Orestimba Creek Feasibility Study - Stanislaus County

More documents

Recommendations

Info

Economics Appendix – Draft Report - Orestimba Creek Feasibility Study, Stanislaus County, California – September 2012 6.1.3.1 Alternatives Carried forward from Preliminary Screening for Further Evaluation As a result of the preliminary screening, the following alternatives were carried forward for additional, more detailed, analysis and optimization as they appeared to have the highest incremental net benefits. Locations for these alternative measures are shown in Figure 6-1. No Action Chevron Levee (Farm Rd.Levee) Chevron Levee + Channel Modifications (Hybrid 3) Figure 6-1: Location of the Chevron Levee and Channel Modifications 34
Economics Appendix – Draft Report - Orestimba Creek Feasibility Study, Stanislaus County, California – September 2012 6.1.4 Optimization of the Chevron Levee Height The chevron levee height was optimized by inserting incrementally higher levees into HEC-FDA and comparing the increased benefits to the estimated incremental costs. Costs were estimated by Cost Engineering for a levee equal to the mean 2% (1/50) annual chance WSEL and the mean 0.5% (1/200) annual chance WSEL + 3ft. These two values were then used to create a linear interpolation between the two points in order to estimate the cost of incrementally higher levees. These costs include only those costs that are variable depending on the height of the levee (mostly fill material). The index point used for this incremental analysis was the Stuhr Rd. and CCID canal intersection, so the benefits here appear higher than those reported in the without project chapter of this report, but this is due to the rating curve and stage uncertainty as discussed above in section 5.5. The final benefits used for economic justification will be based on the without project conditions as summarized in Table 5-5. In addition, costs reported here do not reflect Total Project First Costs, instead these costs represent only those variable costs in relation to levee height. Total Project First Costs can be found in Table 7-1. This analysis is solely used for optimization of the levee height in order for costs and residual benefits to be determined in more detail on only one plan. As shown in Table 6-2 below, the optimal elevation for the top of levee at this index point is determined to be around 112.75 feet, which equates to a levee 5.5 to 8 feet tall depending on the ground elevation changes along the levee alignment. It is noted here that this height is higher than the mean 0.2% (1/500) WSEL, but because of the alluvial fan type of flooding, the mean 0.2% (1/500) WSEL is only 9 inches higher than the mean 2% (1/50) mean WSEL. 35
Page 1 and 2:
Economics Appendix - Draft Report -
Page 3 and 4:
Page 5 and 6:
Page 7 and 8: Economics Appendix - Draft Report -
Page 57: Economics Appendix - Draft Report -
Page 109 and 110:
Page 111 and 112:
Page 113 and 114:
Page 115 and 116:
Page 117 and 118:
Page 119 and 120:
Page 121 and 122:
Page 123 and 124:
Page 125 and 126:
Page 127 and 128:
Page 129 and 130:
Page 131 and 132:
Page 133:
show all

Orestimba Creek Feasibility Study - Stanislaus County

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?