Balancing Airport Stormwater and Bird Hazard Management (2015)

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12 C H A P T E R 3 Conclusions Drawing on the research tasks (described in Appendix A) and associated findings presented in Chapter 2, the research team has developed a single tool that allows for the man- agement of bird strike risk associated with the attraction of water-dependent birds to stormwater management BMPs at airports. The tool allows users to assess initial risk given spe- cies and stormwater design data, reduce that risk by incorpo- rating initial (i.e., current) wildlife mitigations, and further manage bird strike risk through the selection of BMP design alternatives and additional wildlife mitigation measures. Finally, the tool allows users to evaluate BMP alternatives for other factors beyond bird strike risk, depending on airport- specific priorities. The content and format of the Bird Strike Risk Analysis and Stormwater Management Decision Tool, as shaped by the research findings, are described in further detail in the sections below. Bird Strike Risk Analysis and Stormwater Management Decision Tool Tool Design The Bird Strike Risk Analysis and Stormwater Management Decision Tool is designed in Microsoft Excel 2010 to allow users to enter information (e.g., FAA strike data, stormwater design criteria, etc.), into Excel. Tool users are not expected to see or modify the software, but they must possess Excel 2010 or newer to use the application. The tool is designed on vari- ous tabs in the Excel spreadsheet. The research team designed the tool so that the user enters different categories of data (bird data vs. stormwater BMP data) on different tabs for clarity. This serves to simplify the inputs and help users understand the flow of the tool. The risk analysis portion of the tool is provided as a step-wise process (five steps in total), followed by a risk summary page. The risk calculations are contained on separate tabs and these tabs are hidden, so as not to confuse the user. The tool con- tent is summarized here and detailed further in the following subsections: • START: This sheet serves as a main menu with instructions and hyperlinks to all of the tool features. • Tool Overview: This sheet provides guidance on tool objectives and disclaimers. • Bird Strike Risk Analysis: The following sheets each summarize a step in the risk analysis. – Step 1: Identify Bird Species, History of Strikes, and Operations Data – Step 2: Identify Existing Bird Mitigations – Step 3: Define Initial BMP Characteristics – Step 4: Review Initial Risk and Identify Additional Bird Mitigations – Step 5: Develop Proposed BMP Options and Review Residual Risk • Bird Strike Risk Summary: This sheet summarizes the initial risk associated with the data in Steps 1–3, and the reduced risk associated with Steps 4 and 5 of the risk analysis. • BMP Alternatives Analysis: This tab allows the comparison of BMPs based on other BMP selection criteria. • Risk Matrix: Illustrates the SMS framework that formed the basis for tool calculations. • Additional Resources: Includes lists of the water-dependent bird species, mitigation options, recommended vegetation, definitions, references, and assumptions for informational purposes. Each tab includes “hot buttons” to allow users to go from one step to the next, access relevant additional resources, and go back to the main menu to facilitate navigating through the tool. Each tab also includes an overview of the specific step, instructions for completing the assessment, important definitions, and notes, along with the data entry and risk results. Conclusions and Suggested Research

13 Risk Matrix The “Risk Matrix” tab depicts the risk matrix, based on the SMS framework, which forms the basis for assigning scores to severity and likelihood factors and calculating overall risk. This tab is provided for informational purposes to illustrate how the banding of each risk factor corresponds to the sever- ity or probability levels. The research team included this tab at the back of this tool to allow users to first gain an understand- ing of various risk analysis inputs on previous tabs before seeing how these inputs are integrated within the matrix. Risk is defined as the combination of the severity (potential for mass) and the likelihood that the bird will be attracted. The result of this combination is a risk rating. The risk matrix establishes the definitions and parameters for severity and likelihood used in the tool and serves as the foundation for all subsequent steps. The concept of risk (Likelihood × Severity) allows us to independently evaluate each of these risk factors. Within each risk factor, there are multiple potential hazards that exhibit a variety of risk levels. All risk factors and their corresponding levels are outlined in the risk matrix and this forms the basis of the remaining risk assessment. The levels for all factors cor- respond to numerical values. These values are then combined to result in an overall risk, incorporating both severity and likelihood. By addressing risk factors, controls, and priority factors, the tool allows an airport to not only evaluate existing hazards independent of any additional efforts or controls, but provides a way to test the applicability of additional control efforts and truly measure potential risk reductions. Step 1 Input Bird Observation and Strike Data Step 1 includes four input tables whereby the user selects the species of concern and enters species-specific bird obser- vation and strike data, identifies confidence in the bird data, tallies total strikes for water-dependent birds, and inputs air- port operations. In the Bird Observation Data table, the user selects the water-dependent bird species of concern from the dropdown list of options, and the tool automatically popu- lates the relative hazard score associated with each species. Then, the user must select the frequency of observations, proximity of observations to aircraft movement areas, and the number of strikes reported for each species of concern selected. The Bird Data Confidence table allows the user to adjust the influence that species likelihood factors have on the overall risk equation if they have particularly low confidence in airport-specific bird strike or observations data. To simplify user input, the user will simply select “High” or “Low” confi- dence, and factors that are associated with “Low” confidence will have their weighting values reduced by one-half compared to default weighting values. Factors with “High” confidence will retain the non-adjusted default weighting values. If the user has equal confidence in the quality of strike data, history (fre- quency) of observations, and proximity of bird sightings, they may select equal weighting for all three and keep the default weighting as originally designed. This approach simplifies a difficult concept for users to understand and allows the overall risk to be tailored to airport-specific data quality. In the Total Bird Strikes table, the user identifies if there is strike data for water-dependent bird species that were not identified as a species of concern, and then enters the total number of strikes for other water-dependent birds not already included. In the airport operations table, the user must enter the number of operations at the airport for the same time period used to assess the number of strikes reported. Once the strike and operations data are entered, the tool calculates the percentage of total airport bird strikes associated with each species of concern and the strike rate per airport operation compared to the national average. The research team decided to expand the original tool design to allow for 10 species inputs based on feedback from the panel. This will allow a user to evaluate up to 10 different bird species of concern at a time, select different options for each risk factor for the same species, or choose up to 10 differ- ent mitigation options for the same species at once. In other words, if the user is not selecting 10 total species for analysis, the user can assess the same species with varying inputs. If the user is not confident in their assessment of their bird strike data or bird observations, the 10 available rows allow the user to compare the risk for a single species based on several esti- mates for frequency of observations and/or strikes. The user can then decide to manage for the “riskiest” result or not. Step 2 Identify Existing Bird Mitigations In Step 2, the user must select (from a drop-down menu) the current bird mitigations implemented at their airport. Miti- gations can be selected for each species and each of the SMS Hierarchy of Controls categories as outlined in Table 2-3: engi- neering, warnings, and administrative. For each mitigation, the user must input the frequency with which the particular miti- gation is implemented: upon bird sighting or ongoing. This step is for identifying existing bird mitigations only. Step 3 Define Initial Stormwater BMP Characteristics The next step in the risk assessment involves defining the initial BMP characteristics. As previously discussed, the user will define various BMP design elements instead of selecting a size and type of BMP. The tool allows the user to evaluate an existing or planned BMP. At this step, the user must select

14 (from a drop-down menu) design characteristics in the fol- lowing categories: water exposure, BMP geometry, BMP loca- tion, and BMP vegetation. Based on the user inputs, the tool automatically calculates the banding level assigned to each selection (e.g., Levels 1 through 5). Additional BMP charac- teristics are presented as yes/no questions representing prior- ity impact factors. Step 4 Additional Mitigations Once the bird observation and strike data has been entered and the BMP characteristics defined, the user will have the opportunity to review the initial risk and the risk reduction associated with existing mitigation measures entered in Step 2. The left side of the table illustrates the initial risk associated with species selection, airport bird observations, strike data, and the initial BMP design characteristics, both with and without the existing mitigations. This presentation of the risk both with and without the existing mitigations allows users to see the impact and results of existing mitigation practices. At this step, the user can input additional bird mitigations, if desired, to further reduce the risk of a bird strike. Entering the mitigations at this step is identical to entering the mitiga- tions in Step 2. The tool then automatically totals the existing and proposed mitigations and reduces risk based on imple- mentation of zero, one, or more than one measure in each category. There is no additional risk reduction for two (2) or more mitigations in each category. Step 5 Reduce Risk Through Proposed Stormwater BMP Modifications The research team recognized the benefit of being able to compare several BMP design options simultaneously and added the ability to compare up to three BMP design modifica- tions in Step 5 to explore the effect of BMP characteristics on bird strike risk. The initial BMP characteristics (from Step 3) are displayed on this tab to allow the user to review the origi- nal BMP design while selecting design characteristics for the alternative options. This is useful for making decisions about design modifications to be examined. At the bottom of the worksheet, the existing risk for each species (including the existing BMP design and existing mitigations) is presented from the previous step, along with the proposed risk associated with each BMP design modification. This facilitates review of the impact of each design modification on bird strike risk. BMP Alternatives Analysis The BMP alternatives analysis allows the user to review the risk analysis results for each BMP alternative in context with other non-bird strike factors that typically affect airport BMP selection and design decision making. This tab is not a part of the risk analysis, but does incorporate results for a selected species from the risk analysis as one of many fac- tors affecting BMP selection. For example, an underground detention facility might be most effective at reducing bird strike risk, but these types of BMPs tend to be less cost- effective than other options, which may reduce their prac- ticality depending on available funding and airport-specific priorities. Users are asked to define the importance of vari- ous criteria to BMP selection, define objectives for these cri- teria, and then evaluate each of the BMP alternatives for how well it meets the user-defined objectives. The results of the risk analysis and BMP evaluations are then combined and scored to allow users to see how well each BMP alternative meets user-defined objectives. As such, this tab serves as a tool for the comparison and selection of stormwater BMP alternatives. Additional Information Provided in the Tool In addition to the matrix and tool steps, several other tabs are included to provide the user with additional information and clarify the process. The START tab provides a summary of the steps involved with implementing the tool and includes hot button links to navigate to each of the steps that are included on separate tabs. The Overview tab provides back- ground information that may help the user to understand tool assumptions and caveats for use of the tool. This infor- mation does not feed into the risk analysis, but is provided solely for the benefit of documenting the tool assumptions and features for the user. The tool will also include the following tabs for additional information and guidance: • Species tab listing all of the species initially considered for inclusion in the tool (including those not attracted by stormwater); • Mitigations tab defining all of the mitigation measures and providing examples of each; • USDA tab defining the vegetation on the USDA list; • Definitions; and • References and assumptions. Tool Features During the case studies, the research team identified the need to clarify stormwater and bird strike terminology and user inputs in the tool. The research team decided to add some additional clarification to the tool to increase understanding

15 of the stormwater and bird attractant concepts. The research team developed the following features in the tool: • Clarifying instructions for selection of inputs from drop- down lists; • Additional “pop up” instructions that appear when user hovers the mouse over a risk factor; • Guidance explaining how different BMP design character- istics affect bird strike risk; • Color-coding of data entry cells in Excel to indicate user- defined inputs, default values, and other information; • Color-coding of the risk analysis steps; • Calculation of BMP perimeter irregularity in the tool; • Enhancement of the user interface to facilitate ease of use; and • Reorganization of the START tab and steps of the tool to facilitate navigation. Suggested Research The research team has found that more research is needed to accurately quantify bird strike risk. As an industry, there is an accepted understanding that water on an airfield is a hazardous wildlife attractant. Additionally, there is some research that quantifies the parameters of this attractant, but more information is needed. Specifically, the industry would benefit from a greater understanding of stormwater BMP location in relation to the airport movement areas. It would be beneficial to quantify a distance from movement areas where risk of a strike becomes minimal or “acceptable,” within the AOA. Airports rarely have a mechanism for regu- lating stormwater BMPs off of their properties. Also, it would be beneficial to know the effect on risk when manipulating the placement, not just distance, of stormwater BMPs on or around the AOA. For example, is it more or less risky to con- struct all ponds on one side of the movement areas, poten- tially reducing the number of birds crossing over? Or, would it be best to create ponds as far apart from one another as possible to create an isolation affect? These are questions that warrant further investigation, perhaps both on stormwater BMP placement and patterns in wildlife movements. As previously addressed, this ACRP project focuses on the relationship between man-made stormwater BMPs and poten- tially hazardous water-dependent bird species to decrease the risk of a bird strike. The research needs to be expanded to include all hazardous birds, terrestrial vertebrates (or potentially hazardous wildlife), and more habitat types. More research is needed on the synergistic effects of numerous desirable habi- tat types located on or around airports. For example, how does placing a stormwater BMP between agricultural fields and an airport affect risk? In regards to quantifying the hazards of all wildlife, there are several published lists containing rela- tive hazard scores for species involved in aircraft strikes. For the purposes of this ACRP project, the research team has utilized the list published by DeVault et al. (2011), which combines mammals and birds, comparing their risks to each other. There are other published rankings, with different rela- tive hazard scores, that separate birds and mammals (Dolbeer et al. 2013). As an industry there is a need for relative hazard scores, which are universally accepted, and clearly defined. The methodologies resulting in the universally accepted scores also must clearly define hazard and risk. Does hazard incor- porate both likelihood and severity, or should it be limited to severity only? Should the scores be based solely on wildlife biomass? If so, how do we quantify biomass for small species that commonly flock (e.g., European starlings)? In addition, there appears to be substantial research on the attractiveness of airport turf grasses to wildlife; however, there is a need for more research on the attractiveness of aquatic vegetation to hazardous wildlife. It would be beneficial to airfield managers and planners to have a generic list of aquatic vegetation that is least attractive to these water-dependent species. There is some research on the design parameters of storm- water BMPs that are attractive to wildlife, but some of the language is potentially confounding. For example, AC 150/5200- 33B recommends designing stormwater BMPs with a linear edge to decrease attractiveness, the WashDOT Manual recom- mends a length-to-width ratio of the BMP of 3:1 or greater to decrease attractiveness (WashDOT 2008), and research from Blackwell et al. (2008) and Fox et al. (2013) suggests that an increased perimeter irregularity (when compared to a perfect circle) leads to an increase in bird attractiveness. These sources are somewhat contradictory by implying a long, narrow, linear BMP is least attractive (WashDOT 2008) and also suggesting a BMP designed like a perfect circle is least attractive (Blackwell et al. 2008; Fox et al. 2013). The research team believes that perhaps one set of design criteria (long and linear) refers to reduced surface area whereas the Blackwell et al. (2008) defini- tion of perimeter irregularity refers to the amount of available shoreline. Both increased surface area and increased shoreline are proven attractive characteristics in BMP design (Fox et al. 2013). However, these parameters need to be further investi- gated and specific recommendations should be made to deter- mine which design is actually preferable from a wildlife hazard management perspective. Finally, it would be most beneficial to eliminate the attrac- tant all together. More research is needed to either develop alternative methods for mitigating stormwater for water qual- ity purposes, etc., or to reduce the costs of existing systems that completely enclose the stored water. Some airports are converting to stormwater master plans that only include “over- land flow” as the method of discharging stormwater, rather

16 than proposing water storage. For example, North Carolina state legislature passed Senate Bill 229 in 2011, amending certain environmental and natural resource laws. Section 6 specifically directs the state Department of Environment and Natural Resources to accept alternative measures of stormwater control at public airports in accordance with AC 150/5200-33B. Per Section 6 of the bill, “the Department shall not require the use of stormwater retention ponds, stormwa- ter detention ponds, or any other stormwater control mea- sure that promotes standing water . . . at public airports . . . [or at any] development projects located within five statute miles from . . . an air operations area. . . .” The guidance con- tinues, “The Department shall deem runways, taxiways, and any other areas that provide for overland stormwater flow that promote infiltration and treatment of stormwater into grassed buffers, shoulders, and grass swales permitted pursu- ant to the state post-construction stormwater requirements.” These methods eliminate the attractant from airfields com- pletely and make strides toward reducing overall wildlife strike risk.