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<br />B. PROPOSED SOLUTION <br /> <br />No Action <br />(ALTERNATIVE I) <br />Taking no action (the Do Nothing Alternative) to mitigate the flood hazard to Weldona will leave the <br />community vulnerable to the effects of future large storm runoff events, The costs of this alternative are the <br />health hazards and significant property damage as described in the preceeding section. These costs Can exceed <br />the cost of a flood mitigation effort during a single flood event. <br /> <br />Diversion ChanneI/Ring Levee Without Upstream Detention <br />(AL TERNA TIVE 2) <br /> <br />This alternative consists of construction of a channel and ring levee system on the north side of Weldona to <br />divert the storm flows around the community to the South Platte River. This system would be sized to <br />accommodate a 100-year runoff event. Reinforced concrete box culverts would be constructed to convey the <br />flow under Highway 144 to a new channel constructed south along Grove Street from Highway 144 to the <br />South Platte River. Bank protection would be provided along the South P:iatte River at the new channel <br />outfalL <br /> <br />The existing ditch and culverts along the south side of Highway 144 would be enlarged to accommodate the <br />road overtopping at the RCBC and the 100-year runoff from the small watershed consisting of Weldon a, Bank <br />protection structures would be constructed on Riverside Canal and Weldon Ditch to prevent future bank <br />failures. <br /> <br />The total estimated cost of this alternative is approximately $600,000. This estimate does not include costs for <br />final topographic survey and mapping, final engineering design, legal and administrative costs, and <br />construction management. <br /> <br />Detention ReseIVoir North of Weldon a <br />(ALTERNATIVE 3) <br /> <br />Alternative 3 consists of building a detention reservoir approximately 1.5 miles due north of the community of <br />Weldona. The main purpose of a detention facility is to store excess stOlm runoff in order to protect <br />downstream property and public infrastructure. The detention facility would capture storm water runoff from <br />the Schaefer Draw basin and spilled flows from the Riverside CanaL The Riverside Canal is just to the north <br />(upstream) of the proposed reservoir site. The dam embankment would be of earthen construction with a <br />maximum fill height of about 24 feet. The embankment would be vegetated with grass. and the upstream and <br />downstream side slopes would be no steeper than 3H to I V. The reservoir would be designed for 100-year <br />capacity and would include an emergency spillway that could pass up to the design 100-year discharge. The <br />emergency spillway is located to act as a side-channel spillway that would not allow flows to pass over the <br />dam embankment. The proposed spillway configuration is generally more cost effective, especially given the <br />terrain of the project area. The estimated storage volume is on the order of 400 acre-feet, and the surface area <br />at maximum capacity is approximately 55 acres. Maximum reservoir outflow would be limited to about 150 <br />cfs, Downstream channel improvements and other facilities are not proposed as part of this alternative. It is <br />assumed that the reservoir outflow would follow natural drainage paths, and the flow would end up as shallow <br />sheet flow across agricultural fields and open space areas. <br /> <br />-14- <br />