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I I I I' I i I I I I I I I I I I I I I I 10/1-25 intersection. At WCR 10, runoff passes under the road in a single reinforced box culvert (2'Hx3.5' W) Runoff is then directed to three reinforced box culverts (two 6'Hxll'W) and one 6'Hx14'W) which are utilized to convey the flows beneath both lanes ofI-25 while a 60-foot wide timber bridge is utilized at the east frontage road. From the ]-25 frontag~ road, the channel continues northeast combining with three minor tributaries, north of the 'Colorado National Speedway complex. At this location, the major drainageway conveys stonnwater northward to the crossings of Coalridge Ditch and State Highway 52 where runoff is detained by the canal and road embankments which incorporate crossing structures consisting of two reinforced box culverts ( 7'Hx7'W and 8'H x 8'W). North of State Highway 52, a major unnamed tributary draining approximately 2, 170 acres west ofI-25 converges with the main channel of Godding Hollow. The main channel continues north for approximately three miles before passing under the Godding Ditch flume. The steel flume spans 60 feet of the Godding Hollow floodplain. Approximately one-half mile north of the Godding Ditch, the Godding Hollow channel confluences with the Rural Ditch. The Rural Ditch continues northeast for approximately one-quarter mile at which point turns north in a wasteway to the Saint Vrain River. During large flood events, Godding Hollow Basin runoff will break out of the Rural Ditch, combine with out of bank Tri- Town Basin runoff and proceed over land to the Saint V rain River. In summary, the major drainageway crosses one railroad, ten major county and/or state roads, four canals, and numerous other minor roads and utilities. Minor erosion of the Godding Hollow channel is evident at several locations and is typically associated with livestock watering and access. Erosion is also visible at several road crossings and where fanning practices have over-steepened the channel banks, In general, active erosion of the channel bed and banks is not prevalent throughout the basin. The Godding Hollow channel and floodplain are not heavily encroached with vegetation, The vegetation species vary from rangeland grasses and shrubs to willows and large deciduous trees occasionally intermingled with dense stands of wetland grasses and shrubs. Sheet 1 presents an illustration of the major drainageway and major crossing structures within the basin along with the location of the major tributaries to Godding Hollow. A detailed , description of the existing detention facilities/reservoirs, conveyance facilities and major road crossings, is provided in Chapter 3. 2.3.2 Tri-Town Drainageway The Tri-Town Basin consists of a predominantly rural watershed with approximately 1,5 square miles of urban development in the upper portion of the watershed, A well defined major T:IQPENlCoweld[)llcoweldOJ fnl rpt. wpd 2.4 September 8, 1999