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I I I I I I I I I I I I I I I I I I I CHAPTER IV IMP ROVEt1ENTS of maintenance on t'lese facilities. Eliminating major flooding by improving existing facilities to its full potential and using existing topographic features as much as possible is the most economical solution. Detention ponds in connection with existing and proposed parks and recreational areas are favored improvements because of the dual purpose they can serve. Proposed improvements along the drainage way of 1st Avenue Tributary are a combination of detention ponds and improved open channels. The existing 24 inch culvert starting at Benton Street cannot be improved for increased outflow. To prevent excessive buildup of storage with subsequent overflow into the Sheridan Blvd. depression a conduit in 1st Avenue is proposed. The conduit also eliminates costly improvements along the 1st Avenue drainageway east of Sheridan Blvd. A. GENERAL During Phase A of this study each tributary was divided into decision units. Tht,! decision units or reaches for Phase P are identical. The 1st Avenue Tributary was divided into jurisdictional reaches: Weir Gulch to Sheridan Blvd. (Denver); and Sheridan Blvd. to west of Jay Street (Lakewood). Th~ Dakota Avenue Tributary was divided into three reaches: Weir Gulch to Sherirlan Blvd.; Sheridan Blvd. to Harlan Street; anrl Harlan to Pierce Street. The Depew Street Basin was also divided into three reaches: Deoew to Harlan Street; Harlan to Lamar; Lamar to Pierce Street. The proposed improvements are described opposite eacl drawing. A general discussion of guiding philosophy during preparation of the preliminary design is given below. B. 1ST AVENUE TRIBUTARY Only minor hazards are associated with a lOO-year flood west of Depew Street. Between Depew and Benton Street the natural r1rainageway is encroached upon by land developers. At Benton Street the channel ends and an existing 24 inch diameter corrugated metal culvert is the only means of conveying runoff toward Sh'.'ridan Blvd. The small cul vert causes ponding and suhsequent overflow into Sheridan Blvd. Ponding in the depression of Sheridan Blvd. just north of 1st Avenue can he as deep as four feet and cause severe problems because of the function Sheridan Blvd. has as a major north-south traffic arterial. Between Sheridan Blvd. and Weir Gulch the main problems are undersized channels and culverts and lack C. DAi<OTA AVENUE TRIBUTARY ~'ajor problems must be anticipated during a DQ-year flood in tile upper portion of the trib~tary between Harlan and Pierce Streets hecause of proposed cOMmercial development sOllth and west of Villa Italia Shopping Center. During a 100-year flood the crossing of Sheridan Blvd. will overflow at a depth exceeding 1 foot with velocities approaching 10 feet per second, creating hazardous conditions for traffic on Sheridan 81vd. Requiring the developers of the area south and west of Villa Italia Shopping Center to provide detention ponds with a conduit limiting the outflow is absolutely essential for a balanced system of improvements along Dakota Avenue Tributary. Between liarl an Street and Sheri dan Blvd. an open channe 1 ~Ii th drop structures is proposed. East of Sheridan Blvd. a comhination of improvements TH 1