DuPage County East Branch DuPage River Resiliency Project. Benefit Cost Analysis

Transcription

1 DuPage County East Branch DuPage River Resiliency Project Benefit Cost Analysis 1.0 Benefit Cost Analysis Preparation The BCA for this proposal was a collaborative effort between DuPage County, V3 engineering consultants, and the US Army Corps of Engineers (USACE). The vital inputs for determining the economic value were provided by the county and the county s consultants. These inputs were then provided to an economist from USACE (Chicago District). 2.0 Proposal Cost Please see Exhibit E for budget information. 3.0 Project Area Conditions About 204 structures of varying use are located within the proposed project area. Each of these structures was assigned a depth-damage function, based on the structure use, and a structure value, based on HAZUS data. Table Lisle Structure Summary Structure Category Structures Values in Lisle Structure Count 1 Average Structure Value 2 Total Structure Value Residential 167 $ 91,100 $ 15,214,200 Commercial 16 $ 430,700 $ 6,891,600 Other 21 $ 104,100 $ 2,185,300 Total 204 $ 119,100 $ 24,291,182 1 This represents the all of the structures within the project footprint 2 Derived from HAZUS data based on 2010 census The existing flood risk to the project area is fairly significant. Most of the project area is cut-off from the East Branch or St. Joseph s Creek by levees, which can overtop between a 0.04 and 0.25 frequency event (25-40 year recurrence interval). About 107 of the 204 structures in the proposed project area are expected to experience first floor flooding at the 0.01 frequency event (100 year recurrence interval).

2 Table Inundated Structures Summary (existing condition) Structure Category Structures Inundated by Water Surface Elevation 10 yr 25 yr 50 yr 75 yr 100 yr 200 yr 500 yr Residential Commercial Other Total This is an estimate of structures with first floor inundation by water surface elevation Damages to structures and contents were prepared by comparing the modeled water surface elevations to the developed structure inventory. Based on the existing condition, structure and content damages are estimated to be $5.11 million at the 0.01 frequency event (100 year recurrence interval). Table Existing Damages to Structures and Contents Structure and Content Damages Recurrence Interval Annual Chance Exceedance Without Project Damages $ $ $ $ 644, $ 3,579, $ 4,487, $ 5,111, $ 5,287, $ 5,761, $ 8,811,900 Notes: The damages are based on water surface elevations, assessor and HAZUS structure information, and USACE depth-damage functions 4.0 Project Description Key differences between plans 1- Levee (all) vs Levee (west) and elevation (east) 2- Development of land organic vs induced development 5.0 Community Risks Please see Exhibit D for a comprehensive analysis of risks.

3 6.0 Proposal Benefits and Costs The structure and content damages are different for each project condition. The first increment of work to be completed will be structure buyouts along portions of the East Branch. These buyouts will remove some of the most at risk properties. Buying out structures is not being proposed as a standalone scenario, but it has been displayed as an increment in the table and graph below. Buying out structures removes potential future damages and shifts the curve to a lower damage total. The levees and buyouts plan is displayed in a gray dashed line in the graph below. The proposed levees should reduce flooding risk up to a 0.01 frequency event (100 year recurrence interval), effectively removing all damages for all lower events. The residual risk for events exceeding a 0.01 frequency occurs when the levee is overtopped. During an overtopping event, the remaining structures would be expected to experience significant damages. The final alternative provides further damage reduction by elevating all remaining structures on the east side of the East Branch. By elevating these structures, they will be placed above the base flood elevation and only experience damages at less frequent events. Table Structure and Content Damages by Plan Recurrence Interval Annual Chance Exceedance Structure and Content Damages Without Project Damages Buyouts Only Levees and Buyouts Levees, Buyouts, and Fill $ - $ - $ - $ $ - $ - $ - $ $ - $ - $ - $ $ 644,600 $ 423,900 $ - $ $ 3,579,100 $ 3,044,700 $ - $ $ 4,487,900 $ 3,874,800 $ - $ $ 5,111,500 $ 4,441,100 $ - $ $ 5,287,800 $ 4,604,600 $ 4,604,600 $ 664, $ 5,761,600 $ 4,962,500 $ 4,962,500 $ 948, $ 8,811,900 $ 7,838,600 $ 7,838,600 $ 4,767,900 Notes: The damages are based on water surface elevations, assessor and HAZUS structure information, and USACE depth-damage functions

4 Structure and Content Damages Figure Structure and Content Damages by Plan Lisle Project Damages Recurrance Interval $9,000,000 $8,000,000 $7,000,000 $6,000,000 $5,000,000 $4,000,000 $3,000,000 $2,000,000 $1,000,000 $- Annual Chance Exceedance Without Project Damages Buyouts Only Levees and Buyouts Levees, Buyouts, and Fill

5 The transportation benefits account for the cost in using the vehicle and as well as the opportunity cost for the additional time required to follow the detour. The ADT estimates were provided by the City of Lisle and KSS Fuels (accessed through Google Earth Pro). The detour distance was estimated by USACE and the additional travel time is based on a driving speed of 20 miles per hour. The opportunity cost is based on the median household income for Lisle. Figure Transportation Benefits Street Average Daily Traffic 1 Transportation Costs Avoided Detour Distance 2 Detour Cost 3 (per mile) Additional Travel Time 2 (hrs) Opportunity Cost 4 (per hour) Total Closure Cost 5 Route 53 20,800 3 $ $ $ 152,835 E Ogden Ave 30,000 2 $ $ $ 146,957 Burlington Ave $ $ $ 24,493 1 AADT counts provided by the City of Lisle and KSS Fuels (accessed through Google Earth Pro) 2 Detour distance and time provided by the City of Lisle 3 Detour cost provided by AAA, based on the sedan average cost per mile 4 Opportunity Cost provided by American Fact Finder and estimated using the median household income Lisle, IL, divided by 2000 labor hours for the year 5 This total closure cost represents a closure for a single day The recreation benefits produced by this project were estimated using a USACE methodology where each activity can receive a dollar value per user day. The unit day value of $3.91 is the lowest possible value for general recreation activities and represents a conservative estimate of the value provided by the proposed bike trail. The 50,000 daily user estimate represents a likely number of visitors based on surrounding trail usage. Figure Recreation Benefits Bike Trail Recreation Benefits Project Condition Unit Day Value 1 User Days 2 Total Value Without Project $ - - $ - Levee and Buyouts $ ,000 $ 195,500 Levee, Buyouts, and Fill $ ,000 $ 195,500 1 Values are based on USACE EGM 15-03, Unit Day Values for Recreation for Fiscal Year 2015: general recreation 2 User Days are estimated using local recreation trail counts

6 The FEMA Environmental Benefits Calculator provides a method for evaluating the change from developed land, to natural areas. The calculator provides a dollar value for ecosystem services provided by natural floodplain areas, which was then annualized over a 50 year period and multiplied by the proposed green area square footage. It is assumed that the green areas will require some time to become fully functional ecosystems, so the full value was not applied until the tenth year following construction. This explains the difference in the maximum value provided by FEMA and the annualized value estimated for this project proposal. Figure Ecosystem Services Benefits Ecosystem Service Benefits provided by the East Branch Resiliency Project Project Area Acres Sq Ft Warrenville Storage West Pond Expansion Dumoulin/River Corridor ,376 Natural Land Use Green Open Space Maximum Value 1 (per sq ft) Annualized Value 2 (per sq ft) Total Average Annual Value $ 2.57 $ 1.91 $ 382, ,052 Aquatic $ - $ - $ ,040 Riparian Areas $ $ 9.13 $ 3,578,900 St. Joe Storage West ,648 Riparian Areas $ $ 9.13 $ 2,306,400 St. Joe Storage East ,512 Riparian Areas $ $ 9.13 $ 2,067,800 South St. Joe ,392 Riparian Areas $ $ 9.13 $ 1,272,500 Ogden to Burlington ,800 Riparian Areas $ $ 9.13 $ 1,988,300 Burlington to RR ,848 Riparian Areas $ $ 9.13 $ 318,100 RR to Short ,004 Riparian Areas $ $ 9.13 $ 2,346,200 South Short ,680 Riparian Areas $ $ 9.13 $ 1,193,000 Total Restoration Acres ,925,352 varies varies varies $15,453,700 1 Values are based on FEMA's Environmental Benefits Calculator (V2) and are annualized at the OMB rate of 7% 2 Annualized over a 50 year period at 7%, with the assumption that the natural areas will be fully functional 10 years after construction

7 In accordance with the HUD Resiliency Competition Criteria, all benefits and costs were annualized at an interest rate of 7%. The average annual benefits, costs, and benefit to cost ratios are displayed in the following tables. Figure Average Annual Benefits Benefit Category Average Annual Benefits Without Project East and West Levee West Levee and East Fill Structures and Contents $ - $ 113,000 $ 149,400 Real Estate Benefits $ - $ 4,023,500 $ 3,295,500 Transportation $ - $ 10,700 $ 10,700 Recreation $ - $ 195,500 $ 195,500 Ecosystem Services $ - $ 15,453,700 $ 15,453,700 All Categories $ - $ 19,796,400 $ 19,104,800 Notes: These benefits have been annualized at a rate of 7% over a period of 50 years Figure Average Annual Costs Benefit Category Average Annual Costs Without Project East and West Levee West Levee and East Fill Total First Cost $ - $ 80,061,800 $ 65,217,100 Total OMRR&R $ - $ 4,003,100 $ 3,260,900 Compounding During Construction 1 $ - $ 12,021,100 $ 9,792,200 Average Annual Cost 2 $ - $ 84,064,900 $ 68,478,000 1 This is an estimate of the time value of the construction expenditures, assuming a 5 year schedule, compounded at 7% 2 These benefits have been annualized at a rate of 7% over a period of 50 years

8 Figure Benefit Cost Ratios Category Benefit to Cost Ratios Without Project East and West Levee West Levee and East Fill Average Annual Benefits $ - $ 19,796,400 $ 19,104,800 Average Annual Costs $ - $ 4,003,100 $ 3,260,900 Average Annual Net Benefits $ - $ 15,793,300 $ 15,843,900 Benefit to Cost Ratio Notes: These benefits and costs have been annualized at a rate of 7% over a period of 50 years 7.0 Project Risks Please see Exhibit E for project risks. 8.0 Implementation Challenges Please see Exhibit E for project feasibility.