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HomeMy WebLinkAboutDrainage Reports - 01/22/1980GOLDEN MEADOWS FILING NO:-4 Final Drainage Study January 22, 1980 Prepared For: Medema Homes 5295-DTC Parkway Englewood, Colorado 80111 0 • GOLDEN MEADOWS #4 Final Drainage :.Study Table of Contents • • General Criteria Drainage Plan • Summary Appendix Vicinity Map • Intensity Duration Curve Street Capacity Curves Runoff Calculations • Inlet Capacities Detention Pond Sizin 9 • A B C D E F • • • GENERAL This project consists of 149 single-family attached and detached dwelling units. It is located in Section 31, Township 7 .Nor.th,- Range 68 West in the .City of Fort Collins, Colorado. It is bounded on the north and west by Golden Meadows Filing No. 2, on the east by the Dixon Canyon Lateral Irrigation Ditch, and on the south by presently undeveloped ground. CRITERIA This report follows criteria set forth in the Fort Collins Storm Drainage Design Criteria manual. The initial storm has been set as.. -the two year storm; and the major storm has been set as the 100 year storm. As the subdivision is less than 200 acres in size, the rational method has been used to calculate runoff. "C" values of 0.20 for undeveloped ground and 0.45 (RLP zoning) for developed ground have been utilized.. The C values for the 100 year storm have been modified by an antecedent moisture condition factor of . 1.25. DRAINAGE PLAN In general, flows generated in this project will flow southeasterly to the Dixon Canyon Lateral, where they will be carried via a storm sewer to the Collindale South Pond. Historically, all runoff from-f:L the site flowed to theirrigation ditch, but it is proposed that only the rear of lots bordering the ditch be allowed to continue to flow into the ditch, in sheet flow. Detention for this project will be completely satisfied by the Collindale South Pond, which detains flows from the entire area. However, piping the entire 100 year flow from the project under the irrigation ditch.itto.the pond would be prohibitively expensive. Therefore, it is proposed that two small detention ponds be constructed within the project boundaries to reduce the peak.flows to a level that can be reasonably handled. Calculations for these two ponds are included in the appendix. Construction of Golden Meadows No. 2 to the north and west has effectively eliminated all flows onto the project from those directions. Ground to the east slopes away from the project. Ground to the south, however, presently partially flows northerly to Filing 4's south boundary. It is proposed that these flows collected in a swale and directed easterly to the pond to be built at the southeast corner. When the ground to the south developes, r, Wheaton Drive will be extended easterly, roughly parallel to the south boundary. It is anticipated that Wheaton Drive will then intercept the majority of the area currently' -flowing onto Filing No.. 4's south boundary.. Flows in the streets within the project have been analyzed at critical points. Where the allowable street capacity is exceeded (at point 19) inlets are provided to collect the runoff in a storm sewer. Other inlets are provided:at sumps as indicated to collect and dispose of runoff. SUMMARY The proposed development creates no significant drainage hazards to itself or adjacent lands. Due to the flat ground, care must be taken to insure that runoff can be adequately carried. However, the proposed plan addresses those problems via detention ponds, adequate street grades, and storm sewers. 0 .i Pik A4, . -ay • _ 3 _ _ _ _..t'e '� _Jl ., v .. ,."�c�f� .. 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