FLOOD06961 - Laserfiche WebLink

Home Browse Search

I I I I I I I I I I I I I I I I I I I <Ii City of Littleton Massey Draw and SJCD (South) Major Drainageway Planning Update Conceptual Design Report February 2006 Reach 7 - Kiplina to Continental Divide Road: Ken Caryl Ranch Master Association owns the property along this reach. It crosses established greenbelts and parks. The channel appears to be stable, Reach 6 - Wadsworth to Carr: This reach flows through the Columbine Knolls South Estates Greenbelt. Portions of the channel are deeply incised, with vertical banks between nine and twelve feet high. Other portions of the channel are not as incised. The average slope within the reach is 1,6 percent. SJCD (South) crosses under Wadsworth in one 12-foot by 8-foot box culvert. SJCD (South) Reach 1 - South Platte Park to S. Platte Canyon Road: This reach is within property owned by the Centennial Water and Sanitation District. Drainage will flow through a new channel that was designed to carry the Probable Maximum Flood (PMF) of approximately 30,000 cubic feet per second around the future South Platte Reservoir. Construction of the channel was completed in 2005. The large PMF channel was designed with a low flow channel having a slope of approximately 0.5 percent and four drop structures, Under existing conditions, four out buildings appear to be in the 1 OO-year floodplain due to overtopping of S, Platte Canyon Road, Reach 2 - South Platte Canvon Road to Depew: This reach comprises the Millbrook Greenbelt. A low-flow trickle channel was constructed in this reach, which has an average slope of 0.7 percent. SJCD (South) crosses under South Platte Canyon Road in one 10-foot by 4.3-foot box culvert. The Columbine Trail crosses the channel. The trail is frequently overtopped and debris collects at the culvert inlet, posing a maintenance problem for the Foothills Park and Recreation District. South Platte Canyon Road is estimated to overtop 0,3 and 0.9 feet during the 5- and 1 OO-year storm events, respectively. It is estimated to overtop between the 2- and 5-year storm events, Reach 7 - Carr to Ken Carvl: Within this reach, SJCD (South) flows through private property. The average slope of the channel is 1.5 percent. Vertical banks with heights between three and six feet exist. SJCD (South) crosses under Carr in two 10-foot by 4-foot box culverts. Carr Street is estimated to overtop 0.1 foot and 2.0 feet during the 5-year and 1 OO-year events, respectively, It is estimated to overtop between the 2- and 5-year storm events, One house and two out buildings appear to be in the 100-year floodplain, Reach 8 - Ken Carvl to Kiplina: SJCD (South) flows through land owned by Jefferson County, the Stony Creek Terrace Home Owners Association, and private citizens. 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 segment between Ken Caryl and Garrison contains three drop structures and has an average slope of 1,3 percent between the drop structures. A concrete low flow channel and one large drop structure exist in the segment between Garrison and Kipling. The average slope of this segment is 1,5 percent. SJCD (South) crosses under Ken Caryl in three 8-foot by 5-foot box culverts and under Garrison in one 8-foot by 4-foot box culvert. Garrison Street is estimated to overtop 1.0 foot during the 1 OO-year event. It is estimated to overtop between the 25- and 50-year storm events, Reach 3 - Depew to Kendall: SJCD (South) flows through Columbine Hills Park in this reach. The average slope of the reach is 1.0 percent. At least a portion of the channel is edged with boulders. Vertical banks of less than three feet high exist within this reach. SJCD (South) crosses under Depew Street in two 12,5-foot by 5-foot boxes and two 6-foot by 3-foot box culverts. Depew Street is estimated to overtop 1.2 feet during the 1 OO-year event. It is estimated to overtop between the 25- and 50-year storm events. Reach 9 - Kiplina to Ute Meadows School: This reach is comprised of Sledding Hill Park and is characterized by stable slopes and banks, A series of ponds exists on the western portion of the reach. The overall slope of the reach is 2.2 percent, however, drop structures exist between the ponds and in the area of South Lee Way. SJCD (South) crosses under Kipling in one 8-foot by 8-foot side- tapered sloping inlet box culvert. One out building appears to be in the 1 OO-year floodplain. Reach 4 - Kendall to Pierce: This reach is within the Columbine Sports Park. The overall slope is 1.3 percent, however several grade control structures exist along the channel. It is believed that the original subdivision developer installed the structures. Most of the channel is lined with boulders. Between the central portion and the east end of the reach, significant degradation has taken place. Incised channels with vertical banks of 6 to 9 feet high exist. One grade control structure has been undermined and failed. Ball fields are located adjacent to the incised portion of the reach. The corridor along the channel is narrow and has fairly steep slopes. SJCD (South) crosses under Kendall in three 10-foot by 5-foot box culverts. Kendall Street is estimated to overtop 1.3 feet during the 100- year event. It is estimated to overtop between the 10- and 25-year storm events. Two out buildings appear to be in the 1 OO-year floodplain. Reach 5 - Pierce to Wadsworth: SJCD (South) flows through Wayside Meadows Park. The average slope of the channel is 1.3 percent within this reach. The channel had meandered at the east end, which was corrected by an UDFCD maintenance project in 2003, The channel contains low-flow grade control structures and one drop structure at the east end. Vertical banks with heights of three to six feet are present in portions of the reach. SJCD (South) crosses under Pierce in two 8-foot by 6-foot box culverts. Pierce Street is estimated to overtop 1.7 feet during the 100-year event. It is estimated to overtop between the 10- and 25-year storm events. SJCD (South) Tributarv No.1 Reach 1 - Confluence to Wadsworth: SJCD (South) flows through Wayside Meadows Park, with an average channel slope of 2.0 percent. Channels with vertical banks 3 to 6 feet high exist in this reach. Reach 2 - Wadsworth to Carr: This reach flows through Coronado Park, is stable, and appears to be relatively flat, although the overall slope is 2,0 percent. Wetlands are present within the reach. Two well-armored trail crossings act as grade control and a drop structure is present at the west end. SJCD (South) Tributary NO.1 crosses under Wadsworth in one 72-inch reinforced concrete pipe (RCP) culvert. Wadsworth is estimated to overtop 1.2 feet during the 1 OO-year event. It is estimated to overtop between the 25- and 50-year storm events. Reach 3 - Carr to Garrison: SJCD (South) Tributary NO.1 flows through private property in this reach with an average slope of 2,2 percent. The channel is heavily vegetated in the eastern portion of the reach and less vegetated and more incised in the western portion of the reach, with bank heights between 0 and 3 feet. The channel crosses under several streets within this reach: under Carr in three 36-inch RCPs, under Cody in one 36-inch RCP, under Dover in one 28-inch RCP, under Estes Court in one 44-inch RCP, and under Estes Street in one 60-inch CMP and one 48-inch CMP. The estimated overtopping depths and frequencies are shown in Table 6. 0\ 4-3