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Table 3 Floodwater Retarding Structure Costs " " -------------------------------------------------------------------- Earth Dike System Struct Volume 10 of Fill CY Canst Cost $ '/ Eng Cost $ '/ proj Admin $ 3/ Land Rights $ (/ Total Instal $ 0'" Cost $ '/ A system of dikes to keep the 100-year frequency flooo within the Pawnee Creek channel would be impractical. The intent of the dike system proposed herein is to prevent flood waters from encroaching on the Riverside Cemetery and the Town of Sterling. This system of dikes would be installed at three locations, see figure 5, and would continue to allow overflow to occur at several locations along the Pawnee Creek channel as well as along u.s. Highway 6 and the Burlington Railroad. These out-of-bank flows would be restricted from moving to the northeast towards Sterling. -------------------------------------------------------------------- p" N P-3 N p-, P-6 P,' 796307 248481 694901 1122804 694640 680517 674083 2747259 857259 2397408 3873674 2396508 2347784 2325586 384616 120016 335637 542314 335511 328690 325582 467034 145734 407559 658525 407406 399123 395350 Total 4911733 16945479 2372367 2880731 225000 60000 135000 141000 90000 93000 138000 3823909 1183010 3275605 5215513 3229425 3168597 3184518 882000 23080577 13736 4286 111987 19368 11983 11739 11628 -------------------------------------------------------------------- 84727 Data pertaining to the three dike segments are shown in the following table: 11 Canst cost is engr est (which is $3.00/cy) + 15% cont ~ $3.45/cy 21 14% of const cost 31 17% of const cost 41 $300. per acre 5/ 0.5' of canst cost Location Earthfill - Length Concrete - Length (Ft.) (Cu. Yd.) (Ft.) (Cu. Yd.) West Dike East Dike 1/ South Dike 5350 2400 m Note: These are very preliminary cost estimates; however, they are sufficient to suggest a project of this magnitude may not be cost effective in terms of benefit-cost relationships. 14500 15340 3374 '" m Total 8655 33214 '" 620 I " I , , ------------------------------------------------------- 1/ East Dike has additional special structure to prevent flow north dONn highway and railroad. The West Dike would prevent a segment of out-oi-bank flow from moving overland to the northeast towards the Riverside Ce~etery and Sterling. The East Dike would promote more efficient use of the bridges on Pawnee Creek at U.s. Highway 6 and the railroad. The highway and railroad would be used as an emergency spillway to the South Platte River. This dike would prevent out-Of-Channel flows from following the highway and railroad towards Sterling. The dike would extend some distance below th~ railroad to prevent out-of- bank flows from encroaching onto a farmstead along the northeast bank. The South Dike would be near AtWOOd and would prevent northeast bound flows from following the highway and railroad to combine with the Main Pawnee Creek. These Atwood flows would be pushed over the highway and railroad to join the South Platte River. The following table shows an estimated cost of the proposed dike system. Figure 5 shows the flow pattern with the proposed dikes in place.