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ij City 0/ Littleton If'~ ~~ r-.l.assey D"C!'N Cln(l SleD lSoutnJ Map Draln.age'N2Iy Plannng Update Concep!U31 Desl9n Repoo Fet>I"lJ<'lry 2006 , Reach 4 - Kendall to Pierce: Low flow check structures are proposed to control headcutting. The structures would have a 3.loot maximum drop, with a predicted 0.4% slope between the structures. Approximately 550 linear feet of vertical banks are proposed to be reshaped with 3 to 1 (horizontal to vertical) side slopes. Reach 5 - Pierce to Wadsworth: Approximately 700 linear feet of vertical banks are proposed to be reshaped with 3 to 1 (horizontal to vertical) side slopes. A 4-loot high sloping drop structure and low flow check structures are proposed to control headcutting. The structures would have a 3-foot maximum drop, with a predicted 0.4% slope between the structures. Cleaning out the culverts under Pierce Street and the adjacent channel is proposed to improve the function of the culverts. culvert is proposed to replace the existing culverts at Carr Street to reduce the street overtopping and eliminate one house from the floodplain. Acquisition of a drainage easement is recommended. SJCD (South) Tributary No.2: There are no improvements proposed on Tributary NO.2. SJCD (South) North Tributary Reach 1 - South Platte Reservoir to South Platte Canyon Road: There are no improvements proposed along this reach. Reach 6 - Wadsworth to Carr: A 6-foot high sloping drop structure is proposed upstream of Wadsworth to reduce the channel slope and control erosion. Low flow check structures are also proposed to control headcutting. The structures would have a 3-foot maximum drop, with a predicted 0.4% slope between the structures. Approximately 700 linear feet of vertical banks upstream of Wadsworth are proposed to be reshaped with 3 to 1 side slopes. The culvert and adjacent channel under Wadsworth are proposed to be cleaned out to improve the function of the culvert. Reach 2 South Plane Canyon Road to Sheridan Court: Between Sheridan Court and South Platte Canyon Road, low flow check structures are proposed to control headcutting. The structures would have a 3-foot maximum drop, with a predicted 0.4% slope between the structures. Reach 7 Carr to Ken Carvl: Acquisition of a drainage easement east of Carr Street is recommended. A 5.5-foot high sloping drop structure and low flow check structures are proposed to control headcutting. The structures would have a 3.foot maximum drop, with a predicted 0.4% slope between the structures. Reach 3 Sheridan Court to Ken Carvl: There are no improvements proposed along this reach. It is recommended that elevation certificates be obtained for the seven houses that appear to be in the 100-year floodplain between Sheridan Court and Ken Caryl Avenue to ascertain whether they are in the floodplain. Reach 4 - Ken Carvl to Pierce: Low flow check structures are proposed between Newland and Pierce streets to control headcutting. The structures would have a 3-foot maximum drop, with a predicted 0.4% slope between the structures. Reach 8 - Ken Carvl to Kiptina: Acquisition of a drainage easement is recommended. Development of the property between Kipling and Independence Street was occurring at the time this report was published. It appears that a portion of the development is encroaching into the floodplain. The old Independence Street embankment is overtopped during the 100-year storm. It is recommended that the property owner take steps to protect the embankment from failure when it is overtopped. 6.3 General Recommendations In addition to the Master Plan improvements, it is recommended that Jefferson County, the City of Littleton, and other jurisdictions having land use powers within the planning watershed consider the following: Reach 9 - Kiplina to Ute Meadows School: It is recommended that the floodplain be preserved in this reach. A 9-foot high Sloping drop structure and low flow check structures are proposed to control headcutting. The structures would have a 3-foot maximum drop, with a predicted 0.4% stope between the structures. SJCD (South) Tributary No, 1 1. Take steps to stabilize all major waterways when their watersheds urbanize, to rehabilitate existing degraded reaches of waterways and their tributaries, and to aggressively control erosion and sediment transport during construction activities. 2. Require new land development, significant redevelopment and publicly funded projects to provide, to the maximum extent practicable, runoff volume control practices (i.e. infiltrating BMP's) whenever site conditions permit. 3. Require that all BMP's for all new development, significant redevelopment and publicly funded projects provide a Water Quality Capture volume (WQCV) as recommended in the Urban Drainage Criteria Manual - Volume 3, after accounting for volume reductions achieved using volume control practices. 4. Monitor land-use changes and, whenever the land-use changes result in imperviousness ratios that exceed the projections identified in the Final Plan, take steps to further limit increase in stormwater runoff through the use of additional on-site detention, infiltration BMP's and WQCV BMP's, thereby reducing runoff rates, volumes and future damage potential to the Final Plan levels. 5. Continue to implement their floodplain management regulations, including regulation of the 1 OO'year jloodway and floodplain, 6. Adopt a policy, if not already done so, of preserving the defined floodplains as open spaces to the maximum extent possible and provide at least 1-100t freeboard above the 1 GO-year flood Reach 1 - Confluence to Wadsworth: Low flow check structures are proposed to control headcuning. The structures would have a 3-foot maximum drop, with a predicted 0.4% slope between the structures. A 48.inch reinforced concrete pipe culvert improvement is proposed to be added to the existing culvert at Wadsworth Blvd. to eliminate the street overtopping. Reach 2 - Wadsworth to Carr: No improvements are proposed along this reach. Reach 3 - Carr to Garrison: A 4.5-100t high sloping drop structure, a 3.5-foot high sloping drop structure, and low flow check structures are proposed to control headcuning. The structures would have a 3-foot maximum drop, with a predicted 0.4% slope between the structures. Creating cul-de- sacs on Dover and Cody streets is proposed to create an open channel for Tributary NO.1 and remove four houses from the 1 OO-year floodplain. One 10-foot wide x 4.foot high reinforced concrete box 0\ 6-6