 year event. They include South Carr Street, South Carr Court, South Cody Street, South Dover Street, South Dudley Street, South Estes Street, South Estes Court, South Everett Street and South Garrison Street. Two other roadway crossings are platted but are not con- structed. One building could be damaged during the larger floods. The 100- year flood plain width averages 190 feet, channel velocities average 3 feet per second, and overbank velocities average 1 foot per second. The sixth reach extends from the confluence with Tributary No.1 through Ken Caryl Road. Ken Caryl Road and Estes Court could both fail due to overtopping by the 2 year frequency flood or greater. The structure and contents of one home could be damaged and the downstream end of the culvert under Wadsworth Boulevard has become silted. The 100-year flood plain width averages 200 feet, while channel velocities average 6 feet per second. Overbank velocities average 3 feet per second. Within this reach the drainageway passes through or near the subdivision of Columbine Knolls Estates, Columbine Knolls South, Ken Caryl Acres, and Fairview Heights. In the Ken Caryl Acres subdivision, a 40 foot easement is provided for utili~ies and drainage. No other dedicated right-of-way exists. The upstream limit of the sixth reach is also the upstre~ limit of the drainage master planning study for SJCD (South). Tributary No.2 of SJCD (South) has two reaches. The first extends from the confluence with SJCD (South) to the Section 33-34 line. It is presently unplatted although the plans exist for a subdivision called The Meadows. within this reach Ken Caryl Road would be overtopped with possible failure during floods as large as the 2 year event. No other drainage problems are known to exist. ~ Leonard Rice Consulting Water Engineers, Inc.