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Suggested Citation:"Chapter 5 - Costs." National Academies of Sciences, Engineering, and Medicine. 2019. Benefit–Cost Analyses Guidebook for Airport Stormwater. Washington, DC: The National Academies Press. doi: 10.17226/25617.
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Suggested Citation:"Chapter 5 - Costs." National Academies of Sciences, Engineering, and Medicine. 2019. Benefit–Cost Analyses Guidebook for Airport Stormwater. Washington, DC: The National Academies Press. doi: 10.17226/25617.
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Suggested Citation:"Chapter 5 - Costs." National Academies of Sciences, Engineering, and Medicine. 2019. Benefit–Cost Analyses Guidebook for Airport Stormwater. Washington, DC: The National Academies Press. doi: 10.17226/25617.
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Suggested Citation:"Chapter 5 - Costs." National Academies of Sciences, Engineering, and Medicine. 2019. Benefit–Cost Analyses Guidebook for Airport Stormwater. Washington, DC: The National Academies Press. doi: 10.17226/25617.
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Suggested Citation:"Chapter 5 - Costs." National Academies of Sciences, Engineering, and Medicine. 2019. Benefit–Cost Analyses Guidebook for Airport Stormwater. Washington, DC: The National Academies Press. doi: 10.17226/25617.
×
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Suggested Citation:"Chapter 5 - Costs." National Academies of Sciences, Engineering, and Medicine. 2019. Benefit–Cost Analyses Guidebook for Airport Stormwater. Washington, DC: The National Academies Press. doi: 10.17226/25617.
×
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Page 43
Suggested Citation:"Chapter 5 - Costs." National Academies of Sciences, Engineering, and Medicine. 2019. Benefit–Cost Analyses Guidebook for Airport Stormwater. Washington, DC: The National Academies Press. doi: 10.17226/25617.
×
Page 43
Page 44
Suggested Citation:"Chapter 5 - Costs." National Academies of Sciences, Engineering, and Medicine. 2019. Benefit–Cost Analyses Guidebook for Airport Stormwater. Washington, DC: The National Academies Press. doi: 10.17226/25617.
×
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Suggested Citation:"Chapter 5 - Costs." National Academies of Sciences, Engineering, and Medicine. 2019. Benefit–Cost Analyses Guidebook for Airport Stormwater. Washington, DC: The National Academies Press. doi: 10.17226/25617.
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37 Identification of the relevant costs and estimation of reasonable values for them are crucial to conducting a useful BCA and can also be extremely chal- lenging. Information on costs may help airports that wish to undertake a BCA internally with their own staff and may also help airport staff working with consultants ask informed questions. The available cost information will vary depending on the stage of the project planning and the associated cost estimation that has been done at the time of the BCA. Cost estimates may be more challenging for projects involving newer or innovative approaches such as GSI, and margins of error will mostly likely need to be larger for such projects. The costs covered in this chapter are primarily financial costs, but also discussed are a limited number of environmental and social costs. The sections that follow discuss factors affecting the costs of airport stormwater infrastructure and resources for obtaining or estimating costs; also included is a listing of costs to consider and potential approaches for assigning values (Tables 14 and 15). 5.1 Factors Affecting Costs of Stormwater Infrastructure Projects at Airports Capital costs, O&M costs, and the costs to comply with government regulations all factor into the total costs for stormwater infrastructure projects at airports. A range of factors can influence these costs, including wage rates, operational cost constraints, and environmental compliance costs. Airports also have unique stormwater considerations that affect their project designs. Air- port operations are governed by strict safety and environmental regulations. Cost savings cannot come at the expense of aircraft and passenger safety. The FAA provides guidance on outlining the costs for a BCA (see Appendix B for more details), and supplemental information can be drawn from local airports and state DOTs. Costs for planning, designing, and constructing stormwater infrastructure at airports can be significantly higher than costs for other transportation infrastructure projects. This can be attributed to the heavy live loads that aircraft impart on subsurface stormwater structures, airport operational constraints, the need to consider other airport-specific issues (e.g., wildlife hazards), and increased environmental compliance requirements. Additional factors affecting costs include: • Recordkeeping requirements, • Regional labor rates, • Location (e.g., heavily populated versus rural, coastal versus inland), including differences in local or state commitment to GSI and LIS, C H A P T E R 5 Costs

38 Benefit–Cost Analyses Guidebook for Airport Stormwater • Bidding situation (including how many bidders there are and other developments in the region that may compete for the pool of contractors), • BMP type (costs more difficult to estimate for green infrastructure BMPs than for gray infra- structure, which is more standardized and lends itself more readily to cost estimating), and • Time of year for bidding. A discussion of the following factors affecting costs can be found in Appendix E: aircraft loading, airport operational constraints, wage rates, type of construction, and environmental compliance. 5.2 Resources for Estimating Costs The level of detail required for cost estimates depends on the needs of the analysis and data that are available. Detailed cost analyses for a well-defined project are generally done using contractor support. Bid tabs are a common source of cost data for contractors and could also be a useful source of information for airport staff. Current hourly labor rates may be available from prior construction bids (for con- tractors) or the airport’s finance and human resource departments (for airport personnel). The References and Additional Resources section includes resources on cost estimation methods and values for costs from specific projects or presented as typical or average values. Other common sources of cost data are commercial products such as RSMeans, a construction cost data and software system. For pre- engineered or proprietary structures, engineers may contact vendors and get a range of prices. Other approaches for estimating costs can include direct communi- cation with other organizations, state and local reports with cost elements for stormwater BMPs, and resources made available by the U.S. EPA and other organizations. Airports interested in the feasibility of implementing green infrastructure may be able to identify similar projects through listings and resources such as the International Stormwater BMP Database (discussed in Table 7). Airports interested in pursuing GSI can refer to reports describing its benefits and costs. A variety of approaches and information sources may be helpful for initial rough estimates for project types that the airport has not undertaken before. In identifying and assigning values to costs, all relevant airport staff should be consulted, including staff in environmental compliance, O&M, capital development, engineering, and finance. The input of the O&M staff will be especially critical in estimating life-cycle costs. Also, it is important to remain aware of uncertainties in estimates, taking into consideration the type of information and level of detail. 5.2.1 Contractor Support Consultants and contractors can also support airports in making sure that project designs meet with environmental requirements (federal, state, and local) as well as FAA and other regulations. Detailed cost estimates are generally done using engineering design and construction con- tractors and may include the total cost of ownership. (The total cost of ownership includes the purchase price of an asset plus the costs of its O&M; it may also include environmental or social costs associated with the asset.) Stormwater infrastructure contractors, engineering firms, and Do You Have What You Need? Some airports have expressed interest in guidance on where to locate cost information for initial scoping-level estimates. Guidance on O&M costs: airports have indicated that total cost of ownership can be more difficult to estimate than up-front capital costs.

Costs 39 other consultants used by other airports and large landholders may be relevant sources of information about costs for projects. 5.2.2 Communicating with Other Airports and Other Landholders Airport staff who are interested in stormwater infrastructure designs with which they and their engineers are less familiar may benefit from contacting other airports, port authorities, other transportation facilities (highway administrations), and other large landholders that have installed that type of BMP. This may be especially valuable for learning about challenges encoun- tered during design, construction, and post-construction. Hearing about this practical experi- ence may help in planning the life-cycle costs of a structure, including unexpected O&M costs or other difficulties. This may be especially useful for airports interested in implementing GSI and LID. 5.2.3 Bid Tabulations Bid tabs on previous projects of a similar type and in the same region are a good source of cost information for consultants. Consulting groups may have their own in-house libraries of bid tabs, but municipalities and DOTs make bid tabs publicly available on their websites. These listings are detailed and can help airport staff understand typical costs for activities and materials for infrastructure projects. The data for specific line items are generally aggregated across bids, and average, low, and high values may be provided. In some cases, bids may be listed separately. The items listed can include specific parts, activities that are a part of a larger project, or whole costs for installation. Bid tab data can often be downloaded as PDF or Excel files. Some states have an interface that allows search parameters to be set. The airport’s consulting engineers may be able to provide information from their own libraries of bid tabulations. Table 12 shows state DOT websites where bid tabulations can be found. These illustrate some of the types and formats of data available. Readers are encouraged to visit the DOT websites for their states and, if appropriate, adjoining states. How Do Airports Get Their Estimates? Detailed cost analysis: Dallas/Fort Worth International Airport notes that it typically does detailed cost analyses rather than a formal BCA for stormwater projects, with estimates done by consulting engineers. In-house process: Denver International Airport has its own in-house department that produces initial estimates as part of a formalized internal process for project selection and prioritization; its detailed cost analyses are produced by consultants for those projects that go to the design phase. In-house process: Southwest Florida International Airport compiles initial cost estimates based on experience and information from past projects and discussions with other airports that have done similar projects.

40 Benefit–Cost Analyses Guidebook for Airport Stormwater Organization Resource Description U.S. EPA Green Infrastructure Cost–Benefit Resources Links to examples of BCAs and tools. Focused on communities. CNT Green Values Stormwater Toolbox Evaluate sustainable design opportunities based on research into cost-effectiveness of green infrastructure. U.S. EPA Opti-Tool: EPA Region 1's Stormwater Management Optimization Tool Spreadsheet-based optimization tool used to estimate required pollutant and volume reductions at affordable costs. Focused on New England but can be adapted for use in other regions. U.S. EPA Methodology for Developing Cost Estimates for Opti-Tool Methodology for cost estimation. Links to cost information sources. Focused on New England. Table 13. Examples of resources to evaluate costs. State Website for Bid Data California http://www.dot.ca.gov/hq/esc/oe/awards/ Louisiana http://www.apps.dotd.la.gov/engineering/lettings/WeightedAverages.aspx New York https://www.dot.ny.gov/divisions/engineering/design/dqab/waipr Texas http://www.txdot.gov/business/letting -bids/average-low-bid-unit-prices.html Table 12. Examples of bid tabulations from state DOTs. 5.2.4 Resources Provided by EPA, States, Local Agencies, and Other Organizations Entities such as the U.S. EPA, the CNT, and state agencies have made resources available through websites that can help in assessing benefits and costs of stormwater BMPs, including GSI and LID. States and municipalities have documented BMP costs in downloadable reports. These provide information such as typical BMP installation costs and, in some cases, O&M costs. Because labor and material costs vary nationally, airports should look for such documents in their own or nearby states or in states with labor and other rates generally similar to their own. Google searches or searches of the websites of relevant state agencies can help in identifying other reports with similar information. Table 13 provides examples of resources from the EPA, state and local agencies, and other entities (see the References and Additional Resources section for further information, such as URLs). Although these resources are not specifically targeted to the aviation industry, the information can provide a starting point for airports to estimate BMP costs, especially for those implemented landside, where BMPs may be similar to those used at other large commercial properties.

Costs 41 Multidisciplinary Digital Publishing Institute Performance and Cost Perspective in Selecting BMPs for Linear Projects Evaluates costs and performance effectiveness of BMPs that retain post-construction stormwater on site. Organization Resource Description American Society of Civil Engineers Cost-Estimating Tools for Low- Impact Development Best Management Practices: Challenges, Limitations, and Implications Evaluates tools to estimate capital costs, O&M costs, and life-cycle NPV of vegetative roofs, rainwater catchment systems, and bioretention facilities. U.S. Army Corps Cost-Estimation Tool for Low- Impact Development Stormwater Best Management Practices Describes tools used to estimate BMP costs. NOAA A Guide to Assessing Green Infrastructure Costs and Benefits for Flood Reduction Provides guidance on recording the costs of flooding, projecting increased flooding and associated costs, and calculating the long- term benefits and costs of implementing green infrastructure. WERF Economic Evaluations of Stormwater BMPs Provides information on evaluating stormwater BMPs for cost- effectiveness and gained economic benefits. City of Rockville Department of Public Works Standard Prices for Cost Estimating Includes estimated unit costs for public works projects (e.g., storm drain structures). Water Research Foundation BMP and LID Whole Life Cost Models Tool to estimate whole-life costs for stormwater BMPs. Delaware Department of Natural Resources and Environmental Control Appendix E: BMP Cost Calculations (Delaware Department of Natural Resources and Environmental Control, n.d.) Evaluates costs of urban and agricultural BMPs to reduce nutrients in stormwater. U.S. EPA National Stormwater Calculator Tool that analyzes costs of various green infrastructure and LID practices. Maryland Department of the Environment Stormwater BMP Unit Cost Estimates Excel workbook developed by the Maryland Department of the Environment. Contains tabs to help with stormwater BMP cost estimation. Minnesota Pollution Control Agency Best Management Practices Construction Costs, Maintenance Costs, and Land Requirements Summarizes costs for eight structural LID BMPs and estimates life-cycle costs. Minnesota Pollution Control Agency Minnesota Stormwater Manual Comprehensive manual in Wiki format, with an extensive list of BMPs with tables of cost and benefit considerations, including cost estimate worksheets. Table 13. (Continued).

42 Benefit–Cost Analyses Guidebook for Airport Stormwater 5.3 Financial, Environmental, and Social Costs and Approaches to Assigning Value To the extent possible, the airport must assign values to anticipated costs so that they can be incorporated into the BCA. Assigning monetary values for costs may be more straight forward than for benefits because costs are more typically documented and tracked over time. Even costs that are not explicitly tracked by the airport often can be estimated using other data available, such as wage rates and staff time requirements. There may be additional costs or additional approaches to estimating costs that airports may develop based on their own (and potentially their consultants’) experience and the needs of the airport. Additional information and resources for identifying and estimating costs can be found in the References and Additional Resources section. Tables 14 and 15 provide example financial, environmental, and social costs that may apply to a stormwater infrastructure project along with suggested approaches for assigning values to those benefits. 5.4 Bayside Airport’s Costs BAY’s team researched costs using a process similar to that used for the benefits. The team relied more heavily on engineers’ estimates and bid tabs to develop comprehensive life-cycle costs for each option. BAY’s team began by analyzing capital and O&M costs associated with past projects. The airport had previously built stormwater infrastructure similar to that planned in Option 1, and the team collected the most relevant past costs, adjusting them for inflation to be in 2018 dollars. BAY did not have any past projects resembling the subsurface detention with system vaults and reuse (Options 2 and 3) or the bioretention cells (Option 3). To better understand the potential costs for these systems, the team used cost estimates provided by OSD for similar stormwater projects developed on the airport’s property. BAY’s team adapted OSD’s up-front capital costs and maintenance costs for the first few years and scaled them down to meet the parameters of BAY’s projects, which addressed a smaller runoff area. (When BAY is further along in the planning process, it can improve its cost estimates by hiring engineers to develop a bid for the specific project.) Table 16 summarizes the final values identified by the team through its research efforts. As with the analysis of long-term benefits, the team ensured that the annual or periodic costs selected for the analysis represented reasonable average values per year (or per specified period). The team was able to approximate monetary values for all costs and will adjust those estimates, if needed, as the planning process proceeds. Because of the uncertainty surrounding these cost estimates, BAY’s team flagged these costs for further evaluation in the sensitivity analysis (to be conducted at the end of the analysis).

Costs 43 Capital costs Permitting costs Suggested approaches: estimated number of hours of consultant time × hourly rate, total project cost × percentage. Suggested approaches: estimated number of hours for airport staff time (approximately 20 to 25 hours) × staff labor rate, percentage of total project costs (e.g., 2%). Capital costs Construction phase (including material and equipment) Suggested approaches: preliminary cost estimate, general estimates from bid tabs, overall costs for similar projects, vendor quotes, communication with other airports, or literature. Capital costs Other staff or consultant time Other anticipated staffing needs, including time for putting financing together. Suggested approaches: staff time × average rate or other estimate of costs of staff time. Category Element Example Approaches to Assigning Value Capital costs Engineering/design Estimate of design costs. Could be based on design costs for other projects of similar total cost or complexity, or expected percentage of total project cost (e.g., 8%). Capital costs Financing – costs of borrowing Suggested approaches: use interest rate and length of loan if financed. If project is self-financed, use airport’s average cost of capital. O&M Labor Anticipated maintenance types (e.g., mowing, plant maintenance, trash removal). Suggested approaches: estimated annual and total FTE × average staff total compensation × anticipated number of years in life span of BMP. For BMP designs with which the airport is unfamiliar, use a general estimate from other sources (e.g., reports, discussions, BMP guides). O&M Materials and equipment after construction Examples: sand filters, mulch, plant replacements needed for the useful life of the BMP. Suggested approaches: estimates from vendors, bid tabs, or other sources (e.g., reports, discussions, BMP guidance). Estimated frequency of need × anticipated life span of BMP. O&M Disposal Costs for disposal of trash, filter media, vegetation, etc. Suggested approaches: costs × estimated frequency of need × anticipated life span of BMP. O&M Wildlife deterrents Estimated one-time and annual costs for wildlife deterrents, if needed. Suggested approaches: annual costs × years of useful life of the BMP. Table 14. Example financial/economic costs and suggested approaches to assigning value. (continued on next page)

44 Benefit–Cost Analyses Guidebook for Airport Stormwater Category Element Example Approaches to Assigning Value Social Inconvenience of service disruption to customers Customer costs associated with interruptions in airport operations while project is under construction or undergoing major maintenance. Suggested approaches: reduction in enplanements due to construction, hours lost by customers for delayed or cancelled flights, and hourly value of customer time. Environmental Ecological impacts Ecological effects associated with the project’s materials, wastes, or energy use during construction, operation, maintenance, or decommissioning. Suggested approaches: typical costs for cleanup of waste materials that could reach receiving waters or ecologically sensitive areas. Environmental Groundwater impacts Potential for migration of pollutants to groundwater. Suggested approaches: risk represented as known levels of contamination in soil that could be mobilized by percolating stormwater, risk represented by soil properties and the likelihood that the soil will retain pollutants in the runoff, presence or absence of hot spots of spills or other pollution near the BMP. Environmental Hazardous waste Suggested approaches: percent of facility or disposable elements that require handling of hazardous materials, disposal, and tracking; could be counted under financial costs instead. Table 15. Example environmental and social costs and suggested approaches to assign value. Table 14. (Continued). Category Element Example Approaches to Assigning Value Other costs Deconstruction Estimated cost of removal in today’s dollars. Note: This is often not planned for and is a hidden cost that is incurred years down the road. Suggested approaches: estimate cost of deconstruction as a percentage of the cost of the initial investment. End-of-life reusability Hazardous materials handling and disposal Hazardous waste handling and disposal of materials at the end of the project (e.g., filter sand or soil media contaminated with fuels or metals) Suggested approaches: “yes” or “no.” Dollar value for disposal or tonnage of reuse.

Costs 45 Cost Value Source Incurs up-front costs for planning, permitting, and construction Option 1: $2.4 million Option 2: $3.7 million Option 3: $3.6 million Source: costs on past projects at BAY, scaled costs from OSD’s projects, and online stormwater BMP cost estimation tool. Notes: BAY’s team used past BAY projects to estimate the cost of the dry detention basin and adjusted the costs to 2018 dollars to account for inflation. For the bioretention cells in Option 3, the team referenced an online tool that provides a range of costs for common stormwater BMPs (represented as cost per sq ft of catchment area). The team used the middle value for commercial construction and multiplied it by the size of the project’s catchment area. For the subsurface detention system with and without water reuse, the team used costs for past projects at OSD and scaled the values to be representative of the size of BAY’s catchment area. Because of the uncertainty surrounding this estimate, BAY’s team flagged this cost for further evaluation in the sensitivity analysis (to be conducted at the end of the analysis). Incurs long-term O&M costs Option 1: $14,300 annually Option 2: $191,900 annually Option 3: 197,600 annually Source: costs on past projects at BAY, scaled costs from OSD’s projects, and online stormwater BMP cost estimation tool. Notes: BAY’s team used the same approach to estimate annual O&M costs as described for up-front costs. Incurs end-of-life decommissioning costs Option 1: $121,000 after 50 years Option 2: $184,500 after 50 years Option 3: $181,400 after 50 years Source: costs on past projects at BAY, scaled costs from OSD’s projects, and online stormwater BMP cost estimation tool . Notes: Based on past experience with infrastructure projects, BAY will likely have costs at the end of the infrastructure’s life to decommission it. This could include salvaging materials, plugging stormwater holes, or filling detention basins. BAY’s team estimates that approximately 5% of the construction cost will be needed to decommission the infrastructure at the end of its useful life. Incurs cost of education campaign Option 1: $0 Option 2: $90,000 up front Option 3: $90,000 up front Source: costs on past education campaigns at BAY. Notes: BAY has conducted numerous education and outreach efforts on past projects at the airport. BAY’s team used past costs from one of these efforts and adjusted the costs to 2018 dollars to account for inflation. Table 16. Final values for costs.

Next: Chapter 6 - Compare Benefits and Costs »
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Many airports undertake stormwater projects to accommodate facility expansion, address obsolescence, and respond to evolving regulatory requirements. Often, stormwater infrastructure is installed or upgraded on a project-by-project and piecemeal basis, resulting in mismatches of sizes, material types, ages, and conditions.

When airports are considering expanding or improving their stormwater facilities, the immediate need for stormwater infrastructure modification may not be clear, and a benefit–cost analysis (BCA) is needed.

The TRB Airport Cooperative Research Program's ACRP Research Report 208: Benefit–Cost Analyses Guidebook for Airport Stormwater provides guidance on using BCAs to identify, evaluate, and select airport stormwater management projects. The guidance focuses on a triple bottom line approach that considers an airport’s finances and environmental and societal impacts. The guidance will be particularly helpful for small airports that may not have BCA expertise or experience with innovative stormwater projects.

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