Wetland Mitigation, Volume 2, A Guidebook for Airports (2019)

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46 4.1 Introduction Regulatory agencies require project sponsors to avoid and minimize impacts to the greatest degree practicable, and then provide compensatory mitigation to offset unavoidable impacts. As discussed in Chapter 2, more than one agency (federal, state, and/or local) may take juris- diction over a wetland or water, and a proposed project that affects a jurisdictional wetland or water may require a permit and mitigation from more than one agency. This chapter focuses on functional assessment and types of mitigation available to compensate for unavoidable impacts to jurisdictional wetlands and waters (see Figures 4-1 and 4-2). 4.2 Wetland Functional Assessment The functional value of a wetland is a measure of the services it provides to wildlife, people, and the surrounding environment. Ecosystem benefits provided by wetlands include, but are not limited to, flood control, nutrient farming, wildlife habitat, water filtration, and out- door recreation. A wetland functional assessment is conducted to calculate both the loss in functional value associated with project-related impacts and the value gained following the implementation of wetland mitigation measures, such as wetland protection, improvement, or creation. When conducting a wetland functional assessment, it is important to use the methodology that is applicable to the project’s location and to the agency or agencies that have jurisdiction over the impacted wetlands. Methods for quantifying a wetland’s functional value can vary greatly between states and regulatory agencies. It is also necessary that the selected assessment methodology for the impacted wetland be utilized for the proposed mitigation activity, so that it can be demonstrated that sufficient mitigation is being provided to offset lost functions. The wetland functional assessment, and the development of mitigation, most often are completed during the permitting process. The permit(s) received from the appropriate agency or agencies are generally conditioned to require implementation of a specific mitiga- tion plan with pre-determined success criteria. It is important to note that the mitigation habitat must match the wetland habitat it offsets (USACE 2008). For example, freshwater Forested Wetlands cannot be used to offset impacts to a tidal saltmarsh. The extent to which mitigation must match the impact may vary based on the types of locally important habitats and local regulations. A variety of methods have been developed to assess and quantify wetland function. A com- monly used methodology is called the Wetland Rapid Assessment Procedure (WRAP). WRAP is not used consistently across all states, but it will be used here to provide an example of how such assessments are conducted. To complete WRAP, six parameters are assigned a score between C H A P T E R 4 Mitigation Types

Mitigation Types 47 0 and 3 (Miller and Gunsalas 1997). Half scores (e.g., 2.5) are acceptable. The parameters are defined as follows: • Wildlife Utilization: a measure of observations and/or signs (i.e., scat, tracks, nests, etc.) of wildlife; • Canopy: a measure of the presence, health, and appropriateness of wetland shrub and overstory canopy; • Groundcover: a measure of the presence, condition, and appropriateness of the wetland ground cover; • Adjacent Buffer: a measure of the adjacent habitat support for the wetland; the size and quality of the adjacent uplands; • Hydrology: a measure of the extent to which the amount and duration of standing water is appropriate for the type of wetland being assessed; and • Water Quality and Treatment: a measure of the quality of the surface water flowing into the wetland from adjacent land uses. Figure 4-1. Federally protected wetland at Lincoln Airport. Photo courtesy of Environmental Resource Solutions. Figure 4-2. Federally protected wetland at Lincoln Airport. Photo courtesy of Environmental Resource Solutions.

48 Wetland Mitigation, Volume 2: A Guidebook for Airports As Table 4-1 shows, the sum of the six parameter sub-scores is divided by 18 to obtain an overall quality score between 0 and 1.0. This quality score is then multiplied by the size of the affected area to obtain the functional value of the wetland. This calculation is performed for the wetland as it currently exists and as it will be after the proposed action is complete. The difference in these functional values is either the functional loss that will be incurred when an impact is complete, or the functional gain that will be realized when a wetland is created or improved. A unit of wetland functional loss is called a “debit,” and a unit of wetland functional gain is called a “credit.” The amount of functional value gained by mitigation (credits) must equal the amount of functional value lost by the impact (debits). Note that mitigation determination throughout the country is highly vari- able. While the goal of mitigation is always to replace lost functions and values, the method utilized may change and is constantly evolving. For instance, some USACE regions may utilize wetland type and acreage to determine mitigation requirements in lieu of a detailed functional assessment methodology. 4.3 Wetland Mitigation Options Once it has been determined that wetland mitigation is required, and a functional assess- ment has been completed to determine how many wetland credits are needed, it is necessary to consider the type of mitigation required. This section summarizes three options for wet- land mitigation: permittee-responsible mitigation, mitigation bank credits, and in-lieu-fee mitigation. 4.3.1 Permittee-Responsible Mitigation Permittee-responsible mitigation can occur on the same site as the proposed impact (on-airport mitigation) or on another site purchased or owned by the permittee (off-airport mitigation). With this option, the permittee must demonstrate that the mitigation credits have been generated, and the functional value of the wetland is retained over time. Fulfilling these responsibilities can be risky, time-consuming, and expensive. For example, on-airport mitigation could require the ongoing use of limited airport property to accommo- date the mitigation area, create a hazardous wildlife attractant near aircraft movement areas, and incur substantial costs associated with wetland design, construction, and the establishment of a protective easement on airport property, all of which are usually undesirable. Off-site WRAP Parameters Value Wildlife Utilization 0-3.0 Canopy 0-3.0 Ground cover 0-3.0 Adjacent Buffer 0-3.0 Hydrology 0-3.0 Water Quality and Treatment 0-3.0 Score (Sum/18) 0-1.0 Wetland Size (Acres) Functional Value (Score x Acreage) Source: South Florida Water Management District WRAP. Table 4-1. Table for determining wetland functional value using WRAP.

Mitigation Types 49 mitigation must be created at an appropriate distance from the airport to avoid the creation of a potential wildlife attractant and could incur substantial costs associated with land acquisition, as well as wetland design, construction and monitoring, and the establishment of a protective easement. Therefore, permittee-responsible mitigation is not usually preferable when an alter- native option is available. 4.3.2 Mitigation Bank Credits A mitigation bank is an off-site source of wetland mitigation, generated by a third party (USACE 2008). In this case, the mitigation bank operator, or “banker,” receives the permits to create the bank and demonstrates that wetland “credits” have been generated, making them available for sale. Permittees can purchase credits from a mitigation bank to offset wetland impacts (debits) incurred due to a proposed project. The bank’s credits are gen- erated by wetland restoration, creation, enhancement, and/or preservation methods. The mitigation banker assumes the responsibilities and risks of generating and maintaining the wetland functional value. A mitigation bank may contain multiple wetland habitat types, and therefore may offer multiple kinds of mitigation credits. The cost of credits is based on the amount needed, the type needed, demand for credits in the basin, and price competition from other sources. Each bank has an approved service area and credits can be used to offset wetland impacts only within that designated area. Mitigation banks generally are formed by private investors when local demand for credits is high or increasing. Banks don’t exist in service areas where there is little demand for credits. Cities, counties, state agencies, utility companies, or other entities may also form mitigation banks to offset their own project- specific impacts. The permittee must be sure to purchase credits that will offset the wetland impacts for all applicable agencies (local, state, and federal). Federal regulations establish a flexible prefer- ence for using mitigation bank credits (when available) over permittee-responsible mitigation because banks consolidate the mitigation for multiple impacts in a centralized location, increas- ing the ecological value of the mitigation (USACE 2008). In many cases, the purchase of wetland credits from a mitigation bank is an attractive and more affordable option for airport operators, as they are not required to undertake the effort and expense associated with wetland design, construction and ongoing monitoring. 4.3.3 In-Lieu-Fee Mitigation For this mitigation option, a permittee provides funds to an in-lieu- fee sponsor, such as a public agency or non-profit organization (USACE 2008). Typically, the sponsor collects funds from multiple permittees to combine the financial resources necessary to build, maintain, and/or preserve the mitigation site. The in-lieu-fee sponsor is responsible for the success of the mitigation. In-lieu-fee mitigation occurs off-site, but unlike mitigation banking, it generally occurs after the permitted impacts have been incurred. In-lieu-fee mitigation is only an option when an agreement has previously been made between all the applicable regulatory agencies and the in-lieu-fee sponsor to provide mitigation. This agreement may include a list of projects for which the in-lieu-fee program will provide mitigation. Therefore, it may be necessary for a proposed project to be on the list to utilize this option. In-lieu-fee mitigation programs are often initiated in areas where mitigation bank credits are not available for public sale. 2008 Compensatory Wetland Mitigation Types • Restoration • Establishment/Creation • Enhancement • Preservation

50 Wetland Mitigation, Volume 2: A Guidebook for Airports 4.4 Wetland Mitigation Methods Many methods are used to generate mitigation credits. Any of these methods can be used with any of the mitigation options mentioned previously. The various methods are as follows: 4.4.1 Restoration Restoration is the re-establishment or rehabilitation of a wetland or other aquatic resource with the goal of restoring natural or historic wetland functions. Restoration may result in a gain in wetland function, wetland acres, or both (USEPA 2008). 4.4.2 Creation Creation involves constructing a wetland or other aquatic resource where a wetland did not previously exist (USEPA 2008). This typically involves the excavation, grading, and planting of the site to match the desired wetland type. Successful establishment results in a net gain in wetland acres and functions. 4.4.3 Enhancement Enhancement includes activities conducted within existing wetlands that heighten, intensify, or improve one or more wetland functions (USEPA 2008). Enhancement is often undertaken for a specific purpose such as to improve water quality, floodwater retention, or wildlife habitat value. A common and cost-effective form of enhancement is hydrological improvement. An example would be blocking downstream ditches to allow water to remain on the site longer. Enhancement results in increases in wetland function but does not result in a net gain in wetland acres. Enhance- ment is often a lower cost, risk, and time lag than other mitigation methods. Therefore, mitigation banks are often sited so that large tracts of degraded wetlands can be enhanced to generate credits. 4.4.4 Preservation Preservation consists of the permanent protection of ecologically important wetlands or other aquatic resources through the implementation of appropriate legal and physical mecha- nisms (i.e., conservation easements, title transfers). Preservation may also include protection of upland areas adjacent to wetlands as necessary to ensure protection or enhancement of the aquatic ecosystem. Preservation does not result in net gain of wetland acres and may only be used in certain circumstances, including when resources to be preserved contribute signifi- cantly to the ecological sustainability of the watershed (USEPA 2008). Wetland preservation is usually required as part of any mitigation plan. However, simply preserving a wetland (without enhancement, creation, etc.) is usually not considered sufficient to completely offset impacts. 4.5 Mitigation Credit Generation Mitigation credits are calculated in the same way that wetland impact debits are calculated. Tables 4-2 and 4-3 illustrate examples of mitigation credit generation through wetland creation and enhancement. The amount of credit generated varies with the mitigation method selected. Wetland creation often generates the most credit per acre because wetlands are being constructed in uplands. Therefore, all starting sub-scores in WRAP are zero. Other mitigation methods gener- ate less credit per acre because they start with an existing wetland and sub-scores that are greater than zero. Time lag and risk factors must also be incorporated into the table for an actual credit calculation; however, those factors are more advanced mitigation concepts and have been elimi- nated for simplicity in the tables below. It is important to note that time lag and risk will lower

Mitigation Types 51 the amount of credit generated. Note that assessment methodologies are constantly changing and evolving to be more accurate, efficient, and user friendly. WRAP is only one example of a func- tional assessment method. As previously stated above, the goal of any assessment method is to quantify the value of the wetland and assign a cost/currency to mitigating the loss of that wetland. Table 4-3 illustrates that a smaller amount of credit is earned if enhancements are made to an existing moderate quality wetland. For example, if the canopy is enhanced by planting appropriate native species and hydrology is improved by blocking a downstream ditch to reduce drainage, then the canopy and hydrology sub-scores will increase. These enhancements will also improve habitat for wildlife, so the wildlife utilization sub-score increases as well. As demonstrated above, wetland creation typically generates significantly more mitigation credit per acre than wetland enhancement. However, wetland creation is also typically more expensive, time-consuming, and riskier than other mitigation methods. 4.6 Summary When a project or activity impacts a wetland, those impacts must be mitigated. First, the type of wetland and extent of impacts must be determined. Then, the functions and values provided by that wetland must be quantified through the performance of a functional assessment. The methodologies for this assessment vary across regions. Once the amount and quality of wetland impacts are quantified, there are several options for mitigation. Permittee-responsible mitigation, purchasing credits in a mitigation bank, and in-lieu-fee mitigation are the most common options. Mitigation methods are chosen project by project. Besides the need to replace the lost functions and values of the impacted wetland, feasibility and cost of mitigation is also consid- ered. Options and methods for mitigation need to be decided before impacts take place. WRAP Parameters Before After Credit Wildlife Utilization 0 2 Canopy 0 2 Ground cover 0 2 Adjacent Buffer 0 2 Hydrology 0 2 Water Quality & Treatment 0 2 Score (Sum/18) 0.00 0.67 Wetland Size (Acres) 2.0 2.0 Functional Value (Score x Acreage) 0.00 1.34 +1.34 Source: This research team sample analysis is based on the South Florida Water Management District WRAP. Table 4-2. WRAP analysis for the creation of a moderate quality, two-acre forested wetland in an upland. WRAP Parameters Before After Credit Wildlife Utilization 2 2.5 Canopy 2 2.5 Ground cover 2 2 Adjacent Buffer 2 2 Hydrology 2 2.5 Water Quality & Treatment 2 2 Score (Sum/18) 0.67 0.75 Wetland Size (Acres) 2 2 Functional Value (Score x Acreage) 1.34 1.50 +0.16 Source: This research team sample analysis is based on South Florida Water Management District WRAP. Table 4-3. WRAP analysis for the enhancement of a moderate quality, two-acre forested wetland to a higher quality wetland.