Orestimba Creek Feasibility Study - Stanislaus County

Economics Appendix – Draft Report - Orestimba Creek Feasibility Study, Stanislaus County, California – September 2012
Long-term risk provides the probability of having one or more damaging floods over a
period of time.
Assurance is the probability that a target stage will not be exceeded during the
occurrence of a specified flood.
Project performance statistics for each impact area is displayed by impact area for both without
and with project conditions in the tables below.
Table E- 8: Project Performance – With Project Conditions – Rural EIA
Alternative
Annual
Exceedance
Probability
Median
Expected
10 Year
Period
Long-Term Risk
30 Year
Period
50 Year
Period
Assurance by Events
10% 2% 1% 0.20%
1. No Action 24.31% 24.22% 94% 99% 99% 6% 2% 1% 1%
2. Chevron Levee at
112.75ft
3. Chevron Levee at
114.8ft
24.31% 24.22% 94% 99% 99% 6% 2% 1% 1%
24.31% 24.22% 94% 99% 99% 6% 2% 1% 1%
Table E- 9: Project Performance – With Project Conditions – Urban EIA
Alternative
Annual
Exceedance
Probability
Median
Expected
10 Year
Period
Long-Term Risk
30 Year
Period
50 Year
Period
Assurance by Events
10% 2% 1% 0.20%
1. No Action 14.43% 15.13% 81% 98% 99% 13% 0% 0% 0%
2. Chevron Levee at
112.75ft
3. Chevron Levee at
114.8ft
0.01% 0.04% 0% 1% 2% 99% 99% 99% 98%
0.00% 0.00% 0% 0% 0% 99% 99% 99% 99%
ES.7
Net Benefit Analysis
With benefits calculations complete, annual costs need to be derived to complete the benefit cost
analysis. Economic feasibility and project efficiency are determined through benefit cost
analysis. For a project or increment to be feasible, benefits must exceed costs and the most
efficient alternative is the one that maximizes net benefits (annual benefits minus annual costs).
ES-xiv