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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />REACH 2 (North Tributary - Upper Limit to Main Street) <br />The area drained by the North Tributary is presently being developed by <br />Broomfield County Club. The first filing has been constructed, and a deten- <br />tion facility has been installed upstream of the Community Ditch. Outflows <br />frOm the detenti on pond are di rected to Ni ssen Reservoi r. A di versi on wall <br />and 100-year channel are proposed for construction with future fil ings for <br />the subdivision. The proposed channel will carry flows from Nissen Resevoir <br />southward across the golf course to a point north of East 10th Avenue. <br /> <br />The subbasins tributary to Reach 4 are largely developed as single-family <br />residential. The obvious floodplain encroachment by the development along <br />East 7th Avenue is the most serious flood hazard problem in the entire basin. <br />During a major flood event, East 7th Avenue becomes the main drainageway, <br />carrying flows at sufficient depths to affect most of the residences along <br />7th Avenue and areas immediately adjacent. The channel downstream from Birch <br />Street is sufficient to carry the lOa-year flow of 1,450 cfs, but this flow <br />will overtop Midway Boulevard with depths in violation of UD&FCD criteria. <br />Upstream from Sheridan Boulevard, lOa-year flows will spread out in a wide <br />floodplain due to the flat topography in the area. Low density single-family <br />residential development is currrently planned for this area and a lOa-year <br />channel is planned to convey flows to Sheridan Boulevard. <br /> <br />REACH 3 (Main Street to East 10th Avenue) <br />The main channel combines with the North Tributary just downstream from Main <br />Street and traverses the golf course to East 10th Avenue, flowing through two <br />small ponds and crossing the Equity Ditch. An l8-inch pipe carries the nor- <br />mal trickle outflows from the golf course ponds. Major flows would breach <br />the pond embankments and overtop East lath Avenue, where the existing culvert <br />has capacity to handle less than a 2-year flood. <br /> <br />REACH 5 (Sheridan Boulevard to Mobile Home Park) <br /> <br />The channel through Reach 5 is a 1 arge fl at swa 1 e wh i ch travels across a <br />large open field. Subbasins immediately tributary to this area are undevel- <br />oped and land use is agricultural. There are at present no flood hazard pro- <br />blems in Reach 5. <br /> <br />The most serious effect of a major flood event along Reach 3 would be the se- <br />vering of a major east-west transportation route by a washout of the road <br />surface and embankment at East lath Avenue. <br /> <br />REACH 4 (East 10th Avenue to Sheridan Boulevard) <br />Downstream from 10th Avenue, the channel flows through a farm pond and then <br />across a large bpen field':to East 7th Avenue in the form of a large swale <br />,. C:', " <br />with no defined low floweharrni!L Low flows are carried beneath East 7th <br />Avenue by a 24-inch diameter pipe,,9u~fall ing at Birch Street. The area <br />between Bi rch Street and Mi dway Boulevard has been developed as a si ngl e <br />famlly residential subdivision and a,lOO-year capacity grass-lined channel <br />has been designed to carry flows to Midway Boulevard, A double 7-foot by <br />5-foot concrete box culvert has been installed at Midway Boulevard with total <br />capaci ty' of approximately 660 cfs ,compared to the 100-year flow of 1,450 cfs <br />at this location (without upstream detention) . The existing channel travel s <br />southward from Midway Boulevard in a natural channel which jogs to parallel <br />Sheri dan Boul evard until it reaches the twi n cul vert pi pes carryi ng flows <br />eastward beneath Sheridan Boulevard. <br /> <br />REACH 6 (Mobile Home Park to Lowell Boulevard) <br />A man-made channel carries flows southward between the mobile home park and <br />an existing sewage lagoon embankment and then eastward along the park's south <br />property line. The channel then flows through a small nursery pond and con- <br />tinues to Perry Street. Downstream from Perry Street the channel is heavily <br />overgrown with trees and brush to its confluence with the channel from the <br />City Park Basin, from which point it continues to Lowell Boulevard through a <br />sparsely forested area. <br /> <br />Development in this area is confined to the mobile home park and the nursery, <br />although the City Park Basin, which interfaces the study basin in this area, <br />contains some industrial and commercial establishments nearby along 120th <br />Avenue. The primary flood hazard problem along Reach 6 is in the mobile home <br />park/sewage 1 agoon area. Major flows can sp 1 it and flow across the 1 agoon <br /> <br />7 <br />