Watershed Approach to Mitigating Hydrologic Impacts of Transportation Projects: Conduct of Research Report (2022)

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66 Chapter 5. Identification and Evaluation of Co-Benefits This chapter provides a framework for considering co-benefits, as well as costs, of the out-of-kind mitigation techniques introduced in Chapter 2. The primary intended benefit of a stormwater mitigation technique is to compensate for adverse effects of a transportation project on hydrologic metrics. The co- benefits are the “ecosystem services” provided by these mitigation techniques that are in addition to the primary, intended benefit.5 From an economics perspective, ecosystem services describe how ecosystems contribute to human well-being. Ecosystem services are distinct from ecological functions and processes in that they are defined in terms of their value to people. For example, whereas nutrient filtration is an ecological process provided by wetlands, an associated ecosystem service benefiting people may be health benefits associated with improved drinking water quality. Other examples of ecosystem services include climate stabilization, improved wildlife-related recreational opportunities, and aesthetic improvements. Assessing co-benefits can be instrumental in helping State DOTs leverage funding opportunities from external partners/stakeholders, communicate the benefits of a mitigation alternative to the public, decide which of a potential range of projects is most desirable, and/or provide justification for implementing a mitigation technique in place of a more traditional in-kind mitigation technique. For example, where a DOT leverages cost-share partnerships with conservation organizations or local governments and community groups, the objectives of these partners may include consideration of co-benefits, such as creating open space or recreational opportunities and supporting biodiversity. These types of benefits may additionally be compelling to community members. Evaluating co-benefits of out-of-kind mitigation techniques may also help DOT comply with other requirements associated with transportation projects. For example, requirements to consider effects of a transportation project on endangered species (under the Endangered Species Act) or environmental justice (under Executive Order 12898) may influence decision-making regarding the most cost-effective mitigation technique that achieves the hydrological objectives of the mitigation but also benefits listed species and/or low-income or minority populations. Finally, consideration of the co-benefits of mitigation alternatives provides a more complete accounting of the benefits provided by a given mitigation to weigh against mitigation costs. One important finding from the literature review was that much of the literature on costs and benefits of LID and GI relies on case studies (see, for example, EcoNorthwest 2007 and EPA 2013), in part, because of the highly site-specific nature of both the ecosystem service benefits and costs of a given mitigation application. The sections that follow describe a screening process to compare mitigation options by identifying the potential co-benefits associated with a mitigation application and the relative magnitude of those benefits based on the application context (e.g., site-specific environmental and socioeconomic factors that influence the likely ecosystem service co-benefits). This chapter 5The targeted hydrological objectives of the mitigation application are defined as part of step 2 of the decision framework. These targeted objectives, such as mitigating flood risk, are not considered “co-benefits” in the context of this report because co-benefits are defined as additional benefits above and beyond the targeted hydrological objectives. Ecosystem service co-benefits: The benefits people gain from the out-of-kind mitigation techniques beyond the primary, intended hydrologic benefits.

67 additionally discusses well-accepted methods for conducting a more detailed economic analysis when a more precise accounting of co-benefits is needed (e.g., when project partners require it, or monetization of co-benefits is required for a given mitigation alternative to move forward). Specifically, Section 5.1 discusses best practices for identifying co-benefits. Section 5.2 presents a screening stage approach while Section 5.3 discusses the use of more detailed approaches to valuing co-benefits. 5.1. Linkage of Co-Benefits and Mitigation Techniques While the specific suite and value of the co-benefits associated with any given mitigation technique are site-specific, this section identifies the potential categories of co-benefits that may result from a given mitigation technique. Generally, valuing ecosystem services requires linking two types of analyses: ecological production functions, which model the extent to which a mitigation technique generates environmental changes (e.g., in water, air, and habitat quality); and economic valuation methods, which quantify how people benefit from these environmental changes (e.g., health improvements and recreational opportunities). The Federal Resource Management and Ecosystem Services Guidebook (FRMES) provides guidance related to the valuation of ecosystem services in a public decision-making setting and reflects some of the latest thinking regarding ecosystem services valuation (NESP 2016). To appropriately identify and evaluate co-benefits, this framework adopts some of the key recommendations of the FRMES guidance: • Employ causal chains in the identification of ecosystem services. A causal chain tracks the connections between a given landscape-based project, the specific environmental changes that result from project implementation, and then the specific ecosystem services that benefit people. Mapping these causal chains to establish conceptual models of project co-benefits can also help to communicate the pathways through which projects result in a suite of benefits that people receive (NESP 2020). • Evaluate benefits relative to a baseline. To appropriately capture the value of an ecosystem service at a site-specific level, it must be defined relative to a baseline—that is, the level of benefits provided by the site absent implementation of the landscape project. Ecosystem service co-benefits should be evaluated relative to the baseline condition of the project location, prior to or in the absence of the stormwater mitigation implementation. That is, the co-benefits of the mitigation are determined relative to “the world without” this particular mitigation, which may include status quo conditions. • Assess key ecosystem services separately first at a screening level, and potentially with more detailed modeling and analysis, if needed. People benefit from environmental changes in a variety of ways; accordingly, there is not a single valuation approach that encompasses all ecosystem services, but rather different methods are needed to value different types of ecosystem services. At a screening level, it is often possible to evaluate site-specific factors as indicators of the potential magnitude of a co-benefit (e.g., change in stream length available for recreational fishing or the population benefiting from drinking water quality improvements) as opposed to completing a full modeling exercise to quantify the monetary value of the ecosystem service. The FRMES guidebook refers to these metrics as “benefit-relevant indicators,” or BRIs. When available information from the screening analysis is insufficient for decision-making, DOTs may apply existing

68 models to more explicitly evaluate the magnitude of given co-benefits (Section 5.3 describes existing methods and models available to DOTs for this purpose). Figure 5.1 presents examples of environmental changes and types of ecosystem services that may result from out-of-kind mitigation techniques. Table 5.1 defines these example environmental changes while Table 5.2 defines the ecosystem service co-benefits that may stem from such environmental changes. These lists are not intended as a comprehensive accounting of all mitigation co-benefits, but instead to clarify these concepts. In many cases, the general categories of ecosystem service co-benefits are similar across mitigation alternatives (e.g., recreational and health benefits). This similarity is to be expected as all mitigation alternatives have the same primary objective – compensating for hydrologic impacts. However, the specific nature and magnitude of these co-benefits may vary significantly across mitigation alternatives (e.g., increased forest hiking opportunities versus increased fish populations for recreational fishing). Figure 5.1. Examples of mitigation techniques, environmental changes, and ecosystem services.

69 Table 5.1. Descriptions of categories of environmental changes resulting from mitigation techniques. Environmental Change Description Ambient water quality improvements Improvements in water quality stem primarily from reduced soil erosion and sedimentation due to the presence of stabilizing vegetation, and therefore reduced input of sediment and associated minerals and nutrients to waterways. Organic carbon and bacterial inputs can also be decreased through the exclusion of grazing or loafing animals from riparian areas, for example, when riparian vegetation is present as opposed to open fields or grass. Increased baseflow also improves stream temperatures and can reduce pollutant concentrations (though not load). Vegetation uptakes nutrients and traps sediments. Maintenance of in-stream flows Less variable in-stream flows typically result from increased path lengths for overland flows, reduced flow velocities, and increased storage, infiltration, and percolation of water through soils when nature-based techniques are used, as opposed to more traditional engineered structures that are designed to speed flows. This results in more sustained baseflows and, potentially, decreased peak flows for streams. Increased groundwater infiltration Increased infiltration and percolation of precipitation through soils can also replenish groundwater. This results from increasing land surface permeability and slowing the movement of water across the landscape. Increased green/open space Use of nature-based techniques often involves the establishment of natural open space or green space, as opposed to development. More natural landscapes also, in turn, can affect flows across the landscape and water quality. Improved fish and wildlife habitat / biodiversity Improvements in water and air quality and in habitat availability, connectivity, and quality resulting from landscape changes (e.g., reforestation, forest creation, wetland creation) additionally improves habitat for plants and fish and wildlife. With improved habitat quality, the abundance and diversity of biological organisms can increase as more food sources and space for foraging and reproduction is created. Mitigation located farther from hazards (e.g., traffic and the potential for vehicle collisions) reduce wildlife fatalities relative to mitigation that may be closer to hazards. Air quality improvements Increased open space and vegetated land cover can lead to air quality improvements in several ways. In particular, established vegetation decreases wind erosion leading to reduced particulate matter in the air, purifies the air by converting carbon dioxide into oxygen, and can moderate ambient temperatures. Carbon sequestration and storage Vegetation growth leads to the capture and sequestration of carbon dioxide in the tissues of plants and in soils, thereby reducing atmospheric concentrations of this greenhouse gas. Soil stabilization / reduced erosion Changes in land management and use often result in changes to soil composition, including nutrient status and structure. Forest restoration and creation practices and land restoration projects can fix nutrients into the soil, improving the overall organic matter content and structure, ultimately reducing erosion. Increased forest biomass / tree canopy Increasing the number and density of trees at a given site will lead to more biomass from trees, which contributes to better air quality and carbon sequestration and storage, as well as a greater tree canopy as the forest matures. Decrease in local air temperatures Increased forest canopy, in particular, helps to reduce local air temperatures.

70 Table 5.2. Description of categories of co-benefits resulting from environmental changes. Co-benefit Description Water supply maintenance When in-stream flows are maintained and groundwater is replenished more regularly, streams and groundwater that serve as drinking supplies are more available and less susceptible to variations in water demand or perturbations such as drought. Similarly, maintaining water in the system can provide a passive source of irrigation and offset the need for external irrigation sources. (“New” supply may be subject to water rights resolution before consideration as a co-benefit for a party.) Improved drinking water quality Drinking water can be improved when ground and surface water undergo additional filtration, soil is stabilized and erosion reduced, or streams are improved because of the mitigation. Improved human health and welfare Improvement in water and air quality, as well as increased opportunities for outdoor recreation, can lead to health benefits (e.g., reduced incidences of adverse health effects) and a better quality of life. Also influenced by landscape aesthetics and recreation opportunities. Increased or improved recreational opportunities With increased open space and wildlife habitat, opportunities for recreation, including fishing, walking/hiking, and birdwatching are increased if these areas are accessible or improve populations of species that support recreation in accessible areas. This co-benefit can refer to an increase in availability of recreational opportunities, an increase in the quality of recreational experiences, or both. Resource harvesting Presence of vegetation can lead to resource harvesting, including timber, food, and other materials, either in an organized fashion or by individuals. Improvements in ambient water quality can lead to increased fish abundance and, in turn potentially increased fishing catch. These changes may lead to benefits to commercial fishing and timber/forest product harvest. Improved landscape aesthetics Increased open / green spaces can be viewed as aesthetic improvements which are generally valued by society. Such improvements may manifest in higher property values for homes and businesses in sufficient proximity. Climate stabilization Trees, wetlands, and some plant species have the potential to sequester carbon, resulting in less carbon in the atmosphere and benefits associated with mitigating climate change-related damages. Other environmental changes may reduce greenhouse gas emissions, resulting in less climatic variability. Climate resiliency Climate resiliency can occur if a project improves the ability of the landscape to withstand the effects of climate change, including increased temperatures, magnitude and frequency of storm events, flooding, and drought. Certain environmental changes and ecosystem service benefits contribute to the ability of a landscape or community to withstand climate-related damages. For example, risks of algal blooms increase with rising temperatures. Improvements to water quality resulting from the mitigation techniques can buffer the effects of rising temperatures by improving the baseline environmental conditions at a site. Similarly, increasing tree canopy can reduce the effects of climate change on local landscape and water temperatures.

71 5.2. Screening Assessment of Co-benefits and Costs of Mitigation Techniques The ecosystem service co-benefits screening analysis is step 8B of the overarching decision framework described in Figure 3.1. The screening analysis follows a systematic process for identifying and evaluating site-specific co-benefits likely to emerge from a given mitigation technique or range of mitigation alternatives. The screening includes identification of relevant, site-specific factors that contribute to formulation of co-benefits, evaluation of the relative magnitude of those co-benefits, and comparison of those co-benefits with mitigation costs. While not a formal benefit-cost analysis, which generally requires more time, resources, and expertise, the screening assessment is designed such that DOT staff may readily characterize, compare, and communicate the relative environmental and socioeconomic outcomes of mitigation alternatives. This assessment protocol involves the following substeps of step 8B. 8B1. Establish the project context for co-benefits and cost evaluation. This includes the mitigation project purpose and planning context in which costs and co-benefits are being considered. 8B2. Identify potential co-benefits through established causal chains. Based on the mitigation technique(s), the State DOT selects relevant, generalized causal chains (provided in this chapter), and then evaluates the specific pathways outlined in those chains based on site-specific factors characterizing the environmental and socioeconomic characteristics of the site. This process establishes the set of possible site-specific co-benefits. As noted in Section 5.1, the State DOT may be able to rule out or rule in a mitigation technique by considering the site-specific factors that influence whether a given ecosystem service is relevant for a mitigation alternative. In order for the State DOT to keep track of which ecosystem services are relevant for a given site, the DOT may reference a check-box table (also provided in this chapter) for each of the ecosystem services that have the potential to be provided by each mitigation technique. Co-Benefit Description Non-use values Non-use values are the benefits people gain from a resource outside of any direct or indirect use of the resource, for example for recreation or consumption. This may include values held by the general population related to increased growth in the population of an endangered or threatened species or from conservation of particular habitats (e.g., forests). Cultural values Cultural values reflect spiritual values held by particular segments of the population. They often are related to habitat and biodiversity benefits, or the historical or cultural significance of a species or site to a sub-population. Increased property values In addition to experiencing the benefits listed in this table, individuals may also express the value they place on these co-benefits through an increase in property values associated with increased demand. In most cases the increased demand may be associated with improved landscape aesthetics; however, property owners may also place value on other benefits, including proximity to recreational opportunities or clean air and water.

72 8B3. Assess the relative magnitude of the co-benefits. Based on available information, the co-benefits are ranked in terms of their likely importance.6 Where straightforward, co- benefits may be quantified and/or monetized to facilitate ranking. At the screening stage, a relative understanding of the magnitude of the various co-benefits (in terms of dollars or BRIs) based on readily available data may be sufficient for purposes of estimating the likely range of benefits for a set of alternative mitigation techniques. For some analysis contexts, this may be the last step an analyst decides to undertake. 8B4. Evaluate costs at a screening level. Where mitigation costs are applicable to the analysis context, at the screening stage, generating rough estimates of costs based on readily available data may be sufficient for purposes of estimating the likely range of costs of a set of alternative mitigation techniques. Costs of various mitigation techniques may include long-term maintenance costs in addition to capital costs. 8B5. Compare costs and benefits across alternatives to rank mitigation options based on project objectives. For analysis contexts that include decision-making across multiple mitigation alternatives or understanding the balance of costs versus co-benefits of a given mitigation application, this step would include both a comparison of the magnitude of costs and co-benefits of a given mitigation alternative as well as the magnitudes across mitigation alternatives. The five steps of the screening process are described in more detail in the following sections. Each section also provides the specific tools State DOTs will need to perform screening-level analysis by mitigation technique. These steps address the co-benefits and costs of mitigation alternatives and do not include the benefits and costs of the transportation project that needs impact mitigation. 5.2.1. Establish the Project Context for Co-benefits and Cost Evaluation (Step 8B1) The context in which DOT is evaluating costs and co-benefits of mitigation alternatives matters. The first step the State DOT should take is to define the context in which co-benefits evaluation is taking place as this will dictate both the extent to which co-benefits are evaluated, and potentially how they are evaluated, as depicted in Figure 5.2. Specific questions DOTs should answer to help establish project and analysis context include: • What is the purpose and objective of this analysis? Defining a purpose and objective of the analysis before initiating the work will result in better-targeted analysis and relevant output. For example, is the State DOT evaluating co-benefits to simply justify a mitigation application? Is it seeking cost-sharing opportunities? Is it considering a range of options, each of which could potentially work for purposes of mitigating stream flows? • Is the mitigation being analyzed to facilitate benefit-cost analysis? Are mitigation costs relevant to this analysis for some other reason? If formal benefit-cost analysis is required, DOT may need to undertake all five steps described in this section, which may 6 Importance in this context refers to the likely magnitude of the co-benefit, not the stated value expressed by a potential stakeholder or project partner. While stakeholder values are important, NCHRP 840 discusses a weighting approach that can be used to consider alternative mitigation techniques based on stakeholder preferences.

73 require engaging economics experts. If no, the analyst may decide only to work through steps 8B1-8B3. • Are alternative types or locations for the same mitigation technique being considered? For example, do the mitigation alternatives include wetland restoration at multiple different sites? If yes, and the DOT wishes to understand the relative co-benefits at each site, carefully consider the site-specific ecological and socioeconomic characteristics described in step 8B2 to facilitate a rigorous comparison of the project alternatives. • Are mitigation applications across multiple mitigation techniques being compared for their co-benefits and/or costs? If yes, the analyst should develop an understanding of the unique causal chains of specific mitigation techniques before studying site-specific factors that may result in co-benefits. • Does the mitigation technique or site have specifically relevant regulatory requirements that should be considered in the analysis? If yes, see Section 5.4 for more guidance. • Are any external partners or stakeholders involved in the assessment? If yes, see Section 5.5 for more guidance. • Are the outputs of the assessment targeted to a specific audience? If yes, consider what co-benefits matter to specific audiences, the level of detail that should be included in the assessment, and how the results will be communicated. Figure 5.2. Factors to consider in establishing the mitigation context. 5.2.2. Identification of Co-Benefits through Established Causal Chains (Step 8B2) In this step, the State DOTs select one or more generic causal chains from the set of predefined options, and then evaluate the relevance of the ecosystem service co-benefits within the chain based on site-specific factors of the mitigation alternatives. This process identifies the potential co-benefits stemming from the mitigation technique(s) that the State DOTs have identified. The

74 extent to which the co-benefits of any given technique need to be evaluated are likely to be variable, dependent on the context established in step 8B1, including who potential collaborating external partners/stakeholders are, whether they may be providing matching funding for the mitigation, and what their priorities may be. However, the second step in the screening stage of co-benefits evaluation involves carefully considering the causal chains for the range of mitigation techniques being considered.7 This principally involves considering the specifics of the site and project. Site specifics are relevant both to identification of the baseline conditions and to the specific linkages between the mitigation, the relevant environmental changes, and the ecosystem service benefits that stem from those changes. For example, is the mitigation site located in an arid or wet environment? Is a given environmental change linked to the technique? Will the environmental changes lead to the expected set of ecosystem service benefits? If so, how? The following subsections present generic causal chains for each mitigation technique. The causal chains represent how mitigation of a certain type may lead to ecosystem service co-benefits; not every pathway along the diagram is necessarily relevant to every mitigation application. These diagrams are followed by tables identifying site-specific ecological factors that contribute to the provision of these ecosystem services as well as the site-specific socioeconomic factors that contribute to the value of ecosystem services. These factors help to establish whether a given co- benefit is likely to be relevant for a given mitigation application. This approach attempts to be comprehensive with respect to the types of ecosystem services relevant to each mitigation technique, but it may be that the DOT is aware of other types of co-benefits that may result from a mitigation application. In that case, the DOT should include these additional co-benefits in the accounting of co-benefits. For example, if an invasive plant or animal population is prevalent in a given community and is harming native flora and fauna that are aesthetically or culturally important to the community, a project that removes the invasive species and restores native habitats may warrant specific attention in the co-benefits analysis. 5.2.2.1. Wetland Restoration and Creation Figure 5.3 presents a generic causal chain for how wetland restoration or creation can result in environmental changes and ecosystem services. The types of co-benefits associated with wetland projects may include improved drinking water quality, water supply maintenance, increased or improved recreational opportunities, improved landscape aesthetics, improved human health and welfare, climate stabilization, climate resilience, increased property values, and increased commercial fishing opportunities. Table 5.3 identifies the ecological and socioeconomic factors that determine whether these co-benefits are relevant to a given project. These wetland ecosystem services are described in greater detail in Boyer and Polasky (2004). Note that the colors and patterns of the lines linking the various boxes in these conceptual diagrams are intended to facilitate tracking the linkages between the various boxes. 7 WBSMT, discussed in NCHRP Report 840, includes parameterization of beneficial uses and a set of broad categories of ecosystem services; but the model requires users to parameterize it based on user priorities. It is possible that priority ranking could be informed by the establishment of causal chains. However, it is also possible that establishing causal chains might highlight ecosystem services at a different level of detail or resolution. Ultimately, use of causal chains within the context of this guidance is intended to highlight co-benefits of value to the public, as opposed to specific stakeholders.

75 Figure 5.3. Generic causal chain for wetland restoration and creation mitigation.

76 Table 5.3. Site-specific factors for wetland restoration and creation mitigation. Co-Benefit Site-specific ecological factors that contribute to the provision of ecosystem services Site-specific socioeconomic factors that contribute to the value of ecosystem services Improved drinking water quality • Baseline water quality (where water quality is already high, the water purification properties of wetlands may be less valuable) • Wetland plant type and vegetation management, which can affect potential and extent of reduction in pollutants in surface and groundwater • Size of wetland project • Designated use of hydrologically connected water bodies (e.g., connection to existing or potential drinking water sources) • Availability of substitute water sources (value is increased where substitutes are scarce) • Size of population served by interconnected water supply Improved human health and welfare • See “improved drinking water quality” co- benefit for factors associated with drinking water • Level and type of wetland vegetation that may filter air pollutants (e.g., forested wetlands would have a relatively high potential for air quality benefits) • See “improved drinking water quality” co-benefit for factors associated with drinking water • Proximity of project site to areas where people live, work, and gather • Size of population in airshed Increased or improved recreational opportunities • Number and type of fish and wildlife benefiting (survival, reproduction, and population persistence for recreationally important species) • Size and quality of wetland generated • Size and quality of adjacent green/open space • Potential change in flow or cleanliness of downstream waterways with recreation potential • Accessibility of site to users by type (e.g., fishing, hunting, wildlife viewing, hiking) • Number of users or trips for recreation • Geographic extent of recreational opportunities improved (e.g., acres or stream miles) Improved landscape aesthetics • Potential change in water transparency or color in waterways visible to the public • Anticipated vegetation mix in wetland • Potential change in sediment levels • Potential change in trophic status (biological productivity) • Size and quality of wetland and adjacent green/open space generated relative to what landscape is replaced • Number and type of properties within view of project site • Number of baseline users benefiting from higher quality trips; number of new users attracted to a site for aesthetic reasons

77 Co-Benefit Site-specific ecological factors that contribute to the provision of ecosystem services Site-specific socioeconomic factors that contribute to the value of ecosystem services Water supply maintenance • Soil type and wetland design, which can affect the wetland’s ability to absorb precipitation and flows, maintain baseflows in adjacent streams, or promote infiltration and replenish alluvial aquifers • Designated use of hydrologically connected water bodies (e.g., connection to existing or potential drinking water or irrigation water sources) • Availability of substitute water sources (value is increased where substitutes are scarce) • Baseline variability in water supply levels • Size of population served by interconnected water supply Climate stabilization • Newly created freshwater wetlands may serve as a net source of carbon due to methane emissions, or a net benefit by reducing carbon emissions by restoring disturbed or degraded wetlands • Newly created and restored saltwater wetlands can provide a net carbon benefit (reduced carbon emissions) • Carbon sequestration potential of wetland and timeframe anticipated (available biomass, soil carbon, standing dead carbon) • Baseline level of wetland disturbance that could have contributed to greenhouse gas emissions (wetland type, exposure of soil carbon to oxygen) • Size of wetland (area available for sequestration) • Not applicable Climate resiliency • Relative vulnerability of the ecosystem and environmental conditions to the effects of climate change (e.g., sensitivity of native plants and animals to storms, flood, drought, or increased temperatures); sites that are more vulnerable may benefit more from projects that improve the ability of the ecosystem to withstand these effects • Relative vulnerability of infrastructure and human populations to the effects of climate change (e.g., risks associated with storms, flood, drought, or increased temperatures)

78 Co-Benefit Site-specific ecological factors that contribute to the provision of ecosystem services Site-specific socioeconomic factors that contribute to the value of ecosystem services Non-use and cultural values • Ability of wetland to improve fish and wildlife habitat or biodiversity for species that are protected (e.g., ESA-listed species) or enjoy historical or cultural significance (i.e., via provision of vegetation as a food source and more clean water) • Location of project relative to man-made hazards (e.g., traffic and the potential for vehicle collisions), projects located farther from hazards reduce wildlife fatalities • Proximity of populations that have cultural values for species benefiting Commercial fishing (resource harvesting) • Ability of wetland to improve fish habitat or biodiversity (i.e., via provision of vegetation as a food source and more clean water) • Connectivity of wetland to streams and other waterways (i.e., no impediments to fish passage) • Maintenance of stream flows and improved water quality • Connectivity of waterways with increased fish stocks to commercial fishing catchments • Number of commercial fishing operations with demand for increased fish catch Increased property values • Wetland type and visibility • Number of residential properties with a view of or in proximity to the wetlands Wetlands can affect water supply maintenance and water quality, depending on their characteristics. For instance, soil type and design can affect a wetland’s ability to absorb precipitation and flows, maintain baseflows in adjacent streams, or promote infiltration and replenish alluvial aquifers. Wetland plant type and vegetation management can affect the reduction and sequestration of pollutants. For example, in the Wetland Solute Transport Dynamics (WETSAND) model, vegetation, slope of the site, and lateral and vertical hydraulic conductivities are characteristics of wetlands considered when modeling surface and groundwater interactions (Kazezyilmaz-Alhan and Medina 2008). The extent to which these ecological factors translate into benefits for the public depends on how well the wetland and adjacent water bodies are connected to water supply sources, the size of the population served by the interconnected water supply, existing levels of water treatment necessary, and the uses supported by the water supply (e.g., drinking water, irrigation, etc.). A cleaner drinking water supply can also provide improved health and welfare benefits to the public. The ability of a wetland to improve water quality is highly related to vegetation management (Thullen, Sartoris, Walton 2002). Wetland plant type and management of those plants can affect the potential and extent of reduction in pollutants destined for surface and groundwater, ultimately improving drinking water quality. The connectivity of the cleaned water source to drinking water supplies and the size of the population served by the water supply ultimately determine if and how higher quality drinking water positively impacts human health

79 and welfare. Furthermore, vegetated wetlands can improve air quality – also contributing to improved human health. Wetland projects also have the potential to increase the quantity and quality of recreational trips under certain conditions. From an ecological perspective, recreational activities may be improved for users that seek wildlife viewing opportunities if the project impacts the survival, reproduction, or population persistence of a species sought after during trips.8 Users with an interest in water- based activities may benefit if the wetland project alters the flow or cleanliness of downstream waterways with recreation potential. However, none of these ecological characteristics will necessarily contribute to co-benefits of the project if the site is not accessible to users. An important determinant in understanding how likely a project is to translate into improved recreational experiences is to quantify the number of potential users that will experience these benefits. Wetlands projects also may result in improved landscape aesthetics. Research from France suggests that the health and function of wetlands is highly correlated with the aesthetic values held by people (Cottet et al. 2013). In the study’s context, the wetland aesthetic values are strongly influenced by water transparency and color, the presence and appearance of aquatic vegetation, the presence of sediments, and trophic status. The extent to which these correlations also hold for residents of the United States is unknown. Improved aesthetics may also arise if the wetland mitigation alters a viewshed that results in increased scenic quality.9 These ecological changes will only translate into co-benefits if the public views these changes. Therefore, the number of people within view of the project area – including the number of residential properties with visible access to the site as well as the number of users that travel to the project area – are also necessary considerations when predicting the potential for this benefit to occur at a particular wetland project site. Research demonstrates that the proximity to and the size of certain types of wetlands influences property values and that these relationships may vary by wetland type (e.g., Mahan et al. 2000, Bin 2005). Related research finds that survey respondents have a positive willingness-to-pay to restore or be located near wetlands (Boyer and Polasky 2004). However, this research is generally unable to decipher which ecosystem services property owners and survey respondents are considering when establishing these values. For instance, it is possible that property owners value the improved aesthetics provided by wetlands or perhaps the increased water quality potential or recreational opportunities. More likely, respondents place a value on some combination of these ecosystem services. Constructed and natural wetlands provide habitat for fish and other wildlife through their offering of plants and adequate water supply necessary to sustain and promote life (Knight 1997). Where these improvements lead to an increased quantity and diversity of fish species, downstream commercial fishing activities may benefit if the wetlands are connected with established commercial fishing or shell fishing zones. Similarly, if the fish and wildlife benefiting from the project are protected or have historical or spiritual importance, the project may create benefits 8 See more information on how the InVEST model considers habitat quality here: http://data.naturalcapitalproject.org/nightly-build/invest-users-guide/html/habitat_quality.html# 9 See more information on how the InVEST model considers scenic quality provision here: http://data.naturalcapitalproject.org/nightly-build/invest-users-guide/html/scenic_quality.html#

80 through non-use or cultural values. State DOTs should consider the proximity of populations that enjoy these non-use or cultural values. Wetlands projects have the potential to provide climate stabilization benefits, but not in all cases. Certain characteristics of wetlands – namely type of wetland, available biomass, soil carbon, and standing dead carbon – may create an enabling environment for carbon sequestration.10 However, the carbon fixation process is linked with the ability of a wetland to emit greenhouse gases, including methane, potentially offsetting the carbon sequestration benefits (Bridgham et al. 2006). A significant body of literature exists focusing on the complexity of wetland carbon cycles, identifying circumstances under which wetlands may act as a net carbon source or a net sink (i.e., whether they emit more than they sequester or vice versa) (see, for example, Neubauer 2014, Moomaw et al., 2018, and USGCRP 2018). Freshwater wetlands may emit significant amounts of methane (CH4), a powerful greenhouse gas, under certain circumstances (dependent upon age and level of disturbance). However, restoration of disturbed or drained freshwater wetlands, as may be a focus of stormwater mitigation applications, can lead to net reductions in carbon emissions. Saltwater wetlands generally serve to sequester more carbon than they emit. The effects of increasing atmospheric carbon contribute to damages globally; that is, the global- scale damages of climate change are independent of the sources of carbon emissions. Thus, there are no site-specific socioeconomic characteristics of projects that influence the impact of increased atmospheric carbon (i.e., the marginal climate-related damages associated with an additional unit of carbon in the atmosphere are not dependent on the emissions or sequestration source). Finally, wetlands may offer climate resiliency co-benefits. For example, expanded and/or enhanced wetlands contribute to improved water quality and habitat conditions to support native species and biodiversity. Such ecosystems are more resilient to the effects of climate change. Climate change degrades water quality and increases temperatures, increasing the risk of harmful algal blooms. The healthier the natural ecosystem, the better able it is to withstand these climate- related stressors. 5.2.2.2. Forest Restoration and Creation Figure 5.4 demonstrates the causal linkages associated with forest restoration or creation projects. While the specific environmental changes that precipitate the co-benefits vary, as previously described, many of the categories of potential co-benefits derived from these projects are similar to those of wetland projects. These co-benefits relate to positive changes in drinking water quality, human health and welfare, recreational opportunities, landscape aesthetics, non-use and cultural values, timber and forest products harvest benefits (resource harvesting), climate stabilization, 10 See more information on how the InVEST model considers carbon sequestration potential in coastal wetland environments here: http://data.naturalcapitalproject.org/nightly-build/invest-users- guide/html/coastal_blue_carbon.html#

81 climate resilience, and property values.11,12 Table 5.4 identifies the ecological and socioeconomic factors that determine whether these co-benefits are relevant to a given project. Because of the time it takes for some forests to mature, some of the co-benefits of forest restoration and creation projects may not be relevant in the short term. That is, some of the benefits described below and in Table 5.4 are associated with mature forests and therefore should be viewed as future benefits. For example, forest recreation, aesthetics, habitat, and carbon sequestration benefits are all greatest once the forests have matured. Co-benefit categories that are not likely to occur in the short term following implementation of the mitigation are noted in Table 5.4. 11 Causal chain diagrams specific to forest projects with other main objectives (e.g., fire, recreation, and timber management) are available here: https://nicholasinstitute.duke.edu/project/ecosystem-services-toolkit-for-natural- resource-management/forest. 12 The U.S. Department of Agriculture provides an overview of the ecosystem services forests can provide here: https://www.fs.fed.us/ecosystemservices/pdf/Watershed_Services.pdf.

82 Figure 5.4. Generic causal chain for forest restoration and creation mitigation.

83 Table 5.4. Site-specific factors for forest restoration and creation mitigation. Co-Benefit Site-specific ecological factors that contribute to the provision of ecosystem services Site-specific socioeconomic factors that contribute to the value of ecosystem services Increased or improved recreational opportunities • Number and type of fish and wildlife benefiting (survival, reproduction, and population persistence for recreationally important species) • Number of acres of forest generated • Presence / absence of adjacent or connected forested tracts • Potential change in flow or cleanliness of downstream waterways with recreation potential • Some recreational benefits associated with more mature forests (e.g., hiking, wildlife viewing) may be long-term benefit that increase as the forest matures, but may not be substantial in the short term • Anticipated or potential recreational uses of created forest • Proximity of project site to users • Access/use restrictions • Presence of similar substitutes • Length of walkable trails available • Acres of forest available for recreational activities (e.g., hunting, hiking) • Number of users or trips for recreation Improved landscape aesthetics • Number of trees planted, and acres of forest established relative to the baseline land cover • Tree species mix and density • Length of time until stand maturity (aesthetic improvements may be long- term benefits as the forest matures but not relevant in the short term) • Potential change in flow or water clarity of downstream waterways visible to the public • Number and type of properties within view of project site • Number of baseline users benefiting from higher quality trips; number of new users attracted to the site due to aesthetics Improved drinking water quality • Baseline water quality (where water quality is already high, the water purification properties of forests may be less valuable) • Size of forest project • Potential for decreased sedimentation and pollutant transport into waterways (e.g., via riparian buffers, where width and type of vegetation, waterlogging and organic content of soils, hydraulic conductivity, soil nutrient content regulate nutrient flow, slope, soil type, proximity of forest to waterway) • Designated use of hydrologically connected water bodies (e.g., connection to existing or potential drinking water sources) • Availability of substitute water sources (value is increased where substitutes are scarce) • Size of population served by interconnected water supply

84 Co-Benefit Site-specific ecological factors that contribute to the provision of ecosystem services Site-specific socioeconomic factors that contribute to the value of ecosystem services Improved human health and welfare • See “improved drinking water quality” co-benefit for factors associated with drinking water • Potential of chosen tree species to absorb air pollutants (sulphur dioxide, ozone, nitrogen oxides, particulates) • Potential for tree canopy to decrease local air temperatures • See “improved drinking water quality” co-benefit for factors associated with drinking water • Proximity of project site to areas where people live, work, and gather • Size of population in airshed Timber and forest product harvest benefits (resource harvesting) • Specific mix of tree species • Connectivity of forest to larger forested tracts • Potential for targeted resources to grow/live in forest • Some resource harvesting benefits associated with more mature forests may be long-term benefits that increase as the forest matures, but may not be substantial in the short term • Potential for resource harvesting (i.e., hunting) to conflict with other land uses • Proximity to roads / potential for site access Climate stabilization • Carbon sequestration potential of tree species planted, baseline soil carbon level, and adjacent available biomass (climate stabilization may be a long- term benefit as carbon sequestration rates increase with tree biomass, but may not be substantial in the short term) • Not applicable Climate resilience • Relative vulnerability of the ecosystem and environmental conditions to the effects of climate change (e.g., sensitivity of native plants and animals to storms, flood, drought, or increased temperatures, including localized temperatures); sites that are more vulnerable may benefit more from projects that improve the ability of the ecosystem to withstand these effects • Relative vulnerability of infrastructure and human populations to the effects of climate change (e.g., risks associated with storms, flood, drought, or increased temperatures) Increased property values • See “improved landscape aesthetics” co-benefit • Visibility of clear-cut from timber harvest • Number and type of properties within view of forest project site

85 Co-Benefit Site-specific ecological factors that contribute to the provision of ecosystem services Site-specific socioeconomic factors that contribute to the value of ecosystem services Non-use and cultural values • Ability of forest to improve wildlife habitat or biodiversity for species that are protected or enjoy historical or cultural significance (i.e., via provision of vegetation as a food source, more clean water, habitat space) • Location of project relative to man- made hazards (e.g., traffic and the potential for vehicle collisions), projects located farther from hazards reduce wildlife fatalities • Proximity of populations that have cultural values for species benefiting Forest projects can create new recreational opportunities or improve existing recreational trips. The quantity or quality of recreational trips may increase if a forest project benefits the survival, reproduction, and population persistence of wildlife for which recreationalists have viewing or photography interests. Forest projects may also provide hiking opportunities if their scale is large enough to attract recreationalists, where the scale should be considered relative to the presence or absence of adjacent or connected forested tracts. Users interested in waterways activities will benefit if a forest project has the potential to improve the hydrology or water quality of downstream waterways with recreation potential. How these ecological features translate into co- benefits ultimately depends on how users will interact with the project or adjacent areas. Important considerations include the proximity of the site to users, access and use restrictions of the parcels, the presence of similar substitute recreational sites, the new area made available for recreation, and the number of users or trips that will be affected. Forest projects may also improve landscape aesthetics. Research demonstrates that the public values vegetated areas over non-vegetated areas, particularly where trees provide the vegetation, and especially because of the potential of trees to beautify a space (Dickerhoof and Ewert 1993). How forest projects contribute to improved aesthetics is linked to the number of trees planted, the amount of forest established, tree species mix, and the length of time to maturity of the stand and canopy. Forest projects also have the potential to improve aesthetics if they alter the hydrology or improve the water quality of a downstream waterway visible to the public. Analysts should also consider the number of properties with views of the site with improved aesthetics as well as the number of users that may also experience the enhanced views. Forests can also play a critical role in improving drinking water quality by stabilizing soil and reducing erosion. In general, forests are more likely to capture available water to serve the local ecosystem as opposed to improving flows serving as water supply for human consumption (Muys et al. 2014). In other words, forests do not necessarily make more water available for human consumption but are important vehicles for providing higher drinking quality water to catchments. The ecological characteristics of forests that facilitate improved drinking water quality include the slope, soil type, and proximity of the forest to a waterway, which can affect the forest’s ability to promote infiltration, maintain baseflows or alluvial aquifer recharge, and decrease

86 sedimentation and pollutant transport into the waterway. The extent to which these ecological features translate into benefits for the public depends on whether the water source is connected to drinking water destinations, the water rights context, the number of people served by the water source, and other socioeconomic characteristics. The ability of the forest to clean water also has the potential to result in improved human health and welfare. The characteristics of forested riparian buffers that can clean the water on its way to drinking water sources include width and type of vegetation, waterlogging and organic content of soils, hydraulic conductivity, and soil nutrient content (Correll 1996). Forests can also improve air quality by reducing pollutants in the airshed. Trees remove air pollutants through their plant surfaces, including their leaves (Nowak et al, 2014), making the tree species chosen for the project of particular importance for determining the likelihood that a forest project will result in air quality and human health benefits. Human welfare can also be increased through forest projects where the tree canopy results in decreased local temperatures (Dickerhoof and Ewert 1993). By moderating local temperature, the public may also reduce their use of fossil fuel for energy generation. The analyst should consider the number of people served by the water- and airsheds, among other socioeconomic characteristics of the project site, when determining if these ecological features will translate into co-benefits. Large forest projects may offer opportunities for harvesting timber and other forest products. If harvest rights are available to the public, then analysts should consider the ecological characteristics of the project site that may be desirable to gatherers, including the specific mix of tree species made available and potential for those new resources to grow in the tract. Another form of harvest from forests could be hunted animals or gathered food. In addition to understanding if the forest parcel can be used for these purposes, analysts will also want to analyze the connectivity and proximity of the forested tract as well as substitute locations that provide similar harvest potential. Through their role in providing food and habitat for a variety of wildlife species, forests can also provide benefits through non-use and cultural values associated with those species. It may also be the case that the trees, woods, and forests themselves are associated with historical or cultural reverence for which sub-populations may place value. For example, local populations may have special knowledge or a relationship with the type of forests or forest products that thrive at a site (Tabbush 2010). These values may be difficult to recognize and will require the State DOT to gain a better understanding through discussions with local populations. Forest projects may contribute to climate stabilization through their role in carbon sequestration. Forests are major contributors to carbon fixation and carbon pools globally (Ryan et al. 2010). The carbon sequestration potential of a project site is related to the tree species planted, age of the trees, baseline soil carbon level, and adjacent available biomass. Research also demonstrates that the diversity of tree species at a given site is positively correlated with biomass production (Gamfeldt et al. 2013) and, therefore, carbon sequestration potential. Various resources exist to help quantify carbon sequestration rates in forests under different parameters (e.g., Smith et al. 2006). Available case studies from other forest management projects can also provide a useful

87 framework for evaluating the site-specific attributes of State DOT projects that may result in climate stabilization benefits.13 A variety of forest attributes may also translate into higher property values for nearby residents (Kim and Johnson 2002). Research demonstrates that properties located nearer a forest site have higher property values; however, the presence of clear-cut sites has a negative effect on property values. The types of tree species present may also affect property values. Other research demonstrates that most of the increases in property values are associated with enhanced scenic beauty, not necessarily a value placed on other amenities provided by forests (Kim and Wells 2005). 5.2.2.3. Stream Stabilization, Restoration, and Improvement Figure 5.5 presents the causal chain for stream stabilization, restoration, and improvement projects. Based on the types of environmental changes that could occur following one of these projects, the following co-benefits are possible: improved drinking water quality, improved human health and welfare, water supply maintenance, increased or improved recreational opportunities, commercial fishing (resource harvest), non-use and cultural values, climate stabilization, and climate resilience. Table 5.5 identifies the site-specific ecological and socioeconomic factors that would determine if these co-benefits might be the outcome of a particular State DOT project. For instance, streams stabilized with vegetation that reduce pollutants and sediments in surface water may result in improved human health and welfare benefits (Dosskey et al. 2010). The soil erosion potential of a given stream buffer is also an important consideration, therefore soil type, soil density, and density of root structures will also play a role in how stream projects contribute to cleaner drinking water (Wynn 2004). As in all project cases, the analyst will also need to consider if and how the improved water quality will ultimately result in improved drinking water quality and, if so, quantify the number of people who might benefit. These same ecological features are likely to contribute to water supply maintenance as well. In addition to water quality benefits, stream rehabilitation projects can also contribute to improved water supply through in-stream flow improvements through reduced erosion and degradation and enhanced interaction with groundwater. Streams play a vital role in sustaining aquifers throughout the United States (Colvin et al. 2019). The potential for a State DOT project to contribute to water supply maintenance depends on the connectedness of the project stream with water supply catchments. When determining the potential benefits to the public, the analyst should also consider baseline variability in water supply levels, the reliability and availability of substitute water supply sources, and the number of people in the water supply network when evaluating the improvement incremental to the project. 13 For example, the NESP guidebook offers this example from a U.S. Department of Agriculture forest management project: https://nespguidebook.com/wp-content/uploads/2018/10/Chapter3- EstimatedValuesofCarbonSequestrationResultingfromForestManagementPolicyScenarios_v1.pdf.

88 Figure 5.5. Generic causal chain for stream restoration and improvement mitigation.

89 Streams may also provide climate stabilization benefits where vegetative buffers provide carbon sequestration services and/or carbon cycling that occurs within the stream bed itself (Larson and Harvey 2017). The extent to which this stream restoration alternative results in carbon sequestration benefits depends on the choice of vegetation during project design. While aquatic vegetation is likely to have carbon sequestration benefits, the benefits are plant species-specific and likely minimal relative to the benefits associated with larger vegetation, especially trees. The change in carbon sequestration potential of the stream following restoration requires information on lateral transport of carbon, which is a function of flow and water chemistry data. The U.S. Geological Survey describes detailed approaches to considering carbon sequestration in various ecosystems, including aquatic systems (USGS 2010). Improved or restored streams may also result in increased or improved recreational opportunities under certain conditions by increasing the value of water-based recreation trips. More dramatically, water flows could be improved in a way that creates new recreation opportunities by opening new waterways to water-based activities. Stream improvements may also result in increased fish and other water-based life that attracts recreational fishers. Ultimately, the analyst will need to consider the size and scope of the stream and the project site to determine the likelihood that the project will result in measurable recreation benefits. Similarly, the analyst should also consider recreation demand, the availability of other nearby recreation opportunities, and the number of potential users and trips that might experience the benefits. Streams can also provide food and habitat for fish and other riverine species with commercial fishing potential. To determine the ability of a stream to provide harvest benefits, the analyst will need to consider the ability of the stream to attract and retain harvestable species (e.g., through the creation of habitat suitable for spawning and rearing), the number and type of fish benefiting, and the connectedness of the project stream to other fish habitat and catchment locations. The analyst will also need to understand the harvest rights context of the stream as well as which recreational or commercial fishers may have demand for the fish species of interest. Projects that improve streams may also be associated with increased non-use and cultural values. Rare or revered fish species may have non-use values associated with their existence (e.g., wild salmon); similarly, larger species that feed on the species of fish may also be a source of non-use values that should be considered (e.g., orcas). The streams themselves may also be culturally important and significant for local populations, including native populations (Colvin et al. 2019). An analyst should consider which populations may hold these benefits and their proximity to and knowledge of the project. Carbon can also be fixed in the water column as well as sediments within and around streams, resulting in climate stabilization benefits; however, like wetlands, streams can also be a source of greenhouse gas emissions (Marx et al. 2017). When determining if the improvements to a stream via the State DOT project will result in a net reduction or increase in atmospheric carbon or other greenhouse gases, an analyst will need to consider mechanisms associated with the carbon cycle including surface area of the stream, turbulence and flows, properties of the sediment that affect storage, biomass around the stream, and carbon inputs into the system.

90 Table 5.5. Site-specific factors for stream stabilization, restoration, and improvement mitigation. Co-Benefit Site-specific ecological factors that contribute to the provision of ecosystem services Site-specific socioeconomic factors that contribute to the value of ecosystem services Improved drinking water quality • Baseline water quality: existing upstream or downstream water quality impairments (where water quality is already high, further improvements may be less likely or less valuable) • Extent of streambank stabilization and erosion prevention elements of the mitigation (e.g., nature and extent of riparian planting) • Designated use of hydrologically connected water bodies (e.g., connection to existing or potential drinking water sources) • Availability of substitute water sources (value is increased where substitutes are scarce) • Size of population served by interconnected water supply Improved human health and welfare • See “improved drinking water quality” co- benefit for factors associated with drinking water • See “improved drinking water quality” co-benefit for factors associated with drinking water Water supply maintenance • Interconnectivity of surface water with alluvial groundwater • Baseline variability in water supply levels • Size of population served by interconnected water supply Increased or improved recreational opportunities • Number and type of fish and wildlife benefiting (survival, reproduction, and population persistence for recreationally important species) • Overall size of restored stream • Potential change in flow or cleanliness of downstream waterways with recreation potential • Ability of stream to attract and maintain fish populations (e.g., food sources, shelter) • Length of streams impacted and available for recreation • Designated use of the stream • Type(s) of recreation possible given the size of the stream • Accessibility of site to users • Number of users or trips for recreation Commercial fishing (resource harvesting) • Number and type of fish benefiting (survival, reproduction, and population persistence of commercially valuable fish and shellfish) • Ability of stream to attract and maintain fish populations (e.g., food sources, shelter) • Accessibility of stream to other fish habitat • Fishing rights context (e.g., who can fish and where, collection limits, etc.) • Demand for harvest and use of fish and shellfish among local population • Number of commercial fishing entities benefiting

91 Co-Benefit Site-specific ecological factors that contribute to the provision of ecosystem services Site-specific socioeconomic factors that contribute to the value of ecosystem services Non-use and cultural values • Ability of project to improve habitat for and therefore populations of protected or culturally important fish species • Presence of other larger species with protections or cultural significance that prey on the directly benefiting fish species • Changes in the quality or status of a stream where local populations hold cultural values • Location of project relative to man-made hazards (e.g., traffic and the potential for vehicle collisions), projects located farther from hazards reduce wildlife fatalities • Proximity of populations that have cultural values for species benefiting Climate stabilization • Carbon sequestration potential of stream and timeframe anticipated (available biomass, carbon in stream bed, turbulence, and flow) • Baseline level of stream disturbance that could have contributed to greenhouse gas emissions (stream type and size, stream flow rates, amount and type of vegetation) • Size of stream and adjacent stream beds (area available for sequestration) • Not applicable Climate resilience • Relative vulnerability of the ecosystem and environmental conditions to the effects of climate change (e.g., sensitivity of native plants and animals to storms, flood, drought, or increased temperatures, including localized temperatures); sites that are more vulnerable may benefit more from projects that improve the ability of the ecosystem to withstand these effects • Relative vulnerability of infrastructure and human populations to the effects of climate change (e.g., risks associated with storms, flood, drought, or increased temperatures) 5.2.2.4. Uplands Restoration Figure 5.6 presents the generic causal chain for uplands restoration projects. The co-benefits that may flow from a particular project include improved drinking water quality, improved human health and welfare, water supply maintenance, increased or improved recreational opportunities, non-use and cultural values, improved landscape aesthetics, increased property values, climate stabilization, and climate resilience (Bonn et al. 2009). Table 5.6 describes the site-specific ecological and socioeconomic factors that would encourage these co-benefits among uplands restoration projects.

92 Figure 5.6. Generic causal chain for uplands restoration mitigation.

93 Table 5.6. Site-specific factors for uplands restoration mitigation. Co-Benefit Site-specific ecological factors that contribute to the provision of ecosystem services Site-specific socioeconomic factors that contribute to the value of ecosystem services Water supply maintenance • Ability of landscape to transport clean water towards drinking water catchments or promote infiltration relative to pre-restoration land use • Ability of landscape to enhance base flow and aquifer recharge • Designated use of hydrologically connected water bodies (e.g., connection to existing or potential drinking water sources or irrigation water sources) • Availability of substitute water sources (value is increased where substitutes are scarce) • Baseline variability in water supply levels • Size of population served by interconnected water supply Improved drinking water quality • Flood reduction, soil stabilization and filtration by vegetation and soil • Baseline water quality (where water quality is already high, the water purification properties of uplands may be less valuable) • Plant type and vegetation management, which can affect potential and extent of reduction in pollutants in surface and groundwater • Size of uplands project • Designated use of hydrologically connected water bodies (e.g., connection to existing or potential drinking water sources) • Availability of substitute water sources (value is increased where substitutes are scarce) • Size of population served by interconnected water supply Improved human health and welfare • See “improved drinking water quality” co-benefit for factors associated with drinking water • See “improved drinking water quality” co-benefit for factors associated with drinking water Increased or improved recreational opportunities • Overall size of restored uplands area • Vegetation type • Length of time until maturity of new plant species • Number and type of fish and wildlife species benefiting with wildlife viewing potential • Inclusion of trails as part of uplands restoration • Proximity to population centers • Land use / ownership considerations • Number of users who may increase their use of the project site or experience an improved trip Improved landscape aesthetics • Number and type of new plant species introduced • Length of time until maturity of new plant species (aesthetic improvements may be long-term benefits but not relevant in the short term) • Number of acres of natural landscape restored • Number and value of properties within view of restored landscape • Number of baseline users benefiting from higher quality trips; number of new users attracted to the site due to aesthetics

94 Co-Benefit Site-specific ecological factors that contribute to the provision of ecosystem services Site-specific socioeconomic factors that contribute to the value of ecosystem services Non-use and cultural values • Ability of project to improve habitat for and therefore populations of protected or culturally important wildlife species • Changes in the quality or status of a landscape that has cultural value for local populations • Location of project relative to man- made hazards (e.g., traffic and the potential for vehicle collisions), projects located farther from hazards reduce wildlife fatalities • Proximity of populations that have cultural values for species benefiting Increased property values • See “improved landscape aesthetics” co-benefit for factors associated with viewshed • Number of residential properties with a view of new, natural landscapes Climate stabilization • Carbon sequestration potential of vegetation planted, baseline soil carbon level, and adjacent available biomass (climate stabilization may be a long-term benefit as vegetative biomass mature but may be less substantive in the short term) • Not applicable Climate resiliency • Relative vulnerability of the ecosystem and environmental conditions to the effects of climate change (e.g., sensitivity of native plants and animals to storms, flood, drought, or increased temperatures); sites that are more vulnerable may benefit more from projects that improve the ability of the ecosystem to withstand these effects • Relative vulnerability of infrastructure and human populations to the effects of climate change (e.g., risks associated with storms, flood, drought, or increased temperatures) Uplands restoration projects can improve water supply maintenance if the uplands can better transport clean water towards drinking water catchments or promote infiltration relative to pre- restoration land use. In this case, an analyst should carefully consider how the infiltration potential of the uplands will change with the project, since land restoration activities can result in variable flow outcomes and the chosen landscape can take a variety of formats. The analyst should also consider how the adjacent water source is used and whether it is connected to drinking water destinations in addition to the scale of this water source relative to other water sources that contribute to overall water supply.

95 Where an uplands restoration project is likely to result in water supply maintenance, it also has the potential to improve the health and welfare of the public through the provision of cleaner water. Like forest restoration projects, the analyst should consider whether the vegetation used in uplands restoration has the potential to reduce contaminant sources and to clean the water destined for drinking water sources. Not only may the vegetation provide water filtration properties, but the vegetation may also stabilize soil and reduce erosion destined for water sources under baseline conditions. To better understand how relevant this co-benefit is for a site or project, the analyst should also understand how the public may ultimately benefit from the improved water supply, including through the connectivity of the site, the availability of substitute sources, and the number of people in the water catchment area. Some uplands restoration projects may also increase recreation potential or improve existing recreational trips. This may be the case if the uplands were restored with vegetation with desirable viewing qualities and if the project site is large enough to accommodate and attract users. Additionally, some uplands restoration projects may include trails or walkways that actively promote recreation. When uplands restoration projects alter or enhance water flows, downstream water-based recreation activities may also benefit. Finally, the connectivity of the project site to population centers as well as the land ownership and use rights of the parcel are important considerations when determining whether an uplands restoration project is likely to result in increased or improved recreational opportunities. Projects that restore uplands areas are likely to improve habitat and food sources for wildlife species, some of which may be associated with non-use and cultural values. Analysts should consider which wildlife species may derive population or quality of life benefits from the project and the extent to which the public values their existence beyond any direct use. Similarly, it may be the case that local populations experience a cultural value associated with these wildlife species or the landscapes they inhabit. Improved aesthetics can also result from uplands restoration projects. Natural landscapes can provide a “wilderness” experience or an escape from other less natural viewsheds that may be valued by users as well as nearby property owners (Bonn et al. 2009). The type, mix, and maturity of the vegetation planted as well as the size of the area offering potential viewing pleasures at the project site should provide an indication of whether the public may benefit from improved aesthetics. Research also demonstrates that property owners in urban watersheds place a premium on residential lots with upland wildlife habitats with the highest ecological values (Netusil 2006). Moreover, like the other mitigation techniques that alter particular landscapes, the property owners may have a greater demand for living near the improved aesthetics or any of the other co- benefits generated by a project, resulting in increased property values in the vicinity of the project site. The extent to which the property values increase as a result of a project will likely be influenced by the density and number of properties near the project site. Like forest projects, uplands restoration projects can contribute to climate stabilization if the mix of vegetation – including trees and shrubs – results in carbon sequestration. Abundant research suggests that returning human-altered landscapes to more natural conditions results in greater carbon sequestration in soils, including in grassland environments (Potter et al. 1999), agricultural lands that have transitioned to natural or perennial vegetation (Post and Kown 2000), and others.

96 An analyst should consider the baseline land use relative to the newly restored landscape when determining whether carbon sequestration may be a benefit of a given project site. 5.2.2.5. Agricultural Practices Modification and Land Conversion As discussed in Section 3.2, the agricultural practices modification and land conversation mitigation category captures a broad set of potential techniques and strategies. For instance, agricultural practices on cropland that could be modified include but are not limited to fertilizer techniques and application levels, tilling technology, crop rotation, and weed control practices whereas practices on range land include grazing patterns and frequency. Each of these changes in practices may result in different environmental changes, ultimately resulting in a unique set of co-benefits. Therefore, in addition to accounting for site-specific factors that may influence co- benefits, the DOT staff will need to consider the specific agricultural practices modified. Given the variation in mitigation techniques that fall into this category, this guidance does not incorporate a generic causal chain. Instead, State DOTs may reference conceptual diagrams relevant to specific agricultural practices, projects, and sites. Figure 5.7, Figure 5.8, and Figure 5.9 guide how the co-benefits of particular agricultural practices modification projects may be analyzed based on existing causal chains. Specifically, these causal chains are similar to those presented above, and demonstrate similar relationships between the environmental changes and ecosystem service benefits; however, these diagrams were developed to evaluate ecosystem service benefits of agricultural conservation practices that improve water quality and manage nutrients (nitrogen and phosphorus). (The numerical label numbers in the figures are specific to the source and have no meaning for this report.) Figure 5.7. Example causal chain diagram for agricultural conservation mitigation with the goal of enhancing water quality (Source: This diagram is Figure 1 from Wainger et al. (2017)). Table 5.7 highlights some considerations across agricultural mitigation techniques in the context of a screening assessment. The text below describes some of the potential ecological and

97 socioeconomic factors that could be affected by a State DOT project. For instance, modifying some agricultural practices may result in better maintenance of the local water supply, both from the perspective of maintaining water within the agricultural system (i.e., for irrigation purposes) as well as filtering or moderating the flow of water destined for drinking water purposes. Similarly, some modified agricultural practices – including reductions in the use of pesticides, fertilizers, herbicides, or manure as well as changes in tilling techniques that reduce soil erosion – have the potential to increase water quality and reduce the need for treatment before incorporating into a drinking water supply (Parris 2011).14 Figure 5.8. Example causal chain diagram for nitrogen management practices (Source: NESP (2020)). Some agricultural practice modification projects could also result in improved human health and welfare. For instance, projects that reduce chemical runoff to groundwater and surface water systems may lead to less ingestion of harmful chemicals via contaminated water, increasing 14 The U.S. Geological Survey explains how pesticides contaminate groundwater here: https://www.usgs.gov/special-topic/water-science-school/science/pesticides-groundwater?qt- science_center_objects=0#qt-science_center_objects

98 overall well-being of water consumers. A reduction in application of harmful chemicals can also benefit the farm workers who apply them, due to less skin contact and inhalation and the potential to avoid the adverse effects of close contact with regulated chemicals. Another potential pathway towards improved health and welfare is the production and harvest of more nutritious crops, either by changing the composition of crop or the soil minerals and water content taken up during the crop growth cycle (Carmen Martinez-Ballesta et al. 2008). Changing the mix of practices employed in an agricultural system may result in crop productivity benefits and increased yields or incomes for farmers. This co-benefit may be less likely than the other co-benefits described in this section given farmers may already be maximizing production or profits before the State DOT project. However, the project may enable the farmer to invest in practices previously outside of a farmer’s budget or technical constraints, in which case the farmer may experience the resource harvest benefits relative to baseline levels. Apart from agricultural production, changes in the composition of crop or grazing land may also increase the number and type of wildlife available for hunting or harvesting, providing benefits to hunters. Figure 5.9. Example causal chain diagram for phosphorous management practices (Source: NESP (2020)).

99 Table 5.7. Site-specific factors for agricultural practice modification mitigation. Co-Benefit Site-specific ecological factors that contribute to the provision of ecosystem services Site-specific socioeconomic factors that contribute to the value of ecosystem services Water supply maintenance • Potential of modified agricultural practices to reduce demand for external sources of irrigation (e.g., diverted flows, groundwater, etc.) • Potential of modified agricultural practices to result in reduced overland flows, increased infiltration of precipitation, and more consistent flows of water for drinking water purposes • Designated use of hydrologically connected water bodies (e.g., connection to existing or potential drinking water sources) • Availability of substitute water sources (value is increased where substitutes are scarce) • Baseline variability in water supply levels • Size of population served by interconnected water supply • Number of farms or volume of crops (e.g., acres or values) benefiting Improved drinking water quality • Potential for modified agricultural practices to result in improved water quality (e.g., reduced fertilizer use, reduced pesticide or fertilizer runoff due to cover crops, reduced sedimentation) • Designated use of hydrologically connected water bodies (e.g., connection to existing or potential drinking water sources) • Availability of substitute water sources (value is increased where substitutes are scarce) • Size of population served by interconnected water supply Improved human health and welfare • See “improved drinking water quality” co- benefit for factors associated with drinking water • Potential for modified agricultural practices to result in more nutritious selection and composition of crops • See “improved drinking water quality” co-benefit for factors associated with drinking water • Size of consumer base for agricultural products from project site

100 Co-Benefit Site-specific ecological factors that contribute to the provision of ecosystem services Site-specific socioeconomic factors that contribute to the value of ecosystem services Increased agricultural yields (resource harvesting) • Potential for improved agricultural practices to result in increased crop or livestock yields (note that in some cases, changes in agricultural management practices may reduce crop yields, for example no-till and cover crops) • Number of farmers benefiting • Number of farms or volume of crops (e.g., acres or values) benefiting Increased wildlife hunting/harvesting (resource harvesting) • Potential for modified agricultural practices to result in increased wildlife presence, which could lead to increased wildlife hunting/harvesting • Hunting rights context • Numbers of harvesters benefiting Climate stabilization • Potential for improved agricultural practices to reduce carbon emissions (machinery, agro-chemical use, soil disturbance) • Potential for improved agricultural practices to increase ability of soil to store carbon • Not applicable Climate resiliency • Relative vulnerability of the ecosystem and environmental conditions to the effects of climate change (e.g., sensitivity of native plants and animals to storms, flood, drought, or increased temperatures); sites that are more vulnerable may benefit more from projects that improve the ability of the ecosystem to withstand these effects • Relative vulnerability of infrastructure and human populations to the effects of climate change (e.g., risks associated with storms, flood, drought, or increased temperatures) Carbon emissions from agriculture are generated from machinery used to cultivate cropland, the application of agro-chemicals, and the disturbance of soil resulting in soil organic carbon oxidation (West and Marland 2002). If an agricultural practice modification project results in changes to practices that minimize these activities, then carbon emissions will be reduced, resulting in a climate stabilization benefit. Agricultural soils can also serve as sites for carbon sequestration under certain management practices, including no-till or less-intensive tillage practices, changes in crop rotation, restoring degraded soils, and land conversion (Antle and McCarl 2001). Also included in this category are agricultural land conversion projects, or instances where agricultural land is taken out of rotation temporarily or permanently. For projects of this nature, the guidance for the uplands restoration or forest restoration or creation mitigation techniques may provide the most useful starting point for considering co-benefits as well as the site-specific ecological and socioeconomic factors. When adopting the guidance for those mitigation techniques, the analyst should consider the changes relative to baseline agricultural land.

101 5.2.2.6. Tracking Ecosystem Services Co-Benefits To facilitate tracking the specific set of ecosystem services provided by each of the mitigation techniques, Table 5.8 presents a template table assembled from each of the technique-specific causal chains. The DOT may construct its own similar comparison table, as follows: • The columns of the table should specify the mitigation alternatives being compared. The alternatives may include various mitigation techniques (some uplands restoration, some streambank stabilization), or it may include multiple alternative projects based on the same out-of-kind mitigation technique (e.g., three different wetland restoration alternatives). • The table should include all categories of potential co-benefits across the mitigation options, as well as an “other” category to record anything that may be specific to a given project and warrant consideration. The DOT will check off the categories of co-benefits expected to result from a mitigation application after weighing the site-specific factors, such as those described in the tables above. • In addition to selecting which co-benefits are most likely, the table also provides space (“Descriptor” columns) to describe the potential benefit based on consideration of the site- specific factors for each mitigation application. For the screening-level comparisons, this column may simply make a qualitative note about why the co-benefit is relevant, for example, “hydrologically connected to a drinking water source” or “increases habitat availability for waterfowl.” Where data are available, and DOT anticipates additional information would be helpful for decision-making, the Descriptor columns may include quantitative information on the benefit based on socioeconomic or environmental outcomes, for example, “hydrologically connected to drinking water source serving 150,000 people,” “additional 15 acres of waterfowl habitat.” • The table includes a row to specify mitigation costs for comparison across mitigation techniques (as described in step 4 below). Ultimately, this table may be as simple or detailed as is helpful to DOT to achieve its objectives for understanding mitigation co-benefits.

102 Table 5.8. Identifying relevant co-benefits by mitigation technique. Co-benefits Mitigation techniques Wetland restoration, creation Forest restoration, creation Stream stabilization, restoration, and improvement Uplands restoration Agricultural practices modification and land conversion Y/ N Descripto r Y/ N Descripto r Y/ N Descripto r Y/ N Descripto r Y/ N Descripto r Improved human health and welfare Water supply maintenanc e Improved drinking water quality Increased landscape aesthetics Increased or improved recreational opportunitie s Climate stabilization Climate resiliency Non-use and cultural values Increased property values

103 Co-benefits Mitigation techniques Wetland restoration, creation Forest restoration, creation Stream stabilization, restoration, and improvement Uplands restoration Agricultural practices modification and land conversion Y/ N Descripto r Y/ N Descripto r Y/ N Descripto r Y/ N Descripto r Y/ N Descripto r Commercial fishing benefits (resource harvest) Timber and forest products harvest benefits (resource harvest) Other resource harvest benefits Other Estimated project costs Notes: Blue cells highlight the co-benefits that may be anticipated from a project characterized by a particular mitigation technique per the causal chain diagrams presented earlier in this chapter. Because causal chains are not identified for agricultural practices modification and land conversion, that mitigation technique is included as a column without narrowing the suite of potential co-benefits given the wide range of projects that could fall under this umbrella (see main text for details).

104 5.2.3. Assess the Relative Magnitude of Co-Benefits (Step 8B3) After identifying relevant co-benefits for each mitigation alternative based on the causal chains and site-specific project characteristics, the State DOTs may wish to conduct a more detailed assessment of the likely importance and/or magnitude of each co-benefit identified. This step involves consideration of the specific site-specific factors that may serve as BRIs, indicators of the magnitude of the potential co-benefits. The process may rely on a range of information sources and evaluation techniques, from rules-of-thumb to estimating monetary values, with the aim of understanding the likely scale and relative importance of co-benefits for the proposed mitigation technique. BRIs, in an economics context, are measurable indicators that capture the connection between environmental changes and how people benefit from those changes (NESP 2016).15 Therefore, BRIs should not only describe the environmental changes themselves, but should ideally reflect socioeconomic factors, including the demand for the changes, how those changes will be used or valued, substitute and complementary services, and accessibility. While these indicators likely do not reflect the full monetized or quantified benefit of a given environmental change, BRIs fulfill two important objectives: • Communicate accessible and comprehensible measures that the public can understand and use. • Enhance the accuracy of the evaluation by employing easily identified information that does not require significant effort or assumptions to calculate. Because BRIs should consider both the environmental changes as well as site-specific socioeconomic conditions, the chosen indicators should be project-specific. However, many projects with related co-benefit categories ultimately will rely on a similar set of BRIs. Table 5.9 identifies options for BRIs for each co-benefit described in this guidance and identifies their relevance across mitigation techniques. Analysts may also consider other indicators not included among these examples, particularly when the data are available or when specific stakeholders may have an interest in better understanding how a project might impact specific metrics. After deciding which BRIs are the most appropriate for a mitigation technique or project site, State DOTs will reference available data sources to populate these indicators. Some of the BRIs require quantification to gain a sense of magnitude. These data may be available from state or local governmental agencies (e.g., for indicators related to public recreation), utilities (e.g., for indicators related to water quality and supply), accessors’ offices (e.g., for indicators related to properties), or industry (e.g., for indicators related to resource harvest among private companies). In some instances, the most relevant BRIs may require projecting future values (e.g., number of 15 The discussion of best practices for producing BRIs for analysis from NESP is reproduced here: https://nespguidebook.com/assessment-framework/what-are-benefit-relevant-indicators/ What’s it worth? Quantifying monetary values for all ecosystem service co-benefits is resource and data intensive. Benefit-relevant indicators (BRIs) are measurable indicators that provide stakeholders with meaningful information to compare co-benefits across mitigation alternatives

105 new users), in which case an analyst should first determine if such analysis is feasible and, if so, what assumptions are most tenable. Ideally all BRIs would be quantitative measures and reflect demand for the expected change in ecosystem service associated with the mitigation application. However, measuring BRIs in this way for all of the categories of co-benefits for all mitigation alternatives would be data- and time- intensive and require expertise that DOT staff may not have accessible (e.g., wildlife biologists to predict species and habitat outcomes, agricultural and resource economists to evaluate recreational or commercial demand for the species benefiting). As a result, the BRIs described in Table 5.9 emphasize the objective of relying on easily identified information and therefore reflect a mix of quantitative and qualitative indicators to communicate the value of the co-benefits. For example, accessibility of a restored forest to populations that hold cultural or spiritual values for forests or forest products is a qualitative characterization given the difficulty in measuring a quantitative BRI for this co-benefit category. Of note, climate resiliency benefits are gained through improvements in other ecosystem services, such as water quality, species and habitat/biodiversity, and trees/vegetation that reduce local temperatures. These resilience benefits may theoretically be measured in terms of reduced climate-related damages, for example to infrastructure, crop productivity, or health risks. However, quantifying how the projects reduce the vulnerability of ecosystems and communities to the effects of climate change is complex and beyond the scope of a screening analysis of these mitigation techniques. Thus, while identifying the potential for projects to improve climate resiliency of a site may provide useful information, this guidance does not identify separate BRI metrics to estimate the magnitude of this benefit. The indicators (whether quantified BRIs or qualitative descriptions) may be entered into the “Descriptor” columns in the co-benefits matrix per the template in Table 5.8. At this stage, an analyst may choose to use information on co-benefits to develop a relative ranking of preferences across the mitigation options based on the co-benefits and project costs. Ranking may prove challenging where BRIs are not directly comparable, so an analyst will need to use best judgment regarding which types of co-benefits are desired within the project context described in step 8B1. Additionally, in comparing mitigation alternatives using the mix of BRIs and other metrics to indicate co-benefits, it is important not to implicitly double-count benefits. Where ecosystem service co-benefits are related (i.e., when they flow from one into another along a pathway in the causal chain), the metrics used to describe the benefits are not necessarily additive. For example, property value benefits may stem from improved landscape aesthetics. Health benefits stem from drinking water quality improvements. The connection between these co-benefit categories is clear in Table 5.8 because the BRIs describing them overlap. However, analysts should be careful not to sum related co-benefits. DOT should leverage available site-specific data sources for these metrics. USEPA’s EnviroAtlas provides useful environmental spatial data (https://www.epa.gov/enviroatlas).

106 Table 5.9. Summary of potential benefit-relevant indicators by co-benefit and mitigation technique. Co-benefit Potential benefit-relevant indicators Mitigation techniques Wetland Forest Stream Uplands Ag* Improved drinking water quality Number of people in the watershed experiencing benefits (service area of drinking water supply)      Total decrease in contaminants or sediment in drinking water supply      Reduction in water treatment (e.g., sediment and nutrient removal) costs      Improved human health and welfare Number of people in the watershed experiencing benefits (service area of drinking water supply)      Number of people in the airshed experiencing benefits   Number of people living or recreating in areas experiencing increased tree canopy/reduced local temperatures    Volume or value (market price) of increased production of nutritious agricultural products  Water supply maintenance Number of people served by interconnected water supply (service area of drinking water supply)     Reduction in variability in water supply levels (e.g., avoided days or likelihood of water use bans)      Reduction in irrigation costs  Improved landscape aesthetics Number and type of properties within view of project site    Number of users benefiting from higher quality trips due to aesthetics; number of new users attracted to the site   

107 Co-benefit Potential benefit-relevant indicators Mitigation techniques Wetland Forest Stream Uplands Ag* Increased or improved recreational opportunities Number of new (increased) or existing (improved) land- based users (e.g., hunters, hikers, wildlife viewers)     Number of new (increased) or existing (improved) water- based users (e.g., swimmers, recreational fishers, recreational boaters)     Number of recreational trips generated (increased) or with higher value (improved)     Size of the area opened for recreation or providing more valuable recreational opportunities (stream miles, acres, length of trails, etc.)     Resource harvesting Amount or market value of fish available for catch by commercial fishing industries   Number of commercial fishing businesses benefiting from improved catch   Volume or market value of timber or other forest products available for harvest  Number of timber harvesters benefiting from increased access to forest products  Volume or market value of agricultural yield increase attributable to the project  Number of agricultural producers benefiting from improved yields  Increased property values Number of residential properties expected to experience property value effects   

108 Co-benefit Potential benefit-relevant indicators Mitigation techniques Wetland Forest Stream Uplands Ag* Non-use and cultural values Number and type of fish and wildlife benefiting for which the public may hold non-use values (e.g., threatened or endangered species or species of local, cultural import)     Accessibility to populations that hold cultural or spiritual values for the site (e.g., restored forest) or benefiting resources (e.g., fish or forest products)     Climate stabilization Amount or value (social cost of carbon) of carbon sequestration possible due to mitigation technique      Amount or value (social cost of carbon) of greenhouse gases emissions reduced due to mitigation technique    Agricultural practices modification.

109 5.2.4. Screening Evaluation of Costs (Step 8B4) Perhaps even more than potential co-benefits of a mitigation technique (in addition to practical considerations such as land availability for siting stormwater mitigation), cost is likely to be a primary driver of interest in implementing any given mitigation technique or option within a mitigation technique. Like co-benefits, mitigation costs are also site-specific. In particular, the more earthmoving that is involved, the more costly the mitigation (including associated increases in the planning, design, and implementation costs) relative to less engineered solutions. In addition, any mitigation that requires the purchase or easement of land will have higher costs than other mitigation alternatives without such components and land values can vary significantly across sites. Differences in mitigation approach can significantly influence cost. For example, whether reforestation is accomplished through reseeding versus planting of roots or saplings versus planting of balled and burlapped trees will greatly affect the material and implementation costs.16 As part of a screening analysis, the State DOT should assemble readily available mitigation cost data. This could include information from previous mitigation applications conducted by the State DOT itself, potential external project partners/stakeholders (see Section 3.4), or the restoration or LID/GI literature. These costs may be borne by the State DOTs or shared with its project partners, if applicable. Cost-sharing partnerships can be beneficial for long-term (operations and maintenance) as well as capital costs.) NCHRP Report 840 discusses relevant cost categories for BMPs, which are equally as applicable to mitigation techniques. These categories include: • Land purchase or easement (including factors such as acquisition and transaction costs; as well as opportunity costs, or the monetary benefits foregone when the mitigation application is pursued), • Construction (including planning and potentially remediation, and the cost of capital), • Operation and maintenance, and • Program administration.17 However, additional cost categories that may be significant in the context of mitigation techniques include post-construction efficacy monitoring (particularly in flood sensitive areas), liability/insurance (if public access is a project component), and vegetation/planting (particularly given the prominence of land-based solutions among the mitigation techniques). A 2008 NCHRP report provides guidance on estimating environmental costs of transportation projects, not limited to but including mitigation costs (ICF International et al. 2008). 16 The magnitude of co-benefits may also be variable and dependent on project specifics. In this reforestation example, ecosystem benefits may accrue faster to a reforestation project using grown trees instead of seeds. 17 See NCHRP report 840 (Weinstein et al. 2017) for a more detailed discussion of the overall factors related to BMPs. Region-Specific Cost Differences If relying on cost data for similar mitigation applications, consider whether adjustments are needed to account for region-specific differences in costs of capital and labor (e.g., land value) and changes in real costs of materials over time.

110 In most cases, existing approaches for cost estimation used for traditional stormwater mitigation costing may be applied for purposes of estimating mitigation technique costs; however, cost data from mitigation techniques that have already been implemented in similar settings may also be used to inform cost estimates. In such cases, when existing project examples are used to inform or derive costs, attention should be given to the following aspects of existing project costs: • Major site-specific factors associated with costs. This includes factors that are likely to be key cost drivers, such as land ownership, proximity to roadways for construction access, overarching permitting requirements, etc. In other words, are the site conditions of the example project from which cost data are being derived sufficiently similar to be relevant? • Age of cost data. To the extent that cost data from an example project are older, updating costs to current year dollars may be warranted. While readily available cost deflator tools may be used, including specific construction cost price deflators, a variety of cost deflator data are available from the U.S. Bureau of Economic Analysis at www.bea.gov. As a default, State DOTs may use a construction cost index developed specifically to adjust prices paid by State DOTs for roadway construction materials and services. The FHWA provides a description of and time series data for the National Highway Construction Cost Index (NHCCI) at https://www.fhwa.dot.gov/policy/otps/nhcci/. While the NHCCI includes some cost elements related to mitigation (such as labor and equipment costs), State DOTs may wish to separately consider changes in mitigation cost elements over time that are not reflected in the NHCCI, in particular land purchase. • Regional relevance of cost data. Some categories of mitigation costs vary significantly by region. These regional variations should be taken into consideration when possible. When relying on costs of similar projects, State DOTs should prioritize past project examples within the region. If this is not possible, State DOTs should consider which cost elements may not be transferable across regions and research cost estimates for those elements to refine the overall project cost estimate. For example, while equipment and labor costs may have less variation by region, land values and revegetation costs may vary significantly. Finally, in some cases, a stormwater mitigation application may result in avoiding maintenance costs at specific sites. For example, stream restoration projects may reduce the need for repeated efforts to repair culverts and stabilize banks. Such avoided costs may be captured as “negative costs” when evaluating and comparing mitigation costs. 5.2.5. Compare Costs and Benefits across Alternatives to Rank Mitigation Options Based on Project Objectives (Step 8B5) Once the DOT identifies the specific suite of co-benefits and a reasonable range of costs, co- benefits should be compared to costs. Importantly, at the screening stage, co-benefits are generally not monetized, requiring this comparison in qualitative terms, relying on best judgment (i.e., whether the co-benefits are likely to justify the costs). If the analysis is to compare project alternatives within or across mitigation techniques, then the goal of the assessment is to determine which project alternative provides the greatest magnitude of co-benefits for the least cost identified.

111 In addition to comparing costs against mitigation alternatives, the DOT should evaluate the mitigation technique costs in the context of the overall transportation project costs. Mitigation may be a significant component of a total transportation project cost. This is particularly true, for example, where a transportation project affects prime wetlands or a sole source aquifer. If the costs of a given mitigation alternative are greater than anticipated, this may signal that the DOT should consider whether more efficient mitigation options are available or whether there are opportunities to re-engineer the transportation project to reduce the hydrological impact and therefore the extent of mitigation needed. 5.2.6. Synthesis of Co-benefits Screening Process and Expected Level of Effort The co-benefits screening approach enables analysts to compare multiple mitigation alternatives in terms of the potential ecosystem service co-benefits and relevance to regional planning objectives. Table 5.10 describes the general process, data sources, and expected level of effort for State DOT staff, consultants, and external partners/stakeholders to conduct these types of screening analyses. Following are key considerations for State DOTs regarding the application of this approach: • Spatial analysis skills and software will be helpful in defining project context and evaluating co-benefits. Involving analysts with GIS skills and spatial data awareness can be helpful in establishing the project context and evaluating the ecosystem services co- benefits. • Data accessibility and completeness will vary across locations. The ability to access data that can readily characterize site-specific ecological and socioeconomic characteristics of a given site can vary tremendously. While some data sources are national in scope, other information is better gleaned from local municipalities, and the variability in the completeness and accessibility of these sources can be substantial. • Information from local experts could add significant value to the screening process. Complementing publicly available data sources with information readily available from other sources would provide a more nuanced and complete picture of the potential for co- benefits. • Consider local planning objectives when identifying potential mitigation alternatives. Local planning documents can suggest mitigation techniques or geographic locations that may be more desirable. For example, in the West Branch Housatonic case study (Section 7.2.2.2) local documents encourage wetlands development along currently unprotected waterways. These planning documents may also identify mitigation alternatives that may not align with local planning objectives. For example, conversion of agricultural land to wetlands might be a mitigation technique that is discouraged locally because of an interest in preserving farmland. Integrating regional planning objectives early in the process will enable State DOTs to focus the hydrological and co-benefits screening analyses on the most practicable mitigation alternatives.

112 Table 5.10. Process, data sources, and length of time by co-benefits screening analysis step. Step Process Data sources Length of time involved Step 8B1: Establish the project context Describe the purpose of the mitigation activities and the alternatives under consideration, including the mitigation techniques and sites. Develop an understanding of how these techniques align with local objectives. Identify potential collaborators engaged in projects, policy, or advocacy aligned with the mitigation techniques. Determine any relevant regulatory requirements to engaging in projects at these specific sites. Documents or websites that describe local objectives and long-term plans at the state, county, or municipality level. Federal, state, or local rules around permitting, consultation, etc. that may be required to implement projects at a given site or of a particular type. This step should take about one day of effort. Additional effort may be warranted if the DOT needs to reach out to the identified potential collaborators to clarify objectives or request information used in subsequent steps. Less effort may be required if the DOT already has a deep awareness of the local community and planning context based on other regional projects or public input into the transportation project itself.

113 Step Process Data sources Length of time involved Step 8B2: Identify co- benefits through established causal chains Use the generalized causal chain diagrams provided in Chapter 5 to determine if a mitigation technique may lead to specific ecosystem service co-benefits. Organize findings around site-specific ecological and socioeconomic factors. For this analysis, the research team used the tables from Chapter 5 to organize this information and determine the likelihood of a co- benefit. Spatial data identifying the location of the proposed mitigation alternatives. Publicly available spatial data sets that can be overlaid with proposed mitigation site boundaries, publicly available reports that describe baseline features of the site, and publicly available data about specific nearby sites of interest. In some cases, the analysis that follows points to additional sources of information the DOT could pursue to further characterize the potential for co-benefits. In many cases, additional information could be garnered through local outreach; these examples did not pursue data through outreach. Half-day to a full day for each mitigation technique. Additional time would be required if the DOT engaged in outreach to collect information not readily available through desk research. Less time may be required if the DOT is already familiar with the necessary data sources, including through use in planning the transportation project.

114 Step Process Data sources Length of time involved Step 8B3: Assess relative magnitude of co-benefits Use Table 5.8 from Chapter 5 to summarize findings from step 8B2 by alternative. Include any BRIs or other quantified characteristics identified in step 8B2, include others as the data allows. Table 5.9 from Chapter 5 can help point to specific BRIs of interest by co-benefit and mitigation technique. Presenting the results in one table facilitates ease of assessing relative magnitude of co-benefits. Because our analysis did not consider costs for each example, this is where our analysis ended. In addition to assessing the relative magnitude of co-benefits across alternatives, this step additionally included linking the findings with the local objectives identified in step 8B1. See step 8B2, the same data sources used to determine likelihood that a co-benefit exists are also likely to help assess its magnitude 1-2 hours to summarize findings from step 8B2 and carry over any BRIs or quantified characteristics. Additional time would be required if the DOT wanted to identify additional data sources to describe or convey magnitude of co-benefits. Step 8B4: Screening evaluation of costs Work with potential collaborators, particularly environmental restoration- focused entities, to obtain project descriptions for comparable techniques performed in similar and nearby locations, if possible. Compile and tabulate the overall project costs and costs for key project components, if possible, to generate potential cost ranges. Costs from comparable projects near the proposed sites, likely obtained from potential collaborators or restoration partners. This step not performed for purposes of these case studies, but the research team estimates the time needed to identify and contact collaborators and then review and compile cost data would take one half-day to full day.

115 Step Process Data sources Length of time involved Step 8B5: Compare costs and benefits across alternatives to rank mitigation options based on project objectives Rank techniques based on number and magnitude of co-benefits taking into consideration DOT and collaborator priorities. Not applicable. This step not performed for purposes of these case studies, but the research team estimated the time needed to consider data and rank techniques would be less than one hour.

116 5.3. Detailed Analysis of Co-Benefits and Costs of Mitigation Techniques As described in Section 5.2, the screening analysis approach can range from a relatively simple assessment (identifying which categories of co-benefits are likely relevant to a given mitigation application) to significantly more analytically challenging (researching available data to measure BRIs to quantify the magnitude of the co-benefits) depending on the context of the overall transportation project and mitigation alternative, expertise of the analysts, and time and resources to dedicate to the analysis. If the information provided via the screening analysis is insufficient (i.e., not actionable as described in step 9 of Figure 3.1) for purposes of selecting a mitigation alternative, a State DOT may need or want to conduct a more in-depth evaluation. Detailed analysis of co-benefits falls within step 11 of the overall decision framework provided in Figure 3.1. 5.3.1. Need for Detailed Analysis The most rigorous version of the ecosystem service co-benefits analysis involves estimating monetary values for as many categories of co-benefits and mitigation costs as feasible. Such an analysis is likely to require involvement of experts, both ecologists or biologists to model the environmental changes resulting from a project (e.g., effects on species populations or air and water pollutant concentrations) and economists to quantify the associated values. Each type of co-benefit requires a different type of ecological and economic analysis approach. Accordingly, the DOT would not likely engage in a full detailed economic analysis of mitigation options for every individual transportation project. Such analyses are likely reserved for large or contentious projects, or at the state programmatic or planning level. Circumstances in which State DOTs might need to rigorously evaluate co-benefits include: • Detailed consideration of co-benefits is required, or highly desired, by a mitigation application financial co-sponsor. • Comparisons of co-benefits across a range of mitigation techniques. If comparing across a range of mitigation techniques, the State DOT should focus on co-benefits that are common to multiple techniques to make relative comparisons. In such cases it may be sufficient to focus on the relative magnitudes of key inputs that would be used to monetize benefits without actually completing a full analysis. • Comparisons of co-benefits need to be made to marginal costs (i.e., the marginal cost of a mitigation technique relative to another mitigation technique) or total costs (e.g., when trying to justify conducting the mitigation). In such circumstances, monetization of co- benefits may “tip the scale” in favor of the mitigation technique. Given the variety of models and methods that may be required for a detailed analysis of each co- benefit category, this guidance focuses on providing an overview of relevant methods and models that the DOT may leverage. The two main categories of evaluation are costing and co-benefits analyses. With respect to cost estimation, in most cases the least cost mitigation alternative that achieves the primary goal of stormwater mitigation likely would be considered a default option and the

117 evaluation of co-benefits would justify a specific alternative technique. The mitigation technique alternatives should be sufficiently defined to allow for a more detailed determination of the specific costs (within the same cost categories discussed above) associated with mitigation implementation. The description of cost analysis under step 4 of the screening analysis provides information that may also be used for detailed evaluation. However, instead of referencing costs of representative mitigation applications, to get a more precise estimate of costs for a given application, State DOTs may seek out engineering cost estimates from construction and restoration companies and research project bid estimates. Detailed evaluation of co-benefits can take a variety of forms. To compare across technique types or locations analysts use indicators of co-benefit values (e.g., data that inform the relative magnitude of a monetized value, e.g., the number of households likely to experience a benefit, the relative values for different project attributes, etc.). If necessary, analysts consider using more detailed benefits valuation methods. Where a State DOT is interested in determining simply whether the benefits of a mitigation alternative justify the costs, the DOT may consider a breakeven analysis framework, where the focus is on identifying the threshold at which benefits are equal to costs and determining the likelihood that the collective benefits would meet or exceed that threshold.18 A detailed evaluation of ecosystem service co-benefits requires linking two types of analyses: • Ecological models or ecological production functions, which quantify the extent to which a mitigation application generates environmental changes (e.g., in water, air, and habitat quality, species population benefits, or carbon sequestration rates). • Economic valuation methods, which quantify how people benefit from these environmental changes (e.g., health improvements and recreational opportunities). Ecological models and economic valuation methods are described in the following sections. 5.3.2. Ecological Modeling It is important in the context of a detailed analysis of ecosystem service benefits analysis not to shortcut understanding the environmental changes. Some schedule-based ecosystem service valuation tools provide a range of economic values (e.g., $/acre estimates of wetlands and forests) of ecosystem service benefits of landscape changes without first modeling the site-specific context of the projects. While potentially useful for highlighting categories of potential benefits (as this guidance does more explicitly in the causal chain-based screening assessment approach), models and approaches that do not incorporate a detailed ecological modeling component will not provide sufficient information on the incremental benefits of the mitigation applications to inform decision-making in the context of DOT mitigation planning. A variety of ecological and integrated ecosystem service models exist that the DOT may leverage to evaluate the environmental changes resulting from the mitigation techniques. Some of these models evaluate only a single ecosystem service. For example, the U.S. Army Corps of Engineers 18 In a breakeven analysis benefits are monetized one at a time and compared to costs. Additional benefits may be sequentially monetized until the monetized benefits are greater than the costs. At the point benefits are determined to be greater than the cost of the project no further benefits valuation is needed. However, where the objective is comparing relative benefits across projects rather than identifying whether the benefits justify the costs, breakeven analysis would not be applicable.

118 HEC-WAT focuses on watershed-based water quality modeling and the U.S. Forest Service provides forest ecosystem carbon yield tables for use in calculating forest carbon storage and sequestration benefits.19 Given the breadth and scope of these models, and that only in rare cases will the DOT engage them to evaluate individual project mitigation alternatives, this guidance does not describe all of the available models for every mitigation technique and ecosystem service combination. Instead, this guidance focuses on describing the strengths and limitations of broader ecosystem service models, which are designed to evaluate multiple ecosystem service benefits of projects or activities in an integrated manner. Examples of these models that target relevant ecosystem service benefits are provided in Table 5.11. Important considerations for selecting appropriate models for the DOT to conduct a detailed analysis of ecosystem service co-benefits of mitigation alternatives include the following: • Topical relevance: Inclusion of ecosystem services of relevance to DOT and/or a stakeholder. • Target audience: Focus on providing information for land and resource managers and planners. • Site-specific: Ability to integrate site-specific ecological data. • Project-specific: Ability to conduct project-level analysis. • Reliability: Peer-reviewed and vetted modeling framework. • Transparency: Documentation of model methods and guidance for use. • Accessibility: Open-source platform with user support opportunities. A series of reports developed by Business for Social Responsibility (BSR) evaluate the existing arena of emerging ecosystem service modeling tools (BSR 2015, BSR 2011). While the focus of the BSR’s review was on the utility of the models for measuring dependence of corporations on natural ecosystems and corporate sustainability risks, the evaluation considered several relevant factors described above. A key finding of these reviews is that while these tools are emerging and show promise and a few have generated some published work [Integrated Valuation of Ecosystem Service and Tradeoffs (InVEST) and AIRES], none has yet been subject to the level of technical and peer review that would be desired and emerged as the standard for ecosystem services analysis. Additionally, the more detailed tools focus primarily on the ecological analysis component and exclude economic valuation or include it only in a limited way. The tools that do include economic valuation components do not include sufficient rigor regarding ecological modeling. The high-level finding of the BSR review is that these tools are still emerging and are continuing to be tested, verified, and validated. In the coming years, the DOT may wish to attempt to test or to revisit examples of application of these models. The most promising models for DOT based on the criteria above are InVEST and AIRES. Both are GIS-based platform models designed to evaluate multiple ecosystem services including site-specific data. The InVEST tools include more services and have a more transparent guidebook and user support system. The InVEST model 19 Information on the Army Corps’ water quality models may be found at https://www.hec.usace.army.mil/software/waterquality/ and the Forest Service carbon accounting tools at https://www.nrs.fs.fed.us/carbon/tools/#cct.

119 additionally includes recommendations for data sources to meet the relatively high ecological data requirements for modeling for some services (e.g., water quality). DOT may also be able to reference spatial environmental data within USEPA’s EnviroAtlas for modeling purposes (https://www.epa.gov/enviroatlas). Table 5.11. Examples of ecosystem service benefit modeling tools potentially available for use in quantifying co-benefits. Tool and Developer Description Ecosystem Services Included Availability ** Data Requirements InVEST Natural Capital Project Mapping and valuation models accessed through Arc-GIS • Carbon sequestration and storage • Coastal Protection and Vulnerability • Crop Pollination • Habitat Quality • Timber Production • Aquaculture • Offshore Wind Energy • Recreation • Reservoir Hydropower Production • Scenic Quality • Sediment Retention • Water Purification • Wave Energy Open Source Moderate to high, varying by service ARIES (Artificial Intelligence for Ecosystem Services) Gund Institute for Ecological Economics Modeling framework to map ecosystem service flows • Carbon sequestration and storage • Flood Regulation • Aesthetic views/Open Space • Freshwater Supply • Sediment Regulation • Subsistence Fisheries • Recreation Open Source, web-based High to develop and apply new case studies ESR (Ecosystem Services Review) World Resources Institute Spreadsheet-based process to qualitatively assess ecosystem services, designed primarily to manage business risks and opportunities • Various* Publicly Available Low, relies on qualitative survey process MIMES (Multiscale Integrated Models of Ecosystem Services) Gund Institute for Ecological Economics Dynamic modeling system for mapping and valuing ecosystem services • Various* Open Source, however, access to SIMILE modeling software is required High to develop and apply new case studies

120 Tool and Developer Description Ecosystem Services Included Availability ** Data Requirements SERVES (Simple and Effective Resource for Valuing Ecosystem Services) Earth Economics Benefit transfer tool calculating low and high values by ecosystem service by land cover type • Various* Referenced studies are accessible but full model not yet publicly accessible Low Benefit Transfer and Use Estimating Model Toolkit Dr. John Loomis, Colorado State University Spreadsheets and meta-analysis equations to support benefit function transfer to value changes in ecosystem species and habitat-related ecosystem services • Fishing • Hunting • Wildlife Viewing • Passive Use Values Publicly Available Low * Not all ecosystem service models rely on the same definition of ecosystem services. The models also differ in terms of level of detail with the services evaluated. For example, the ESR framework includes more than 40 separate serves binned based on the 2005 Millennium Ecosystem Assessment categories of provisioning, regulating, and cultural services. The MIMES model defines ecosystem services more broadly in terms of ecological processes (e.g., bioregulation and climate regulation). SERVES considers a broad mix of ecological process (e.g., soil formation) and ecosystem services (e.g., recreation). ** These tools are free (no fee required for use); however, some may have operating system requirements (which evolve) or require certain modeling software (e.g., as indicated for MIMES). 5.3.3. Economic Valuation Methods Most of the integrated ecosystem service models do not emphasize detailed economic valuation methods. Thus, it is likely that if a DOT requires monetized estimates of a subset of ecosystem service co-benefits, it will need to engage the expertise of resource economists to value the environmental changes identified for each mitigation alternative. This section summarizes primary methods that economists employ to value natural resources and environmental changes. However, given the time and resources required, it is unlikely that a DOT will undertake primary research for individual transportation projects. Thus, this discussion describes existing guidance and best practices for secondary valuation methods that leverage existing research for similar policy questions to estimate values of environmental changes. Economists refer to the adaptation of existing research to new policy questions as “benefit transfer” methods. Economic benefits, or “social welfare” benefits, such as those gained through the protection of ecological systems and services, are most commonly expressed in terms of a “willingness-to-pay” (WTP) for a given quantity or quality change and reflect the net economic benefit of a project or policy. WTP measures what individuals would trade for a particular change in quality or quantity of a good or service. For example, individuals may demonstrate positive preference for reduced exposure to water-borne contaminants by expressing that they would be willing to pay a monetized amount to receive this benefit. The WTP estimate therefore reflects the value of this benefit. Social welfare is recognized as the appropriate measure for valuing the benefits and costs of regulatory actions by the Office of Management and Budget (OMB 2003).

121 In the case of many environmental improvements, markets do not exist to provide direct measures of WTP. In these cases, economists utilize two groups of methods to estimate WTP – “revealed preference” methods and “stated preference” methods. “Revealed preference” methods involve observing choices people make in related markets to infer relative values for environmental attributes. For example, travel cost models are often used to estimate recreational use values by examining tradeoffs individuals make between costs of a recreational trip (e.g., fuel, equipment, and time costs) and trip attributes (e.g., water quality at a lake site). Another revealed preference method, hedonic models, relies on statistical analysis to relate the relative contribution of characteristics of a good to its market price. Hedonic studies may be used, for example, to quantify the impact of increased green or open space on the market value of neighboring residential properties by controlling for other factors (e.g., square footage, population density, or quality of school system) affecting the sales price. Avoided cost approaches are frequently used as a proxy for the WTP value of some services: for example, avoided water treatment costs associated with nutrient filtration benefits of wetlands. With respect to health benefits, cost of illness approaches may be used to estimate the economic benefits (avoided costs) of reduced morbidity, for example due to improved air and water quality. The cost of illness approaches may include the direct medical costs associated with an illness, the cost to society resulting from lost earnings, and the value of lost leisure time. While revealed preference studies can capture how people change behavior with respect to the use of a resource, they cannot capture values that do not necessarily affect behavior. For example, an individual may have a positive preference for improving habitat conditions for an endangered species even outside of the personal ability to consume, fish, hunt, view, or otherwise interact with that species. The individual may simply have a positive preference for conserving the species for altruistic reasons or for the enjoyment of future generations. Economists refer to these co- benefits as “non-use values.” (See Table 5.2 for a definition of non-use.) In these cases, “stated preference” methods that involve surveying populations to elicit information on relative preferences for a specific commodity or attribute can be used to estimate WTP. “Stated preference” methods involve surveying populations to elicit information on relative preferences for the commodity or attribute being valued. These surveys ask respondents a series of hypothetical questions to derive information on WTP for a particular benefit. The surveys may be structured in a variety of ways, including direct, open-ended questions focused on an individual’s WTP or choice questions designed to gather information on the relative preferences of individual respondents. Examples of how these primary research methods may be used for the ecosystem service co- benefits relevant to the out-of-kind mitigation techniques, and examples of the data required to implement these methods, are summarized in Table 5.12. Primary research in the form of stated or revealed preference studies require significant time and effort to collect and evaluate original survey responses or behavioral data (e.g., recreational fishing trip behaviors and costs). Likely, even under the more detailed analysis approach, that the DOT would leverage existing research employing these methods to value the co-benefits of the mitigation alternatives.

122 Table 5.12. Ecosystem service co-benefit valuation methods and data requirements. Ecosystem Service Co-Benefit Primary Valuation Methods and Example Data Requirements Improved human health and welfare (e.g., from improved drinking water and air quality) Costs of Illness Analysis: • Type of morbidity risk associated with contaminant/hazard from drinking water, air quality or other health risks • Changes in morbidity rates (i.e., number of affected persons) • Medical expenses for morbidity type • Time losses at work and leisure associated with morbidity type -OR- Avoided Costs: • Reduction in sediment and nutrient loads requiring removal through water treatment • Costs of water treatment Water supply maintenance Avoided Costs: • Reduction in need for accessing alternative water sources for irrigation or drinking water • Costs of accessing substitute water resources Improved landscape aesthetics/ Improved property values Hedonic Analysis: • Measures of relevant environmental change, including: o water clarity before and after project implementation o acres of new wetland or green space • Number of homes experiencing property value benefits (based on geographic location with respect to the project area) • Baseline market values of homes experiencing property value benefits • Regional housing market sales data • Other property attributes potentially affecting value Increased/ improved recreational opportunities Travel Cost Analysis: • Regional options for recreational sites and specific attributes of the sites (e.g., access, water quality, recreational activities supported) o water quality improvement o recreationally valuable species population change (e.g., fish) • Types and levels of recreational use of the water body before and after the project (e.g., trip numbers) • Visitation data from recreationalists (site choice information) • Trip-related travel costs (time and expenditures) Commercial fishing Industry Analysis: • Supply and demand curves for relevant industries • Number of businesses affected • Effect of project on catch levels Non-use and cultural values Stated Preference Surveys: • Environmental change of relevance for valuation (e.g., change in population level or population stability of an endangered species) • Survey data gathered from relevant population regarding WTP for the environmental change Climate stabilization Social Cost of Carbon Estimates: • This analysis typically references existing schedules of marginal effects per unit of atmospheric carbon on climate-related damages – an emerging research area. • Changes in carbon sequestration or emissions levels due to the project

123 Benefit transfer is a method of analysis that relates results from existing, relevant studies to a new policy question when conducting primary research is not feasible or practical. Benefit transfer is an accepted and widely applied technique in resource economics. Analysts take different approaches to benefit transfer, including relying on value estimates from a single existing study or combining results from several existing studies, such as relying on mean or median values or developing mathematical models (i.e., estimating a “value function”). Benefit transfer methods require assessing whether results from previous research can apply to another context. Several sources identify best practices when using benefit transfer (USEPA 2014, Johnston et al. 2015). The OMB Circular A-4 (2003) includes criteria for guiding decisions about the relevance and reliability of benefit transfer. These criteria include the following: • The resource, and the magnitude of change in that resource, should be similar in the existing study and new policy contexts. • The relevant characteristics of the existing study and new policy contexts should be similar. • Existing studies should be based on adequate data as well as sound and defensible empirical methods and techniques. • The existing study and new policy contexts should have similar populations (e.g., demographic characteristics). The market size (e.g., target population) between the existing study site and the new policy site should be similar. • The availability of substitutes across existing study and new policy contexts should be similar. Given the stringent requirements for best practices for benefit transfer, the DOT should engage agency economists or outside consultants with relevant expertise to estimate the economic value of these co-benefits if a detailed analysis approach is required. For more information on benefit transfer methods, see Johnston et al. (2015), Boyle et al. (2010), and Navrud and Ready (2007).