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1 I '1 I I 1 I I' 1 I I 1 1 1 1 1 I I I I its tributaries; these crossings also tend to constrict the channel and create potential for detention, flooding of adjacent property and overtopping of roadways during major storm events, Within this basin, several detention ponds/storage areas exist which may provide for a reduction in stormwater runoff. Within the Tri-Town Basin, the Tri-Town Drainageway (also known as Biederman Draw or the McCormick Seep Ditch in its nortjlern most reach) is the most predominant drainage feature, traversing the central portion of the basin in a northerly direction. Similar to the Godding Hollow Basin, several minor tributaries exist within the watershed to collect and convey stormwater runoff into the drainageway. Numerous county roads, state highways and irrigation canals cross the drainageway and its tributaries; these crossings tend to constrict the channel and create potential for detention, flooding of adjacent property and overtopping of roadways during major storm events. In the upper portion of the basin, there is no significant existing detention storage on either the major drainageway or its tributaries.' The Saint Vrain River, which defmes the northern boundary of both basins, represents the second notable drainage feature in each basin, The river receives all the stormwater runoff that is generated within the watersheds. The lOG-year floodplain associated with the Saint Vrain River encompasses less than 5 percent (950 acres) of the total drainage area within both basins, Four irrigation ditches, the Last Chance Ditch, the Rural Ditch, the Godding Ditch, and the Coalridge Ditch (also known as the Severance Ditch or the Boulder Ditch), also traverse the Godding Hollow and Tri-Town Basins, These ditches convey irrigation flows within the basin but offer limited value as drainage features that will convey stormwater runoff out of the basin. Due to the limited capacity of the ditch systems coupled with the magnitude of the stormwater flows, these irrigation ditches do not represent a drainage boundary within the basin. The drainage features along with the limits of the 100-year floodplain associated with the Saint Vrain River, Godding Hollow and Tri-Town Drainageway are presented on the existing drainage facilities map provided on Sheet l. 2.3 Description of the Major Drainageways 2,3,1 Godding Hollow Draina.geway The Godding Hollow Basin consists of a predominantly rural watershed with a well-defmed major drainage channel. The major drainageway originates near the intersection of WCR 7 and WCR 8. From this location, the Godding Hollow Drainageway conveys stormwater runoff under a 42-foot wide timber railroad bridge located approximately one-half mile southwest of the WCR T:\OPEMCoweldOJlcoweldOl fnl rpt. wpd 2.3 Septembu 8, 1999