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I I I I I I I I I I I I I I I I I I- I Steele Street CrO$sing The existing CMP culverts under Steele Street are not adequate to pass the 100-year flood flow without modification. Additional discharge capacity can be achieved by either raising the street or by adding culverts. Both of these methods would be very costly. By adding dikes along the channel near Steele Street the culvert capacity is adequate to pass the 50-year flood flow without overtopping the road. During JOO-year flood conditions, Steele Street will be overtopped; however, most of the overflow will go directly across the roadway returning to the creek channel with very little flooding. It was concluded, therefore, to design the Steele Street to pass the 50- year flood flow and to allow the loo-year flow to overtop the roadway. York Street Crassing The existing York Street crossing is adequate to pass the JOO-year flood flow without overtopping the roadway; therefore, no modification is required. York Street to ExploradorCalle - Plates 111-4 and 111-5 Channel Design The existing channel in this reach is within the right-of-way owned by Adams County. The soil in the area consists of a 4 to 6 foot thick strata of sandy cloy (CL) underlain by fine grained sand (SM). The channel is unlined for approximately 2,100 feet upstream of the York Street bridge. The remaining 700 feet of channel, extending to the Explorador Calle bridge is partially concrete lined. The existing channel in th is reach has 0 toto I drop of about 22 feet in 2,800 feet or about 8 percent. Three drop structures in the unlined portion of this reach were washed out and moderate damnge to chan- nel banks and invert occurred during the /licy 5, 1973 flood. The concrete lined portion of this reach Functioned with no apparent damage except that the down- 111-4