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Benefit–Cost Analyses Guidebook for Airport Stormwater (2019)

Chapter: Chapter 2 - Plan the Analysis and Identify Data Needs

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Suggested Citation:"Chapter 2 - Plan the Analysis and Identify Data Needs." 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 2 - Plan the Analysis and Identify Data Needs." 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 2 - Plan the Analysis and Identify Data Needs." 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 2 - Plan the Analysis and Identify Data Needs." 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 2 - Plan the Analysis and Identify Data Needs." 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 13
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Suggested Citation:"Chapter 2 - Plan the Analysis and Identify Data Needs." 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 2 - Plan the Analysis and Identify Data Needs." 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 2 - Plan the Analysis and Identify Data Needs." 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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9 Airport staff should begin any BCA with initial planning activities and an assessment of data needs. Thinking through several decisions early in the pro- cess will help the airport identify and collect the data it needs and position the airport for a smooth BCA. As previously mentioned, a BCA can be conducted at a high level early in the planning process or when limited resources are available. It can be more extensive when an airport has the necessary resources and is far enough along in the planning process to have the information needed to support a detailed analysis. Regardless of the approach, this chapter identifies planning and data consider- ations that will be essential to the analysis. Additional resources and tools airports can use when planning their BCA can be found in Appendix F. 2.1 Framing the Analysis To frame and prepare for a BCA, the airport should: • Clearly define the infrastructure alternatives. The airport staff should clearly identify and define the infrastructure alternatives that will be considered in the analysis. The project alter- natives and their associated benefits and costs should fit within the organization’s strategic plans and policies (e.g., energy, expansion plans). The level of detail for each alternative will depend on the airport’s stage of planning and the available data and resources. At an early stage of planning, alternatives may be broadly defined, and costs likely will be approximate. At a minimum, the airport should define the scale and main components of each alternative (e.g., type of detention basin, water treatment, capture, storage, and reuse) and be certain that they can be designed and constructed to meet regulatory requirements and the airport’s storm- water system performance needs. At this stage, an airport may wish to include alternative stormwater BMPs that are considered innovative or that are outside of its experience, such as green stormwater infrastructure (GSI) BMPs. Airports may also have initial consultations with researchers, engineers, or local or state per- mitting authorities to determine if design alterations may be possible to make certain types of BMPs better suited to airports. Once the airport has identified two or three alternatives among which to make a final decision, these alternatives must be defined in more detail. • Gather input from staff with complementary skills. Throughout this process, the airport should include project team members with complementary skills to help analyze project alternatives, antici- pate project outcomes, identify appropriate metrics, and review and evaluate the results of the analysis. These team members should cover the array of specialties that would be affected by the proposed C H A P T E R 2 Plan the Analysis and Identify Data Needs Looking Outside for Expert Input Some airports, particularly small airports, may not have in-house expertise or skills needed to fully analyze the project alternatives. In these cases, airports can seek input and support from neighboring airports or outside experts.

10 Benefit–Cost Analyses Guidebook for Airport Stormwater project(s). For example, a stormwater project may require staff specialties like sustainability, environmental quality, compliance, operations and maintenance (O&M), resource manage- ment, finance, and facilities management. In addition, communications personnel may detect points of value that only the customers or local community experience. • Identify stakeholders. The airport staff must identify the stakeholders that will be responsible for approving the final project selection and consider their priorities throughout the analysis. These stakeholders will most likely include the airport staff, including the engineers, planners, and, typically, the airport manager. The airport’s governing body also likely will need to approve final selection. Additionally, FAA approval may be required. Some members of the airport’s BCA team may also be integral to the airport’s project approval process. The airport staff will also need to identify those who will be affected by the project and recognize them as potential stakeholders. A holistic BCA that addresses the TBL will benefit from stakeholder perspectives and insight on potential social, economic, and environmental outcomes of the project alterna- tives. Furthermore, stakeholders can affect the progress of the project through their support or opposition. Anticipating the priorities of these stakeholders at the beginning of the BCA will help the airport incorporate relevant benefits and costs into the analysis and potentially gain support of stakeholders when the analysis is complete. Potential stakeholders for stormwater infrastructure projects may include airport staff, passengers, neighboring communities, local environmental groups, and businesses that rely on the quality of receiving water. • Confirm the term of the analysis. The term of the analysis should be carefully selected to account for the useful life of the project and any regulatory or economic changes that are anticipated. For example, if new regulations are expected to be implemented within 5 years and the project term is 25 years, the analysis should address these two separate time periods to account for the regulation’s potential effect on benefits and costs. The first 5 years would reflect costs associated with current regulations, and the subsequent 20 years would reflect any cost differential associated with the new regulations. Costs for a stormwater infrastructure project are often incurred up front, while the benefits accrue over the life of the infrastructure. As a result, the term of the project could affect the final outcome of the analysis. • Conduct comprehensive analysis of project outcomes. The airport staff should work with the airport’s design team and stakeholders to identify the potential project outcomes of each potential alternative. This exercise should take into account the potential impact of the project on the TBL. This process may require development of focus areas to prompt thinking, particularly for the environmental and social accounts, which may be outside of the airport’s typical scope of planning. The list of potential outcomes can be augmented later in the process when the airport staff dives deeper into the research on benefits and costs. 2.2 Data Needs and Considerations A comprehensive analysis of benefits and costs requires the best information available to the airport at the time for all relevant benefits and costs. In general, the main benefit of an invest- ment project is increased revenue. For example, a new runway increases capacity, which in turn generates additional revenue for an airport. But many projects—especially well-designed stormwater projects—may also produce other benefits over the useful life of the project, such as improved regulatory compliance and improved ability of the airport to operate in inclement weather. These benefits may not generate revenue but are still important to keep the airport functioning. Considerations for Small Airports Small airports may need to rely on outside information to anticipate project outcomes. For example, project outcomes can be developed by contacting comparably sized airports that have undertaken similar projects. The local FAA Airport District Office or local state aviation organization may also be able to help.

Plan the Analysis and Identify Data Needs 11 Costs include the cost of the initial investment, as well as necessary O&M expenses and decommissioning costs. The initial investment will typically include expenses like labor, materials, consultant costs, and the cost of the equipment. O&M costs may include additional labor and replacement materials. Factors affecting the costs of stormwater infrastructure projects at air- ports are discussed in Chapter 5 and Appendix F. Ideally, the benefits and costs of a project should be measured in dollars. This may be easier to do for costs, which often have a clear price. The sections that follow discuss some general data need considerations. More detailed discus- sions of benefits and costs are presented in Chapters 4 and 5. 2.2.1 Triple Bottom Line Environmental and social benefits and costs can be brought into the analysis to account for the full benefits and costs of a project; these are further discussed in Chapters 3, 4, and 5. As the project team identifies potential outcomes of each project option, they can begin to organize them into the most appropriate TBL category. Details on how to conduct an analysis using TBL are provided later, but anticipating data needs from the TBL perspective at this stage of the analysis can be helpful for understanding the big-picture analysis and the data collection process. 2.2.2 Quantitative Versus Qualitative Values The most straightforward way to incorporate benefits and costs into a BCA is to measure their monetary value. In some cases, benefits and costs may not easily be expressed as a dollar value but can be quantified by other measures (e.g., hydrologic performance, pollutant removal rates, and land area). If there are no adequate data to quantitatively evaluate a benefit or cost, a qualitative measure such as a “yes” or “no” or a ranking on a scale may be most appropriate. Some measures may be able to be assigned a quantitative value at one airport but will need to be evaluated qualitatively at a different airport due to differences in available information and the level of detail that is needed or feasible for the BCA. Chapter 4 provides suggested approaches to assign value to benefits, with examples of both quantitative and qualitative options. 2.2.3 Types of Data Sources Before beginning a comprehensive data search, the project team should research potential data sources for each alternative. Data on benefits and costs of airport stormwater infrastruc- ture projects can come from many sources. In some cases, detailed estimates of the costs of a stormwater project and associated benefits may be available from similar, recent projects done by the airport’s consultants, other airports in the region, or at other similar sized airports in the country. In other cases, estimates may require assumptions about a project’s design and perfor- mance, especially if an innovative design or new product without available cost and performance information is being used. The further along an airport is in developing project alternatives, the more likely it is that it will have better cost estimates. The BCA can be more detailed and refined at these later stages. Consulting engineers are a primary source of detailed cost information (as described in Chap- ter 5). Some airports have in-house estimating capabilities to support planning. Other potential sources of information about project costs include state departments of transportation (DOTs), bid tabulations (bid tabs) (often available from DOTs), and contractor reports. Information on benefits can come from diverse sources such as permit requirements and compliance history, anticipated BMP performance, airport sustainability goals, and airport interest in educational efforts and community interactions. Much of the available information

12 Benefit–Cost Analyses Guidebook for Airport Stormwater on the benefits, costs, performance, design, and other aspects of stormwater BMPs, including GSI, is not tailored to airports. Such information may be applicable nonetheless, especially for landside projects. Airport staff should use this information while also considering issues that are unique to airport settings. ACRP Report 174: Green Stormwater Infrastructure Strategies (Jolley et al., 2017) provides airport-relevant information on several GSI BMPs. 2.2.4 Data Summary Matrix The type and quality of data needed to support a BCA will depend on the objectives of the analysis. For example, if an airport needs to measure the NPV of alternative stormwater projects, it will need reasonable estimates of the monetary value of the project’s benefits and costs to the airport, the environment, and society. On the other hand, if it needs to rank potential projects based on several criteria, qualitative measures of the impact of the project and its costs may suf- fice. Of course, the type of analysis airports can conduct will depend on the quality and type of data that are available. Airports may need to tailor their analysis to the data available. Table 1 provides examples of the types of analyses airports can use to compare projects, depending on the resources they have and the quality of the available data. The table shows four situations. In the first, the airport has few resources (staff hours and budget) and poor-quality data. The quality of the data may be poor because they are incomplete, lacking in detail, or of uncertain accuracy. In the second situation, the airport has access to rich, detailed, high-quality data but continues to have few resources to evaluate the data. In the third situation, the airport has many resources, but the data available are poor. In the final situation, the airport has many resources available to it and rich data to work with. These four cases represent points along a continuum. They demonstrate the types of choices airports will need to make when they plan their analyses. After conducting the resource and data assessments, the airport can determine whether it is equipped to conduct a basic or rigorous BCA. An airport with few resources and poor data is equipped only for a basic analysis that provides rough estimates of the potential benefits and Resources Available Data Quality Analytical Approaches to Consider Few Poor • Checklists of benefits and costs • Qualitative ranking of outcomes Rich • Checklists of benefits and costs • Qualitative ranking of outcomes • Back-of-the-envelope NPV and B/Cs using existing estimates of benefits and costs • Qualitative assessments of nonmonetary benefits and costs Many Poor • Checklists of benefits and costs • Development of preliminary estimates of monetary benefits and costs • Development of qualitative descriptions of other benefits and costs associated with each project • Qualitative ranking of outcomes Rich • Checklists of benefits and costs • Development of detailed estimates of monetary benefits and costs • Development of qualitative descriptions of other benefits and costs • Development of monetary measures of other benefits and costs, based on the literature or results of other projects • Qualitative ranking of outcomes • Estimation of NPV and/or B/C • Estimation of payback period and internal rates of return based on estimated timeline Table 1. BCA methods and resource and data requirements.

Plan the Analysis and Identify Data Needs 13 costs of a project. This level of analysis can be informative to supplement decision making, but the airport must identify and clearly communicate its limitations (e.g., uncertainty of project costs, lack of monetized benefits, or uncertainty of qualitative outcomes). An airport with few resources and rich data may not have the resources to conduct a rigorous analysis in-house or hire outside consultants, but it may be able to conduct an analysis of moderate rigor by using readily available tools and guidance (such as this guidebook). An airport with many resources and poor data could choose to conduct a basic BCA based on preliminary project data, or it could invest time and funding into development of better data (e.g., hiring consultants to monetize benefits and costs, developing more precise cost estimates). Once an airport has many resources and rich data, it can conduct a rigorous analysis. Consider, for example, a small airport that may have few resources available to conduct a detailed BCA. It may lack data on the performance of stormwater BMPs or their potential ben- efits and costs, and it may not have the staff or money needed to complete the analysis. While this airport may not be able to conduct a full BCA, it can identify the type of costs involved in developing alternative stormwater projects (design, installation, O&M) and the potential impact of each alternative (e.g., the amount of water they can remove, how the project would fit into sustainability plans). It may be able to rank the projects based on this initial assessment of ben- efits and costs. The results of this analysis may indicate that one of the stormwater management approaches is clearly preferred, or they may indicate where additional resources are needed to further evaluate the potential projects. On the other end of the spectrum, a large airport with the staff and resources needed to conduct an analysis and high-quality data to sup- port it can develop a full-scale BCA of a project’s impact on the TBL. The airport may have data from prior projects or can develop detailed estimates of the costs and benefits of each project. It also can develop qualitative assessments of the nonmonetary benefits and costs of the projects and include them in its analyses. Table 2 indicates the types of benefits associated with storm water BMPs. The table includes two conventional and several GSI BMP types. The benefits associated with each BMP (and their magnitudes) will depend on the specific characteristics of each site, including soil, weather, and other characteristics, as well as the specifics of BMP design choices. Some BMPs may or may not infiltrate well depending on soil proper- ties; they may need to be designed with underdrains if soil permeability is low. This affects which benefits will apply (or the degree to which they will apply) at a given airport. These factors could affect the extent to which each BMP reduces total runoff. If the medium in a BMP (e.g., sand filter) is modified to enhance pollutant removal, that will improve pollutant removal benefits. Each BMP will involve design, construction, and O&M costs. The costs will depend on local conditions and the specific design of the BMP. Factors affecting the cost of stormwater BMPs are described in Appendix E. 2.3 Bayside Airport’s Planning BAY assembled an analysis team that included managers in the sustainability, operations, facilities management, finance, and compliance sectors of the airport. The sustainability man- ager was identified as the team lead to spearhead the analysis. This team held a series of planning Considerations for Small Airports Small airports can take advantage of existing data sources to compare potential projects, conducting the analysis using best estimates of benefits and costs. This basic analysis may identify feasible projects and eliminate others that cannot be implemented. Of course, larger airports may face these resource constraints as well. Throughout the guidebook, issues are highlighted that can affect both small and large airports that lack the resources needed to conduct the analysis.

14 Benefit–Cost Analyses Guidebook for Airport Stormwater meetings to develop options for addressing stormwater on the new parking lot and terminal. The project team identified important stakeholders as the surrounding community, passengers, and the airport’s executive board. Discussions in these meetings highlighted important consid- erations that the airport wanted to address: • The airport must comply with water quality requirements defined in the airport’s NPDES permit or face periodic fines. • Bayside City has begun to encourage the use of LID. • The airport staff are aware that contaminated runoff from the airport could harm its resi- dential neighbors and the beach recreation area. The local community has expressed growing concern over pollution in the bay and has recently elevated complaints against the airport regarding the quality of the airport’s current runoff into the bay. • The airport and larger region have identified the effects of climate change as a problem. Drought vulnerability, sea level rise, and storm frequency and intensity are issues that have been growing concerns in the region. • The airport staff wants to consider stormwater options that would meet goals defined in the airport’s water stewardship and sustainability plan. Stormwater BMP Type Ru no ff Vo lu m e Re du cti on Pe ak F lo w W at er Q ua lit y Lo w W ild lif e Ri sk Fr ee d Su rf ac e Sp ac e La rg e Ca pa ci ty Ae st he tic s Su st ai na bi lit y Ed uc ati on G ro un dw at er Re ch ar ge O th er E nv iro n an d So ci al En er gy S av in gs Im pr ov ed O & M W at er R eu se Dry detention basins a Underground detention (vaults and piping) d a, c Bioretention cells, rain gardens b Green roofs a Harvesting and reuse g, c Infiltration trenches, infiltration basins b f Porous pavement d b, c Sand filters d a, b, e f Filter strips d a, b, d Bioswales b Constructed wetlands b a. Sediment and sediment-associated pollutants b. Sediment and dissolved pollutants c. Pretreatment needed d. If BMP is designed to infiltrate (e.g., permeable soils) e. With amended media f. If BMP is installed underground g. Avoids pollutant discharge by harvesting Table 2. Benefits associated with stormwater BMP types.

Plan the Analysis and Identify Data Needs 15 To manage runoff from the new impervious surfaces, BAY has developed the following storm- water management options: Option 1 • Parking lot: A new conventional dry detention basin (approximately 0.3 acres) to capture runoff from the parking area expansion (10 acres of new impervious surface). Runoff will be discharged from the detention basin to the bay. • Terminal: A subsurface detention system to capture runoff from the new terminal area (15 acres). Captured runoff will be discharged to the bay. A forebay chamber sold by the infrastructure vendor will allow particulates to settle before discharge. Option 2 • Parking lot: A new detention basin to capture runoff from the parking area expansion (10 acres of new impervious surface). Runoff will be discharged from the detention basin to the bay (same as Option 1). • Terminal: A subsurface detention system to capture runoff from the new terminal expan- sion (15 acres). Captured runoff will be treated and used for non-potable reuse on airport property (e.g., irrigation, flushing toilets, cooling systems). The underground system will be equipped with a treatment system with (1) an oil–water separator located at the beginning of the detention system to improve quality, and (2) a biofiltration system via engineered soil vaults. Option 3 • Parking lot: Five bioretention cells around and in the parking area in lieu of the detention basin. The cells will be designed primarily to infiltrate, but during large storm events, overflow will discharge to the existing storm sewer system and to the bay. • Terminal: A subsurface detention system with treatment and water reuse (same as Option 2). BAY’s team estimated that the useful life of the infrastructure would be 50 years. At that point, the infrastructure would require major rehabilitation or decommissioning. After defining the three stormwater infrastructure options, the planning team identified potential outcomes of each scenario to help guide the data collection process. This process involved input from the entire planning team. The team worked with the airport’s commu- nications director to convene a focus group consisting of key stakeholders in the area to fully understand how each option would affect the stakeholders and to document their primary con- cerns. BAY also identified which bottom line (financial, environmental, or social) each outcome would affect (see Table 3). Some outcomes could be counted under more than one group. BAY will make a final decision about where each will fall in the next stage of the BCA. BAY will also evaluate the magnitude of each of these outcomes later in the analysis when it develops benefits and costs. BAY decided to conduct the analysis in real 2018 dollars, starting in 2021 and going through 2070. The airport staff identified preliminary data sources to help define outcomes and estimate monetary values, including: • Bid tabs from past stormwater projects at the airport, • Construction costs and possibly benefits from a larger airport on the eastern seaboard that developed a water capture and reuse stormwater system,

16 Benefit–Cost Analyses Guidebook for Airport Stormwater • Data on regional beach use from a local university’s environmental department, • Data on beach repairs and costs from Bayside City Department of Parks and Recreation, • A publicly available online tool that produces cost ranges for various stormwater BMPs (residential and commercial), and • Historical meteorological data risks of extreme weather from the National Oceanic and Atmospheric Administration’s (NOAA’s) National Centers for Environmental Information. Outcome Option 1 Option 2 Option 3 Potential TBL Incurs up-front costs for planning, permitting, and construction Financial Incurs end-of-life decommissioning cost Financial Incurs cost to implement education campaign Financial Achieves permit compliance and avoids fines Financial, social, environmental Avoids standing water 48 hours following rain Financial Improves water quality in bay (above permit compliance) Environmental, social Meets airport sustainability goals Environmental Supports city’s focus on use of LID Financial, social, environmental Frees up land surface for other uses Financial Keeps O&M costs low Financial Avoids cost of expanding stormwater conveyance infrastructure Financial Expedites permit process of project (resulting from good will) Financial Improves community relations Social Reduces costs associated with annual stormwater monitoring program Financial Improves conditions on the beach and bay for recreation Social Reduces costs associated with beach erosion through peak-flow attenuation Social Improves aesthetic of airport grounds Social Improves resilience against effects of climate change (i.e., drought, storm patterns, sea level rise) Financial, social, environmental Improves education about water sustainability issues Social Advances regional permitting procedures for green infrastructure Social Uses native vegetation Environmental Table 3. Outcomes and potential TBL (financial, environmental, social) of each project option.

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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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