FLOOD01607 - Laserfiche WebLink

Home Browse Search

..." - I I I I I I I I I I I I I I I I ~ A CENTRAL CITY MASTER DRAINAGE STUDY 34 Existing condition annual damage (risk) values are: Annual Damage ~ (damage) x probability of damage Eureka Gulch: ($4,293,200 x 2 x 0.05) x 1/2.6 = $165,100 ($1,343,800 x 2 x 0.05) x 1/2.6 = $ 51,700 = $216,800 Nevada Gulch: TOTAL Improved condition annual damage (risk) values are: Eureka Gulch: ($4,293,200 x 2 x 0.05) x 1/13 = $ 33,000 Nevada Gulch: ($1,343,800 x 2 x 0.05) x 1/13 = $ 10,300 TOTAL = $ 43,300 Therefore, the savings due to improvements are: Annual Damage Savings = $216,800 - $ 43,300 ~ $173,500 Annualized cost of construction, for comparison with the Annual Damage Savings, is calculated by amortizing the construction cost estimate (from Section 6, excluding Nevada and Spring Gulch tailings and slope stabilization, see Section 9). Assuming the cost of money to a public agency is five percent over 40 years (such as the CWCB construction fund), Annual Construction Cost ~ $519,800 x 0.08024 ~ $ 41,700 Therefore, annualized expenditure of $41,700 saves the community $173,500. This is compelling evidence of the benefit of drainage construction expenditure. This simplified study is conservative for several reasons: 1. damage to buildings and contents is limited to five ,percent, 2. many of the buildings are stores and restaurants and would experience greater damage, 3. additional factors such a,s loss of life, lost wages, etc. are not accounted for here, all of which increase the savings, and 4. no allowance is made for "historic" value of buildings. It could be argued that the majority of the benefit can be attributed to improvements to th~ major drainage systems on both Eureka and Nevada Gulches. However, the intent of the conceptual design is to maximize use of the existing drainage system, i.e., underground flumes and pipes, which is made possible by improvements to the local drainage facilities (area drains) . HydroDynamics Incorporated