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I I I I I I . I I I I I I I I I I -9- The reach from Montview Boulevard to Colfax Avenue, which runs through a mobile home court and other commercial develop- ments, represents one of the major problem areas on Granby Ditch. No major channel exists through this reach. The storm sewers carry only a small percentage of the 100-year discharge. The area from 1-225 to Crystal and Clark Streets and from Montview Boulevard to about one-third of a mile north of Colfax Avenue, is undated by the 100-year flood with depths ranging from one to three feet and velocities averaging about two-feet per second. flow line along Granby Street and along the drainage easement north of Granby Street has been constructed. This storm sewer carries only a small portion of the 100-year flood, approximately 100 cfs, with the remainder of the flood waters flowing down the center of Granby Street and the drainage easement upstream from K-Mart. The excess flows are generally confined to the street with depths ranging from two to three feet. As a result of site grading, six houses on Granby Street, south of 13th Avenue, are within the 100-year flood plain. There is also one house in the flood plain at the northwest corner of 12th Place and Chambers Road. This home is located in the low point and will probably be flooded by even minor storms exceeding the capacity of the existing storm sewer. Much of the commercial area south of the mobile home court and west of Sable Boulevard, along Colfax Avenue will be subject to shallow flooding during a 100-year flood. A major portion of the mobile home court east of Sable Boulevard will also be flooded. These flooding problems are caused by the inadequate culvert under Colfax Avenue and East Montview Boulevard. Water overtopping Colfax drains in a northwesterly direction causing the shallow flooding problems shown on Sheet 9. Flooding problems also exist south of Colfax Avenue and east of Sable Boulevard, where a portion of the 100-year flow, approximately 100 cfs, is conveyed in the existing road side ditch to low areas around the Mr. Plywood store. The reach from Colfax Avenue to the outlet of the two 48-inch concrete culverts near K-Mart, Station 85+00, is presently undeveloped. The channel has been adequately maintained along the south side of the K-Mart development and will convey the 100-year flood. The reach from Chambers Road to the inlet of the 42-inch storm sewer at 8th Avenue extends through residential develop- ment. A storm sewer has been constructed along Chambers Road, Chambers Court, and Hannibal Drive and has a capacity of approx- imately 100 cfs. The location of this facility is shown on Sheet 11 of the drawings. As the storm sewer system carries only a small portion of the total 100-year discharge, Chambers Road, Chambers Court and Hannibal Drive are all flooded to depths of up to five feet inundating homes on either side of Hannibal Drive. Along Chambers Court and Chambers Road, one apartment building is also inundated. The reach from K-Mart to Chambers Road is all residential. A 48-inch concrete storm sewer extending beneath the street The next reach from 8th Avenue and the storm sewer inlet to the upstream limits of the study at Laredo Street is undeveloped. Below the Highline Canal, in this reach, the flood plain is confined to undeveloped land. However, two homes located upstream from 8th Avenue could be subject to flooding from water spilling over the Highline Canal embankment. Also, many more homes not shown as being flooded could be inundated if failure of the Highline Canal were to occur. The Highline . I