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Interpreting the Results of Airport Water Monitoring (2017)

Chapter: Chapter 3 - Applying and Responding to Monitoring Data

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Suggested Citation:"Chapter 3 - Applying and Responding to Monitoring Data." National Academies of Sciences, Engineering, and Medicine. 2017. Interpreting the Results of Airport Water Monitoring. Washington, DC: The National Academies Press. doi: 10.17226/24752.
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Suggested Citation:"Chapter 3 - Applying and Responding to Monitoring Data." National Academies of Sciences, Engineering, and Medicine. 2017. Interpreting the Results of Airport Water Monitoring. Washington, DC: The National Academies Press. doi: 10.17226/24752.
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Suggested Citation:"Chapter 3 - Applying and Responding to Monitoring Data." National Academies of Sciences, Engineering, and Medicine. 2017. Interpreting the Results of Airport Water Monitoring. Washington, DC: The National Academies Press. doi: 10.17226/24752.
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Suggested Citation:"Chapter 3 - Applying and Responding to Monitoring Data." National Academies of Sciences, Engineering, and Medicine. 2017. Interpreting the Results of Airport Water Monitoring. Washington, DC: The National Academies Press. doi: 10.17226/24752.
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Suggested Citation:"Chapter 3 - Applying and Responding to Monitoring Data." National Academies of Sciences, Engineering, and Medicine. 2017. Interpreting the Results of Airport Water Monitoring. Washington, DC: The National Academies Press. doi: 10.17226/24752.
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Suggested Citation:"Chapter 3 - Applying and Responding to Monitoring Data." National Academies of Sciences, Engineering, and Medicine. 2017. Interpreting the Results of Airport Water Monitoring. Washington, DC: The National Academies Press. doi: 10.17226/24752.
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Suggested Citation:"Chapter 3 - Applying and Responding to Monitoring Data." National Academies of Sciences, Engineering, and Medicine. 2017. Interpreting the Results of Airport Water Monitoring. Washington, DC: The National Academies Press. doi: 10.17226/24752.
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Suggested Citation:"Chapter 3 - Applying and Responding to Monitoring Data." National Academies of Sciences, Engineering, and Medicine. 2017. Interpreting the Results of Airport Water Monitoring. Washington, DC: The National Academies Press. doi: 10.17226/24752.
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Suggested Citation:"Chapter 3 - Applying and Responding to Monitoring Data." National Academies of Sciences, Engineering, and Medicine. 2017. Interpreting the Results of Airport Water Monitoring. Washington, DC: The National Academies Press. doi: 10.17226/24752.
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Suggested Citation:"Chapter 3 - Applying and Responding to Monitoring Data." National Academies of Sciences, Engineering, and Medicine. 2017. Interpreting the Results of Airport Water Monitoring. Washington, DC: The National Academies Press. doi: 10.17226/24752.
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Suggested Citation:"Chapter 3 - Applying and Responding to Monitoring Data." National Academies of Sciences, Engineering, and Medicine. 2017. Interpreting the Results of Airport Water Monitoring. Washington, DC: The National Academies Press. doi: 10.17226/24752.
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Suggested Citation:"Chapter 3 - Applying and Responding to Monitoring Data." National Academies of Sciences, Engineering, and Medicine. 2017. Interpreting the Results of Airport Water Monitoring. Washington, DC: The National Academies Press. doi: 10.17226/24752.
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Suggested Citation:"Chapter 3 - Applying and Responding to Monitoring Data." National Academies of Sciences, Engineering, and Medicine. 2017. Interpreting the Results of Airport Water Monitoring. Washington, DC: The National Academies Press. doi: 10.17226/24752.
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Suggested Citation:"Chapter 3 - Applying and Responding to Monitoring Data." National Academies of Sciences, Engineering, and Medicine. 2017. Interpreting the Results of Airport Water Monitoring. Washington, DC: The National Academies Press. doi: 10.17226/24752.
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Suggested Citation:"Chapter 3 - Applying and Responding to Monitoring Data." National Academies of Sciences, Engineering, and Medicine. 2017. Interpreting the Results of Airport Water Monitoring. Washington, DC: The National Academies Press. doi: 10.17226/24752.
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Suggested Citation:"Chapter 3 - Applying and Responding to Monitoring Data." National Academies of Sciences, Engineering, and Medicine. 2017. Interpreting the Results of Airport Water Monitoring. Washington, DC: The National Academies Press. doi: 10.17226/24752.
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Suggested Citation:"Chapter 3 - Applying and Responding to Monitoring Data." National Academies of Sciences, Engineering, and Medicine. 2017. Interpreting the Results of Airport Water Monitoring. Washington, DC: The National Academies Press. doi: 10.17226/24752.
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Suggested Citation:"Chapter 3 - Applying and Responding to Monitoring Data." National Academies of Sciences, Engineering, and Medicine. 2017. Interpreting the Results of Airport Water Monitoring. Washington, DC: The National Academies Press. doi: 10.17226/24752.
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Suggested Citation:"Chapter 3 - Applying and Responding to Monitoring Data." National Academies of Sciences, Engineering, and Medicine. 2017. Interpreting the Results of Airport Water Monitoring. Washington, DC: The National Academies Press. doi: 10.17226/24752.
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Suggested Citation:"Chapter 3 - Applying and Responding to Monitoring Data." National Academies of Sciences, Engineering, and Medicine. 2017. Interpreting the Results of Airport Water Monitoring. Washington, DC: The National Academies Press. doi: 10.17226/24752.
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Suggested Citation:"Chapter 3 - Applying and Responding to Monitoring Data." National Academies of Sciences, Engineering, and Medicine. 2017. Interpreting the Results of Airport Water Monitoring. Washington, DC: The National Academies Press. doi: 10.17226/24752.
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Suggested Citation:"Chapter 3 - Applying and Responding to Monitoring Data." National Academies of Sciences, Engineering, and Medicine. 2017. Interpreting the Results of Airport Water Monitoring. Washington, DC: The National Academies Press. doi: 10.17226/24752.
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Suggested Citation:"Chapter 3 - Applying and Responding to Monitoring Data." National Academies of Sciences, Engineering, and Medicine. 2017. Interpreting the Results of Airport Water Monitoring. Washington, DC: The National Academies Press. doi: 10.17226/24752.
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97 C h a p t e r 3 3.1 Introduction This chapter addresses the application of water monitoring data. Application of monitor- ing data is defined in this guidebook as the use of sufficiently vetted and statistically inter- preted water monitoring data to support the airport’s decision-making processes. For the information in this chapter to be used effectively, airport staff should first use processes similar to those presented in Chapters 1 and 2 to quantitatively describe a representative and accurate data set. Airport staff may apply water monitoring data in a variety of functions, as illustrated in Figure 21. The objective of this chapter is to provide guidance to airport staff for several commonly encountered water monitoring applications. The approach to applying water monitoring data is influenced by whether the decisions are being made on past events (e.g., responding to non- compliance situations that have already occurred), current conditions (e.g., responding to an ongoing compliance condition or using monitoring data to support operational decisions), or future applications (e.g., establishing conditions in the next permit iteration). Figure 22 lists the key concepts in the chapter. In the electronic version of this document, hyperlinks to the referenced sections are provided. Key terms used in this chapter are provided in Section 3.2. 3.2 Terminology Critical to Applying and Responding to Monitoring Data A variety of terms are used in reference to stormwater monitoring data application at airports. Although many of these terms are used interchangeably by airport staff and consultants, they are uniquely defined in this guidebook to facilitate a consistent understanding of the detailed concepts presented herein. Key terms that are critical to the understanding of the content in this chapter are defined in this section for user reference. Additionally, the glossary provides defini- tions for a variety of other terms that are relevant to overall guidebook content. Applying and Responding to Monitoring Data Past Applications Response to issues identified in acquired data Present Applications Use of data to support real- time actions Future Applications Use of data to support future activities Figure 21. Aspects of applying water monitoring data.

98 Interpreting the results of airport Water Monitoring Best Management Practice – A term that sometimes encompasses mechanisms for the ongoing control and treatment of stormwater runoff. The 2015 MSGP uses the term “control measures” to refer to BMPs. Many regulators are replacing the term “BMP” with “control measure.” The term “BMP” is not typically associated with stormwater treatment systems intended for specific pollutants such as deicer treatment systems. Metadata – Information that describes the contents and context of the data. Root cause analysis – A process to identify and evaluate the fundamental cause of an undesir- able condition or issue. SCADA – Supervisory control and data acquisition system, which is used in online computer- based management of stormwater controls to process data inputs from monitoring instruments, provide feedback to system equipment, and provide graphic data to system operators. SWPPP or SWPCP – Stormwater pollution prevention plan, alternatively referenced as stormwater pollution control plan in some areas. Required to be developed as part of NPDES permit compliance. Often details potential pollutant sources in specific airport drainage areas. TMDL – Total maximum daily load, a regulatory mechanism for allocating pollutant loadings to individual discharges in a watershed to address impairments to a receiving stream that prevent the water body from meeting its designated uses. Figure 22. Key concepts for the application of water monitoring data. 3.4 Application 2: Using Data in • 3.4.1 Developing Permit Conditions • 3.4.2 Discussing Monitoring Frequency with Regulators • 3.4.3 Proposing Alternate Monitoring Parameters and Methods • 3.4.4 Proposing Alternate Monitoring Locations 3.6 Application 4: Stakeholder Communication • 3.6.1 Conducting Effective Outreach • 3.6.2 Handling Non-compliance Incidents Regulatory Compliance Issues 3.3 Application 1: Responding to Establishing Permit Conditions and Public Outreach • 3.3.1 Define the Issue • 3.3.2 Review Related Existing Information to Further Understand • 3.3.3 Communicate and Coordinate with the Regulator • 3.3.4 Conduct Source and Root Cause Investigations • 3.3.5 Collect Additional Data to Confirm Compliance the Compliance Issue 3.5 Application 3: Applying Monitoring Data • 3.5.1 Planning and Design • 3.5.2 Management of Ongoing Operations and Maintenance Activities • 3.5.3 Tracking and Improving Environmental Performance Airport Stormwater Quality to Support Operations and Improve

applying and responding to Monitoring Data 99 3.3 Application 1: Responding to Regulatory Compliance Issues Regulatory compliance issues are associated with situations where monitoring data indicate that a permit condition has been, or has significant potential to be, violated. When water-related compliance issues first appear, they can be challenging for airports because: • Issues often appear without warning. • It may not be clear if the issue is real. • The extent of the issue (how widespread the problem is) is unknown. • The length of time the issue has been occurring is unknown. • The length of time the issue may continue is unknown. • The applicable regulations and permit conditions may not be readily understood. • The compliance implications (e.g., reporting responsibilities, notice of violation, consent orders, fines) are not clear. • The potential impacts to airport and other stakeholders have not been fully vetted. • The resources needed to be allocated for further investigation are not evident. Addressing a potential compliance issue often involves use of water monitoring data that has already been collected. New data may be needed to complete the picture. Understanding the risks and benefits of collecting additional water monitoring data is an important element in establishing a plan for compliance. When a potentially significant regulatory compliance issue is identified, there is often pressure to characterize the issue and identify options before the situation can be sufficiently understood and acted upon. Decisions made without understand- ing the cause and implications of a compliance issue can lead to unnecessary expenditures by the airport, inappropriate response activities, incomplete reporting, and, in some cases, unwar- ranted bad press. These problems often result in frustrated airport management, may hinder an effective working relationship with a regulator, and may affect stakeholder and public percep- tions unnecessarily. Clearly defining the issue, reviewing related existing data, determining if additional data is necessary, and proactively coordinating with the regulator can lead to more desirable outcomes. The following sections provide step-wise guidance on considerations for use of water moni- toring data in addressing water-related compliance issues. 3.3.1 Define the Issue The first step in responding to a regulatory compliance issue is to fully define the issue. Defining the issue supports identification of appropriate evaluation techniques and informs additional data collection needs. The Topical Tips box presents common questions pertinent to defining a compliance issue. Airport staff should catalogue answers to these questions; develop a list of known and unknown information; and seek input from monitoring staff, operators, maintenance personnel, and other stakeholders that may have knowledge of the situation. The identified unknowns can help set the plan for the subsequent investigation. Define the Issue Review Related Existing Data Coordinate with the Regulator Conduct Source and Root Cause Investigations Collect Additional Data to Confirm Compliance Define the Issue Review Related Existing Data Coordinate with the Regulator Conduct Source and Root Cause Investigations Collect Additional Data to Confirm Compliance

100 Interpreting the results of airport Water Monitoring Review the Data A review of water monitoring data should follow, wherein the extent, accuracy, and represen- tativeness of the data is initially characterized. The objectives of the review are as follows: • To identify data that can be explicitly verified (e.g., review field observation sheets, chain-of- custody forms, QA/QC documents, etc.). • To identify data that is determined to be sound. • To characterize uncertainties in data accuracy. • To assess whether sufficient data exists to draw conclusions. More often than not, there is not enough available data to completely define the compliance issue. • To define limitations of the data set, such as the conditions during which the data was collected. • If the compliance issue is an exceedance based on laboratory analysis, to review the laboratory report and determine if there are any flags or dilution issues associated with the data. • If the compliance issue is identified in data collected by airport personnel, to confirm calibration and maintenance records for the monitoring equipment. If the instrument calibration is suspect, the instruments should be recalibrated and additional measure- ments taken. If data is suspected to be inaccurate or non-representative of the stormwater discharge, that information should be conveyed to the regulator when the compliance issue is reported. Review the Regulatory Requirements It is also helpful to review the regulatory requirements relative to water monitoring. Under- standing applicable regulatory requirements enables proper reporting, facilitates greater under- standing of the potential water quality impacts associated with the compliance issue, and influences decision-making regarding next steps. Consider the questions in the following Topical Tips box. For more information about verifying data, see: 2.3 Verifying the Accuracy and Representativeness of Raw Data Topical Tips Questions to Ask When Defining a Compliance Issue • What locations are affected? • Does the issue involve measured parameters, observed conditions, or both? • How many parameters measured were out of compliance? • How far out of compliance is the stormwater discharge, and how significant does the compliance issue appear to be? • When did the compliance issue occur? How many instances? Is this a recurring condition or something new? • Is there a trend in the data or was this a sudden occurrence? • Is it possible the airport is still out of compliance now? • What parties are or may be affected? Is it confined to the airport or has the potentially non-compliant stormwater reached waters off of the property? • Who has been notified, and who needs to be notified? • Has the data been reviewed to verify it is accurate and representative of storm- water discharge conditions? • Is there an obvious cause or explanation (e.g., reported spill)?

applying and responding to Monitoring Data 101 Airports subject to the U.S. EPA MSGP are required, on the same day a condition requiring corrective action is found, to take all reasonable steps to minimize or prevent the discharge of pollutants until a permanent solution is installed and made operational. Permanent solutions must be installed before the next storm event if possible, and within 14 calendar days from the time of discovery of the corrective action condition. If it is infeasible to complete the cor- rective action within 14 calendar days, the permit holder must document why it is infeasible to complete the corrective action within the 14-day time frame. The permit holder must also identify the schedule for completing the work, which must be done as soon as practicable after the 14-day time frame but no longer than 45 days after discovery. If the completion of cor- rective action will exceed the 45-day time frame, the permit holder may take the minimum additional time necessary to complete the corrective action, provided that they notify the U.S. EPA Regional Office of the intention to exceed 45 days, the rationale for an extension, and a completion date, which must also be included in the corrective action documentation. Where corrective actions result in changes to any of the controls or procedures documented in the SWPPP, the SWPPP must be modified accordingly within 14 calendar days of completing correc- tive action work (U.S. EPA, 2015). Airports subject to state-issued general permits or individual permits should consult their specific permit language regarding the requirements when monitoring data indicates an exceed- ance of a benchmark or effluent limit. Ideally these responsibilities are summarized in the water monitoring plan so they are readily available for review when an issue arises. 3.3.2 Review Related Existing Information to Further Understand the Compliance Issue After the initially acquired data is documented, it is likely that a more detailed review of the existing data will be needed. It may also be necessary to gather additional information about unknown aspects of the issue. This may mean reviewing and correlating related data, or conducting additional statistical analysis of exist- ing data. Review of related data and statistical analysis may identify the cause of the issue, clarify the extent of the issue, or illustrate extenuating circumstances surrounding the issue. Topical Tips Questions to Ask When Evaluating Regulatory Requirements Associated with a Permit Compliance Issue • Was an effluent limit exceeded or was it a benchmark? • Was the limit an average, maximum, or minimum? • Was it an acute or chronic water quality criterion that was not met? • What is the relevant water quality standard? • Was it a narrative criterion that was not met? • Was a required monitoring event missed? • What are the reporting requirements for the compliance issue? • Are additional follow-up monitoring or response actions prescribed in the permit or regulation? Define the Issue Review Related Existing Data Coordinate with the Regulator Conduct Source and Root Cause Investigations Collect Additional Data to Confirm Compliance

102 Interpreting the results of airport Water Monitoring Metadata The numeric monitoring data should be supplemented with metadata. Metadata is a term for information describing the contents and context of data. Examples of potential metadata for a water monitoring compliance issue are provided in the Topical Tips box. If field data collection sheets like the example in Appendix A have been completed during sampling, they should be reviewed for relevant information. Topical Tips Types of Metadata to Potentially Evaluate with Compliance Issue • QA/QC data and reports from laboratories that could be used to identify any potential analysis errors • Chain-of-custody documentation • Field observations from the time of sample collection • Review of sample collection procedures associated with the event • Review of logged data from field sampling and analytical instruments • Analytical results from other parameters measured at the same location at the time the compliance issue was noted • Weather conditions for the time frame of the compliance issue • Field conditions and analytical data from other monitoring locations at the air- port during the time frame of the compliance issue • Field conditions, weather conditions, and analytical data from the monitoring location where the compliance issue was noted during the time frame just prior to the compliance issue • Field conditions, weather conditions, and analytical data from the monitoring location where the compliance issue was noted during the time frame following the compliance issue • Reports of spills, unusual operating conditions, maintenance issues, or failed control measures in the time frame leading up to the compliance issue Statistical Analysis While statistical analyses may have been conducted on the initially collected data set, addi- tional statistical analyses specific to the identified issue could be a powerful asset. For example: • The distribution of the data could be re-evaluated to determine if previously applied statistics used in assessment of compliance such as the mean were valid. • Box plots could be used to assess the spread of the data to help understand where the data points associated with non-compliance lie relative to the remainder of the data set. A non- compliance point that is a significant outlier (e.g., the non-compliance data point is below the 5th percentile or above the 95th percentile of the data set) may suggest an unusual cause for the value. • Related parameters could be plotted against each other to assess relationships. Two related parameters (e.g., BOD and COD) should have a tendency to correlate well in untreated storm- water. Two related parameters not correlating well in untreated stormwater may suggest an analytical error or unusual pollutant condition. • Trend analyses may assist with understanding the history leading up to a compliance issue. Although a compliance issue may be relatively recent, gradual increases in concentrations For more information about conducting statistical analy- sis of data, see: 2.4 Analyzing the Data

applying and responding to Monitoring Data 103 may have been occurring for some time prior to a non-compliance incident. Review of his- torical field condition observations and related parameters may also help identify when the circumstances leading to the compliance issue started. Understanding the timeline leading to a compliance issue can assist with identifying operational and maintenance activities that may have led to an increase in pollutants in the stormwater discharge. • A time series graph illustrating concentrations over time of several related parameters may help understand the context of the issue. For example, if the compliance issue was a dissolved oxygen reading that was below the minimum limit, a graph illustrating dissolved oxygen and other potentially related parameters like oil and grease, TOC, and propylene glycol over time may help identify if the issue is a result of a deicing activity pollutant or a maintenance/fueling activity pollutant. Scatter plots of concurrently analyzed parameters could also be used to identify potential correlation between them. Getting some perspective on whether the non-compliance data is within a normally expected range or trend as opposed to being an outlier or isolated incident is a key outcome at this stage of the non-compliance assessment. 3.3.3 Communicate and Coordinate with the Regulator Once the issue has been defined and related existing data has been reviewed, the airport must determine when to coordinate with the regulator. Coordination could include the initial report- ing of the issue, coordination on response actions, reporting of additional data collected and status of response, and responding to requests for additional information. In some situations, if imme- diate reporting is not required, an airport may choose to collect additional monitoring data or initiate a root cause analysis before coordinating with the regulator (e.g., if the exceedance occurs mid-month prior to required submittal dates for the Discharge Monitoring Report). Report the Compliance Issue to the Regulator While reporting requirements for compliance issues are typically prescribed in a permit or regulation, it may be in the airport’s best interest to provide the regulator with additional information that is not required by permit or regulation when reporting a compliance issue. Consider additional information that is available from a review of related existing data that may help a regulator better understand the situation. If a regulator is well informed about a compli- ance issue, it allows them to tailor their response more appropriately to the specific situation. Without adequate supporting information, a regulator may be forced to assume the worst-case scenario of a compliance incident and may either request extensive additional information to better understand the situation or require the airport to take action based on the limited data provided. Most importantly, if airport personnel have reason to believe that the data collected may not be accurate or representative of the stormwater discharge, they should report that the data may not be valid, and information supporting that assertion should be submitted to the regulator. If equipment was recalibrated, or different equipment was used and subsequent measurements conducted during the same event yielded compliant results, that data should be presented. If monitoring was conducted from stagnant flow that was not discharging, or when backflow from the receiving water is suspected, this information should be communicated to the regulator as well. If the analytical report from the laboratory indicated a dilution issue, or other flag, that information should be included in the report. When making a report of a compliance issue to a regula- tor, consider providing addi- tional information to help the regulator better under- stand the situation. Define the Issue Review Related Existing Data Coordinate with the Regulator Conduct Source and Root Cause Investigations Collect Additional Data to Confirm Compliance

104 Interpreting the results of airport Water Monitoring If the airport has already determined the likely cause of the issue, consider describing in detail the likely cause in the report to the regulator. If the airport has already taken steps to address the issue, or if steps are already planned to address the issue, these actions should also be described to the regulator. Providing information about actions already taken, or commitments already made by the airport to address the compliance issue will allow the regulator to consider the air- port’s actions to remedy the issue in its response. If the airport has reason to believe that the compliance issue is an isolated incident that is unlikely to occur again, consider providing information that supports that assertion. Information support- ing an assertion that the data is an isolated incident and unlikely to reoccur could include statistical information that indicates that the compliance issue is an outlier, a historical spill log indicating an isolated and unusual spill incident, or metadata describing unusual weather conditions. Finally, consider including in the report of non-compliance any information that the reg- ulator might need to better understand the situation. This could include field conditions noted or photographed, graphs illustrating correlation between various parameters or weather events, statistical analysis of the parameter out of compliance or related parameters, a timeline describing events leading up to the compliance issue, and receiving stream data from the same period that describes water quality at the time of the compliance issue. Consider what type of information a regulator might need to make a decision about how to respond or react to the compliance issue. A proactive approach to coordination with a regulator may include discussions about planned response activities. Discussing planned response activities with the regulator would allow the air- port to describe to the regulator what the airport feels is the best response plan given the nature of the compliance issue and to receive input and buy-in from the regulator prior to implement- ing response actions. This could avoid time and money wasted on response actions that may ultimately be deemed by the regulator as insufficient or inappropriate. When planned actions are discussed with the regulator, expectations must be clearly defined for the time frame for making improvements, particularly capital improvements, and for the schedule for any future interactions with the regulator, including submittal of additional data, reports, or follow-up meetings. 3.3.4 Conduct Source and Root Cause Investigations When a compliance issue is identified, the airport may decide to undertake a source investigation potentially supported with a root cause analysis. The purpose of a source investigation is to identify the activities, conditions, timing, and locations that may have contributed or are still contributing to a change in monitored water quality. Such investigations are typically triggered by the following circumstances: 1. When monitoring data is acquired and analyzed, it is often compared to a limiting value, such as a numeric discharge permit limit, permit benchmark, or performance standard as part of the statistical analysis process described in Chapter 2. Data that exceeds, or is trend- ing toward, the limiting value often signifies a change in the conditions that affect pollutant concentrations or flow. 2. Field observations are made (e.g., presence of odors, colors, sheen, biofilm, solids, foam) that imply a change in conditions in the drainage area upstream of the stormwater discharge. 3. Water monitoring data reveals the presence of a pollutant that was not previously detected. For more information about determining the cause of a compliance issue, see: 3.3.4 Conduct Source and Root Cause Investigations Define the Issue Review Related Existing Data Coordinate with the Regulator Conduct Source and Root Cause Investigations Collect Additional Data to Confirm Compliance

applying and responding to Monitoring Data 105 The ultimate purpose of a source investigation using root cause analyses or other investigative techniques is to identify the source and extent of the issue causing the water quality concern such that solutions to the issue can be developed and the airport can meet its compliance require- ments. A source investigation does not necessarily have to use root cause analysis techniques, but those techniques are recommended. A root cause analysis is a problem-solving technique used to identify core factor(s) triggering an issue. A factor can be considered a root cause if removal of the factor prevents the ultimate issue from recurring. If removal of the factor affects the ultimate issue but does not “solve” it, the factors can be considered a contributing factor but not a root cause. In some cases, multiple factors may interact to be a root cause. The term “removal of the factor” can be somewhat loosely applied. In some cases, it may mean true elimination (e.g., stopping use of a pesticide that is adding phospho- rus to the water or requiring aircraft not to park beyond designated areas when deicing). In other cases, removal could involve limiting the magnitude of the factor or adjusting the timing. Finding the root cause(s) is important. If only contributing causes are identified, but not the root of the issue, solutions to the issue could be treating symptoms rather than causes. For example, a common historical response to low dissolved oxygen concentrations associated with deicing has been to aerate the water near the stormwater discharge point. The low dissolved oxygen is a symptom of the issue, caused by too much deicer biodegrading. Adding oxygen does not address the excess deicer (typically the amount of oxygen demand from the deicer is many times greater than the oxygen that can be supplied by aeration, which is why aeration alone does not work). Ultimately the issue requires reduction in the quantity of deicer getting into the stormwater upstream of the monitoring point. The following Topical Tips box presents the core principles for conducting a root cause analysis. Topical Tips Core Principles for Conducting a Root Cause Analysis • Identify root cause analysis objectives, including the following: – Identify the factors that resulted in environmental consequence, including the magnitude, location, and timing of the issue – Determine what activities, actions, or conditions have to change to prevent recurrence – Identify lessons learned and apply them to future activities • Perform the root cause analysis systematically. • Write a clear problem statement and objectives for the analysis. • Seek the input of those with potential knowledge of the system for brainstorming. • Understand that there might be resistance to a root cause analysis and its findings because it may point out system or personnel shortcomings, may result in the need to challenge the status quo, and may result in the need to make compromises in other areas to solve the problem. • Draft a root cause analysis plan, using graphics such as a flow chart if possible. • Document the root cause analysis well. • Consider the cost–risk–benefit relationships for conducting the root cause analysis. Costs will be incurred both in the execution of the analysis and potentially to address the root cause. The risk analysis should con- sider both the risks of executing and not executing the root cause analysis. In some situations, an adaptive management approach that involves executing the analysis in phases may help manage cost and complexity. • If possible, identified root causes should be field tested to verify findings. In some cases, modeling of root cause effects may be possible.

106 Interpreting the results of airport Water Monitoring Several root cause analysis techniques can be applied to water quality or quantity issues, including the following: 1. Time Sequencing a. Graphically establish a sequence of events or timeline that graphically represents poten- tially causal factors. 2. Hierarchical Tracking a. Identify the potential factors contributing to the outcome. b. Review the parameters defining the factors and assess if the factors were operating within normal parameters at the time of the event. c. Determine the relationships among the factors and consider potentially interactive effects. Sometimes, if all factors are operating within normal parameter settings, an unusual com- bination of factor conditions may create an issue (i.e., the perfect storm). d. Use a graphical technique such as a fishbone (cause and effect) diagram to illustrate factors and relationships. Other potential graphical techniques include a Pareto chart (bar chart quan- titatively showing which factors are more significant) and a scatter plot (plotting impacts of two variables against each other to help understand relationships). Figure 23 is an example of a fishbone diagram with categories of potential contributors and specific causes listed. e. Through process of elimination, deduce the likely causes. f. If no known factors appear to be the root cause, begin the search for unexpected factors. Figure 23. Example of a fishbone (cause and effect) chart.

applying and responding to Monitoring Data 107 3. Upstream Tracing a. For stormwater systems, the source of a pollutant issue can sometimes be pinpointed by track- ing flow rates and/or pollutants starting at the most downstream point and systematically working upstream in the storm sewer network. Be aware that a successful root cause analysis depends upon the ability to obtain accurate data and the ability to sufficiently understand the factors and their relationships. When dealing with stormwater issues, it is virtually impossible to completely understand all processes. For example, stormwater infiltration into the soils can be highly variable, depending upon existing ground- water levels, soil conditions, drainage infrastructure condition, land use, and storm intensity. Conducting an upstream tracing study under dry conditions in summer with a vegetative surface versus the same study in winter conditions may yield different stormwater drainage patterns, resulting in significantly different pollutant concentrations. These differences could affect con- clusions. While not all factors can be completely understood, being aware of the complexities can inform the root cause analysis and the contingencies needed in the conclusions. 3.3.5 Collect Additional Data to Confirm Compliance At any point in the process of responding to a regulatory compli- ance issue, collection of additional monitoring data may be needed to provide information on unknowns or to help conduct a root cause analysis. In many cases, a final monitoring data collection effort may be needed to confirm the compliance status for the stormwater discharges. If the source of the compliance issue is known and the airport has taken actions to remedy the situation, this data may be used for the following: • To confirm the issue was an isolated incident • To confirm the average stormwater discharge for the month or reporting period is within the limits • To verify that a spill has been adequately cleaned up, or to confirm the performance of a new or improved control measure • To support a root cause analysis to determine the source of the issue • To understand the impact of the non-compliant stormwater discharges on receiving water quality Once additional data has been collected, it should be provided to the regulator for review and, if appropriate, confirmation that the compliance issue is closed. Key Takeaways Responding to Regulatory Compliance Issues • Identify if the compliance issue is strictly historical or ongoing—this will help determine the urgency of the response and the schedule for activities. • When a known or potential compliance issue arises, document what is known about the issue, its effects, and its causes. • Be clear on the regulatory reporting requirements and the compliance impacts. • Investigate and document supporting data regarding ambient conditions, reported incidents, operational changes, and maintenance issues. Define the Issue Review Related Existing Data Coordinate with the Regulator Conduct Source and Root Cause Investigations Collect Additional Data to Confirm Compliance

108 Interpreting the results of airport Water Monitoring 3.4 Application 2: Using Data in Establishing Permit Conditions Monitoring data collected by airports can also be used to support future regulatory activities. These can include permit re-applications or establishing new or modified permit conditions. Conducting monitoring in support of a new or modified permit characterizes the quality and quantity of stormwater discharges to enable regulators to assess the risk of future stormwater discharges exceeding water quality standards. For individual permit holders, the regulator uses monitoring data to determine what permit conditions are needed to demonstrate protection of the water quality in the receiving stream, including visual inspections, monitoring of specific parameters, effluent limits, and benchmarks. For standard 5-year NPDES permit renewal applications, airports must submit data on known pollutants. Most NPDES permit renewals are routine and no new monitoring data col- lection may be needed. In some cases, significant changes to airport operations (e.g., new main- tenance shop in previously undeveloped drainage area) or a change in applicable regulatory standards (e.g., water quality standards, TMDLs) may require collection of new stormwater monitoring data. This could potentially involve new parameters or existing parameters in new drainage areas. As described in Chapter 1, discharge permit modifications represent a special case of the permitting process. Permit modifications can be driven by a variety of circumstances that significantly change stormwater pollutant composition and the likelihood of pollutants being present in stormwater at a specific outfall in the middle of the permit cycle. Depending on the changes in pollutant loads, changes to permit conditions could include revisions to numeric criteria, monitoring frequency, monitoring parameters or analytical methods, or monitoring locations. 3.4.1 Developing Permit Conditions The process for initially setting or modifying numeric permit limits and monitoring require- ments often involves a “reasonable potential analysis.” A reasonable potential analysis is used to “determine whether a discharge, alone or in combination with other sources of pollutants to a waterbody and under a set of conditions arrived at by making a series of reasonable assump- tions, could lead to an excursion above an applicable water quality standard” (U.S. EPA, 2010). For more information about determining drivers for conducting monitoring to propose or establish permit conditions, see: 1.3.2 Monitoring Not Directly Prescribed in Discharge Permits 3.4 Application 2: Using Data in Establishing Permit Conditions • Use a formalized evaluation method, such as a root cause analysis, to assess the source and cause of the issues. • If possible, test the identified root cause by its removal or adjustment. • Be diligent in vetting whether a cause is a “contributing” cause or an actual root cause. • Many compliance issues are compounded by a shortage of data to characterize the extent and timing of the issue, implement corrective measures, and deter- mine if it has been resolved. • Weigh costs versus benefits and risks of collecting additional data. • Clarify reporting requirements for additional data collected. • If assumptions are made instead of collecting data, test the sensitivity of the result or corrective action to the assumptions.

applying and responding to Monitoring Data 109 It is a process regulators use to determine whether a water quality-based effluent limit and/or routine monitoring is required in an NPDES permit. The regulator often uses data collected by the airport to conduct the reasonable potential analysis. The airport may also choose to collect monitoring data and even prepare calculations to support the analysis. As a result, having an understanding of the role of monitoring in the overall reasonable potential process, as described in the following subsection, is beneficial. Reasonable Potential Analysis A reasonable potential analysis assesses the likelihood that potentially discharged pollutants will be present at quantities that exceed potential effluent limitations and result in an exceedance of numeric water quality criteria in the receiving water body. The first step in the reasonable potential analysis process is identifying potential pollutants of concern. Potential pollutants of concern can be identified from sources such as the following: • Effluent limit in a previous permit • Technology-based effluent limits • Waste load allocation from a TMDL • CWA Section 303(d) lists for the receiving waters • Past monitoring data • Pollutants projected to be present in the stormwater discharge based upon the industrial activities at the airport The reasonable potential analysis is conducted on the pollutants suspected to be present. The monitoring data characterizing the pollutant concentrations can be derived from past data or data collected as part of the reasonable potential analysis. Numeric criteria for the protection of a water body’s designated uses can be used as the base- line for establishing effluent limitations at the airport outfall discharge. The use designation for the receiving stream may have criteria for uses such as aquatic life, human health, drinking water, recreational waters, commercial use, and agricultural use. The use designations for each water body can be typically found on regulator’s websites. The aquatic life use designation typi- cally drives the applicable water quality standards at most airports. In other words, the typical monitored and limited parameters for many airport’s outfalls such as BOD, COD, dissolved oxygen, TSS, pH, and ammonia are derived from aquatic life water quality standards. In some cases, human health criteria, recreational use criteria, drinking water criteria, or agricultural use criteria may add parameters or provide more restrictive limits for airport NPDES permits, but this is relatively rare. For example, an airport whose surface water discharges are upstream of a raw water intake for a drinking water reservoir or treatment facility may have restrictions for TOC applied to its discharges. Numeric criteria can also be derived from other sources including the following: • Pollutant load allocations derived from receiving water body TMDL • Requirements to avoid impacts to threatened or endangered species. While threatened or endangered species-driven criteria are not especially common, when applicable, they can be problematic because of their potential to regulate difficult to control parameters (e.g., metals) at very low concentrations. If no mixing zone is allowed in the stream, the most restrictive numeric criteria for a given parameter becomes the effluent limit for the airport stormwater discharge. If a mixing zone is allowed, a waste load allocation calculation is performed to determine the maximum pollutant concentration that can be discharged from an outfall that allows in-stream water quality criteria to be met at the edge of the mixing zone. Figure 24 illustrates the waste load allocation mass balance.

110 Interpreting the results of airport Water Monitoring Mass Flow Pollutant Concentration Cr Qs Cs Qd Cd / Qr   ( ) = = + Where: Qs = Receiving water flow upstream of the stormwater discharge Cs = Background pollutant concentration in the receiving water Qd = Stormwater discharge flow Cd = Pollutant concentration in the stormwater discharge Qr = Resultant flow downstream of the stormwater discharge Cr = Resultant pollutant concentration in the receiving water The waste load allocation calculation is a mass balance calculation that takes into account flows and pollutant concentrations upstream of the potential discharge. Flow rates from poten- tial discharge are also part of the calculation, which requires determination of flow rates from the airport outfall. Because flow rates in the stormwater discharge and receiving water play a key role in the reasonable potential calculations, collection of additional flow data may be beneficial to the airport. Flow rate data for the stream is also necessary for the calculation. Without sufficient pollutant and flow monitoring data to support a reasonable potential analysis, the regulator may need to make conservative assumptions that can result in lower effluent limits than are really needed to protect the stream. As a result, it is recommended that airports invest in the data collection efforts associated with developing effluent limitations and monitoring requirements. Use Attainability Analysis In rare cases, a use attainability analysis can be performed in an attempt to reclassify a receiving stream’s use designation, which may affect the applicable water quality criteria. Executing a use attainability analysis typically requires collection of in-stream monitoring data to support the case. Should an airport have reason to believe that its receiving waters are not appropriately catego- rized, a use attainability analysis could be discussed with the regulator. The airport or regulator would need to provide data proving that the receiving waters are not used and do not have the For more information about monitoring for flow, see: 2.3.6 Applicability Ranges and Errors in Flow Monitoring Discharge (Qd, Cd)Upstream (Qs, Cs) Downstream (Qr, Cr) Figure 24. Waste load allocation mass balance equation.

applying and responding to Monitoring Data 111 potential to be used for the purposes described in the use designation or that the use designation cannot be met because of factors outside the control of the discharger, such as the following: • Naturally occurring pollutant concentrations • Flow conditions • Human-caused conditions or sources of pollution that cannot be remedied or would cause more environmental damage to correct than to leave in place • Hydrologic modifications that preclude the attainment of the use • Physical conditions related to the natural features of the water body • Controls would result in substantial and widespread economic and social impact [Water Quality Standards, 40 CFR §131.10 (1983, Revised 2015)] It is difficult to change a designated use, but, in some cases, it may be a viable option. Significant monitoring data may be required to make a case for a change. 3.4.2 Discussing Monitoring Frequency with Regulators Monitoring data can be used to support an increase or decrease in monitoring frequency. Airports have discretion to add more monitoring data and report it as required. This may be appropriate in situations such as collecting more data to achieve a more representative quanti- fication of the monthly average concentration of a pollutant. Airports can work with regulators to request reductions in monitoring frequency for parameters that are rarely, or have never been, detected at a location in concentrations close to the water quality limit. A reduction in monitoring frequency may be warranted if collected data illustrates that pollut- ant concentrations are lower or less varied than the concentration profile that was used during devel- opment of the existing permit conditions. Often, frequent monitoring is prescribed for parameters used to measure pollutants that, based on airport activities, may be present in stormwater discharges, but for which there was little or no existing monitoring data available to characterize the risk of exceeding the water quality limit. After the end of a permit cycle, monitoring data may be used to characterize that risk, and less frequent monitoring during the next permit cycle may be appropriate. 3.4.3 Proposing Alternative Monitoring Parameters and Methods An airport may propose use of an alternate monitoring method for a parameter, or monitor- ing of an alternate parameter to characterize a pollutant, when the existing monitoring method or parameter is problematic. Reasons for proposing alternate monitoring methods or param- eters are described in the following Topical Tips box. For more information about proposing reductions to monitoring frequency, see: U.S. EPA Interim Guidance for Performance-Based Reduction of NPDES Permit Monitoring Frequencies Topical Tips Reasons for Proposing Alternate Monitoring Methods or Parameters • Prescribed method quantification limit is greater than water quality limit. • Time required to conduct prescribed method does not allow for timely decision making in response to data. • Other constituents in stormwater are interfering with accuracy of measurements. • Given the location of the laboratory, the airport has difficulty meeting the required hold time for the method. • Airport cannot find a laboratory qualified to conduct the required analysis. • There is not a U.S. EPA-approved method for the required parameter. • Prescribed method is expensive, and a less expensive method will provide equivalent or better quality data.

112 Interpreting the results of airport Water Monitoring Alternate Monitoring Methods When proposing an alternate monitoring method, the onus is on the airport to prove that the alternate monitoring method can adequately characterize the presence and concentration of the potential target pollutant in the stormwater discharge. The alternate method should be able to quantify the concentration with the desired level of accuracy at the water quality limit. The airport should review the required hold time and confirm (1) that a laboratory is available that is qualified to conduct the analysis and can meet the required hold time and (2) that the analysis time and hold time for the proposed method are short enough to allow the airport to make timely decisions based on monitoring data results. Potential interferences with other constituents in airport stormwater should be investigated to determine if there are potential concerns with data accuracy associated with interferences using the alternate method. Use of Surrogate Testing Parameters In some instances, a monitoring method that meets the cost, timing, or accuracy needs of the airport and regulator is not available for a parameter. In these cases, a surrogate monitor- ing parameter may be acceptable. A surrogate parameter is used to represent the parameter of interest. To be used, a mathematical relationship must be able to be established between the parameter of interest and the surrogate parameter. Because stormwater at any given site is a mix of unique constituents, the correlation between a parameter and its surrogate often has to be established using monitoring data collected at that site. Even then, care must be taken to ensure that the mathematical relationship is valid across the range of conditions experienced. Table 10 identifies some parameters typically used as surrogates and the parameters that the surrogates are used to represent. 3.4.4 Proposing Alternate Monitoring Locations Monitoring data may also be used to support proposal of an alternate monitoring location or removal of a monitoring location. Section 1.5 provides guidance on choosing the ideal monitoring location. Proposing an alternate monitoring location may be advisable if hazards are present at the prescribed monitoring location that prevent safe conduct of monitoring activities, or other characteristics at the prescribed monitoring location prohibit collection of field conditions data, or collection of data that is representative of the airport stormwater discharges. Representative Outfalls Commonly, monitoring data is used to propose elimination of monitoring at outfalls that would otherwise require monitoring in permits. In those situations, a single monitor- ing location could potentially be deemed as “representative” of outfalls where monitoring is eliminated. Regulatory agencies may have specific protocols for demonstrating representative outfalls. Those demonstrations may require collection of monitoring data at the locations being considered. For more information about interferences from other stormwater constituents, see: Customizable Parameter Fact Sheet Tool For more information about choosing the ideal monitor- ing location, see: 1.5 Identifying Monitoring Locations For more information about evaluating representative outfalls, see: 1.5.2 Selection of a Repre- sentative Location Surrogate Parameter Parameter TOC BOD, COD, propylene glycol, ethylene glycol COD BOD, propylene glycol, ethylene glycol Oil and Grease BTEX, ORO TPH DRO, GRO, ORO, BTEX Table 10. Typical surrogate parameters.

applying and responding to Monitoring Data 113 3.5 Application 3: Applying Monitoring Data to Support Operations and Improve Airport Stormwater Quality Airports often have need for monitoring of water streams to support a variety of activities not directly associated with permit compliance or development of new or modified permits. For many of these activities, the primary purpose of collecting water monitoring data is to support ongoing planning, design, operations, and maintenance activities. Airports may also choose to execute water monitoring to support their broader environmental and sustain- ability goals. Several categories of these water monitoring activities are discussed in the following sections. 3.5.1 Planning and Design Stormwater management infrastructure can be a significant investment for airports, run- ning from thousands to millions of dollars. Selection, sizing, and design of the infrastructure frequently rely on accurate water monitoring data. The following stormwater infrastructure typically requires use of pollutant monitoring and flow data: • Deicer management infrastructure – Stormwater monitoring devices – Stormwater conveyance lines – Storage structures – Treatment facilities Key Takeaways Applying Monitoring Data to Establish Permit Conditions • Collecting monitoring data to support NPDES permit applications may reduce the need for permit-required monitoring in the next 5-year permit cycle. • Changes in operations or development may change the mix and quantities of pollutants at outfalls. When permit renewal applications are being developed, characterize airport changes since the last permit and conduct water monitoring to verify changes, or lack thereof, in pollutants at the outfalls. • Monitoring data can be used to reduce the number of outfalls where monitor- ing is required. • Airports can often benefit from being proactive in collecting monitoring data when new permit monitoring requirements or limits are being established as part of a reasonable potential analysis process. Regulators will take a more conservative approach if data is lacking. • Track monitoring data results by parameter and consider making a case with regulators for parameters to be dropped or monitoring frequency reduced in the next permit cycle if pollutant concentrations are consistently low. • Consider proposing use of surrogate parameters to replace permit-required parameters if there are cost or timing benefits. Use site-specific correlations to make the case.

114 Interpreting the results of airport Water Monitoring • Stormwater BMP controls – Low impact development infiltration–based controls b Swales b Filter strips b Bioretention basins b Permeable pavement – Cartridge filter systems – Detention and settling basins – Constructed wetlands – Oil–water separators • Remediation systems The types of pollutants and the extent of the monitoring data needed to support the selec- tion, sizing, and design of stormwater infrastructure vary. The extent that field monitoring data is needed also depends upon the extent to which model estimates are used. Model esti- mates may be less accurate than field-measured data because models rely on use of equations to represent complex processes. However, models have the advantage of simulating a much wider range of conditions, with the result that a more representative range of field condi- tions can be represented with models than with field data collection. Field monitoring data is also often needed to provide calibration and validation of stormwater quality and quantity models. In cases where monitoring data is needed to support selection, sizing, and design of storm- water infrastructure, decisions on the use of field-measured data versus model estimates must be made on a case-by-case basis. The factors in the Topical Tips box should be considered when making the model estimates versus field data decision. Topical Tips Factors to Consider When Deciding Between Modeled Data and Field Monitoring Data • Cost of field data collection versus cost of model development • Likely range of field conditions that can be captured – Field-collected data is more limiting than models • Length of time to collect field data under broad range of conditions versus time to develop, calibrate, and use a model – Both methods can be time-intensive, but field data collection relies on rep- resentative conditions being present. If they are not, the time required to collect appropriate field data often exceeds the time required for model development. • Potential future uses of models to simulate other conditions that require exploration – Future use of models provides clear advantage. • Accessibility to field sampling points • Assumptions that need to be made to develop model and potential sensitivity of the results to those assumptions – If too many assumptions have to be made or the model results are sensitive to the assumptions, field data collection may be preferable.

applying and responding to Monitoring Data 115 3.5.2 Management of Ongoing Operations and Maintenance Activities Most airports have some type of stormwater control infrastructure to manage water quantity and quality. Typical functions for the stormwater infrastructure include the following: • Monitoring systems for flow and pollutant concentrations • Mechanisms such as valves, gates, weirs, and pump stations for segregating flows of different pollutant concentration • Storage of stormwater of varying pollutant types and concentrations • Oil–water separator units • Stormwater BMP controls intended to remove solids and attached pollutants (e.g., metals, PAH, pathogens) • Biological treatment systems to reduce BOD, COD, and nutrient concentrations These systems require varying degrees of operational control and maintenance. Water moni- toring data often plays a significant role in effective operations and maintenance. Common uses for water monitoring data in operation of stormwater infrastructure include the following: • Determining pollutant concentrations to facilitate segregation of stormwater into fractions of varying concentrations (e.g., splitting flows into “concentrated” and “dilute” streams). The primary objectives of such segregation are to: – Meet permit limits for one or more of the segregated streams – Minimize the volume of water to be pumped, stored, or treated – Align concentrations of streams with treatment facility’s capabilities • Measuring treatment effluent pollutant concentrations to meet permit limits • Measuring treatment effluent pollutant concentrations to meet general permit requirements for monitoring (often the case if technology-based standards are applied) • Measuring treatment efficiency (e.g., measuring concentrations of a pollutant before and after the treatment unit) • Measuring various parameters internal to a treatment operation for the purposes of process control (e.g., dissolved oxygen, nutrient concentrations) – Grab samples and analysis for periodic checks – Online monitoring of various parameters (e.g., temperature, pH, dissolved oxygen) for the purposes of automated control system adjustments • Measuring flow rates and treatment concentrations for the purposes of calculating fees for discharges to a sanitary sewer Common uses for water monitoring data associated with maintenance of these systems include the following: • Measuring overflow or “breakthrough” of pollutants when a treatment unit’s capacity to remove pollutants has been maximized and actions are needed to maintain the unit – Oil–water separators reaching maximum fuel-holding capacity – Cartridge filter systems reaching maximum solids-holding capacity – Settling basins accumulating too many solids, resulting in washout of solids or reductions in detention time that do not allow sufficient settling time • Tracking of spikes in monitored readings that could be indicative of a maintenance issue, for example: – Flow monitoring probe breaking loose or being covered with sediment will produce unusual readings – Step-change in dissolved oxygen readings as a result of probe fouling • Tracking long-term changes in performance as system components age, such as pH monitor drift due to biological fouling of the probe • Evaluating issues that have arisen as a result of maintenance problems

116 Interpreting the results of airport Water Monitoring The monitoring associated with operations and maintenance typically falls into two types: • Periodic or as-needed monitoring via grab samples/laboratory analysis or handheld instruments • Real-time monitoring – Monitored data made available to operators on computer screens to see trends and outliers – Data linked to control system for computer-control automatic process adjustments such as opening valves, chemical dosing, and collecting samples The type of monitoring needed to support stormwater infrastructure operations and mainte- nance is situation specific. Considerations in selecting the monitoring parameters, types, methods, extent, and frequency include the following: • How quickly is the data needed? – Processes that require fast adjustments to control parameters likely require online monitor- ing tied into a SCADA system. – Processes that do not experience significant short-term fluctuations or that are less sensi- tive to system upsets can more likely be serviced with handheld-device monitoring or grab samples with laboratory analysis. – Processes that require monitoring data in less than a day’s time require online monitoring, use of handheld instruments, or grab samples that are analyzed by the airport with on-site instruments. • How sensitive is the operation to the accuracy of the data? – All monitoring instruments have ranges of applicability and limitations on sensitivity. – Instruments applied in field conditions may be less accurate than indicated in specifications provided by manufacturers due to variability in field conditions based on factors such as: b Biofilm growth on probe heads can affect readings. b Parameters like pH, temperature, TDS, and alkalinity may be in ranges that affect readings. b Individual constituents in the stormwater being monitored may interfere with the instru- ment measuring processes. b Fouling of the sample collection and conveyance system for the instrument can cause inaccurate readings. • What quantity of data is needed? – If large amounts of data are needed, it could be cost and time prohibitive to collect grab samples, perform the analyses, and manage the data. – Online monitoring requires more capital investment but can reduce operator time require- ments significantly and provide data during off-hours. • What monitoring parameters are needed? – Online monitoring instruments are available for a select number of parameters. – Online instruments typically are not available or do not provide sufficient accuracy for specific organic constituents. The recommendations in the Topical Tips box are for use of water monitoring in operations and maintenance of stormwater management systems. Topical Tips Recommendations for Use of Water Monitoring Data in Operation and Maintenance of Stormwater Management Systems and Control Measures 1. Identify the parameters that need to be monitored for both operations and maintenance.

applying and responding to Monitoring Data 117 3.5.3 Tracking and Improving Environmental Performance Discharge permit limits and benchmarks often “set the floor” regarding water quality and environmental performance. Airports may have policies and goals in place to further improve water quality or manage environmental performance to reduce the likelihood that water quality issues arise. Mechanisms for reaching those can be implemented in a variety of ways, including the following: • Sustainability policies • Sustainability management and tracking programs like Envision™ • Environmental management systems • Source reduction programs • Collaborative agreements with local stakeholders • Master plans to better position the airport for future development • Requirements for long-term progress in reducing pollutant loads in MS4 permits These mechanisms may involve the collection of water monitoring data for the purposes of tracking progress over time or evaluating the effects of specific water quality improvement initia- tives. The guidance for data acquisition and interpretation provided in Chapters 1 and 2 applies to data collected to support water quality improvements beyond minimum permit-required levels. It is recommended that airports take the steps regarding water monitoring found in the Topical Tips box when implementing these initiatives. 2. Evaluate if surrogate parameters can be used for needed parameters. Surro- gate measurements can be used if they are easier/less expensive to obtain and can be correlated to the desired parameter. 3. When selecting field monitoring instruments, be as specific as possible with the manufacturer regarding the conditions under which the instrument will operate and seek information on the effects of those conditions on accuracy. 4. Follow all instrument calibration recommendations. 5. Check field instrument and handheld instrument output against laboratory values to establish correlations using split samples. If necessary apply correla- tion factors to field-collected data. 6. Seek information from engineers, vendors, and other users of field instruments to understand time and resource commitments for maintenance. 7. Evaluate if monitoring data collected for the purposes of system operations and maintenance can also be used for permit compliance. If necessary, seek specific approval from regulators for use of non-standard field instrument data to meet permit reporting obligations. 8. In management of operations and maintenance data, align information on process conditions (set points, alarms, observations, performance data) with the monitoring data to facilitate appropriate interpretation of the monitoring data. 9. Understand which data collected for the purposes of system operations and maintenance monitoring needs to be reported to regulators.

118 Interpreting the results of airport Water Monitoring 3.6 Application 4: Stakeholder Communication and Public Outreach While not technically part of a monitoring program, effective public outreach can allow an airport to tout successes measured by the monitoring program and to manage public percep- tion of issues. Keys to effective public outreach include proactively disseminating information, particularly when related to an issue; providing appropriate background information to facili- tate complete understanding of the monitoring data provided; and anticipating and proactively responding to public concerns. This final section of the guidebook describes some tips for public outreach related to the airport monitoring program. 3.6.1 Conducting Effective Outreach All data submitted on monthly discharge reports is public information in the United States. Often that information is provided out of context. Airport management may consider a pro- active approach to sharing monitoring information and its context with the public. Providing information voluntarily, when not encumbered by a compliance issue, is one way to demonstrate transparency and establish a level of trust with the public. Providing information about the moni- toring program also serves to educate the public about the purpose for the monitoring, which demonstrates the airport’s commitment to protecting the environment. A key to effective public outreach is to provide appropriate information. A monthly spread- sheet with monitored results, or a time series plot of concentration, may not be particularly use- ful on its own. Worse yet, information provided without proper background could be subject to misinterpretation. For example, peaks in a time series plot of dissolved oxygen concentrations could be misinterpreted as peaks in a pollutant concentration if appropriate background infor- mation about dissolved oxygen is not provided. When providing monitoring data to the public, make sure to provide appropriate background information about the parameter. When providing monitoring information consider the message that is being conveyed as well as the appropriate amount of information, level of detail, and format that best supports the purpose of the message. For example, if the airport has implemented a series of controls over the past 5 years that resulted in significant reduction of metals concentrations at the outfall, then time series plots of metals concentrations over the past 5 years may be the most effective way of conveying this information. Adding labels to the timeline describing when each control was implemented may further demonstrate the correlation between airport investment in the controls and improvements in water quality of stormwater discharges. Adding key statistics demonstrating improvements can also add impact to graphical displays, for example, 90 percent Topical Tips Recommendations for Use of Water Monitoring Data to Track Progress in Improving Water Quality 1. Clearly define the goals for the water quality improvements 2. Define the uses of the water monitoring data 3. In stormwater monitoring databases, flag the purpose for the monitoring includ- ing whether the data is required by permit or intended to support larger goals 4. Understand the responsibilities for reporting or not reporting collected data to the regulator

applying and responding to Monitoring Data 119 reduction in effluent limit exceedances, or 10 percent reduction in metals concentrations at the outfall. Be cautious of providing tables of data that may be difficult to digest, or using statistics that are not commonly understood. Confusing or overly detailed information may be misinterpreted as intentional overcomplication in an effort to mask an issue. Managing Public Perception Managing public perception of the airport’s efforts to protect receiving water quality may be tricky, particularly if there are ongoing compliance issues. The first step to managing public per- ception is to identify the target audience, which could include local neighborhood groups; local, regional, or national environmental advocacy groups; local fishing clubs; local tourism groups; recreational groups; or the city council. The next step is to identify key concerns for the target audience. Drivers for interest in airport stormwater discharges could include concerns about airport stormwater discharges affecting the capacity of the waterway to support recreational use, odor complaints, negative effects on tourism from pollution, adverse effects to a public drinking water source, adverse effects to aquatic life or fishing, or health effects from swimming or fishing in water affected by airport stormwater discharges. Focus messages on how the airport is address- ing those concerns. Acknowledging that the airport is aware of public concerns and is working to address those concerns demonstrates a commitment to the community and the environment. If quantitative monitoring data is available that demonstrates improvements, be sure to highlight that information with a graph or statistic. Leverage qualitative initiatives directly or indirectly related to the stormwater monitoring program, like installation of a control measure, wetland mitigation for a project, or examples of public engagement like airport staff participation in river Topical Tips Questions to Consider when Assessing Background Information to Include with Public Dissemination of Monitoring Data • What parameter is being measured? • What is the purpose of monitoring this parameter? For example, the airport monitors oil and grease to detect the presence of fuels or oils in stormwater discharges associated with spills and leaks during fueling or maintenance. • What is the normal, acceptable range of concentrations for this parameter? • What is the water quality limit associated with the parameter? • What is the purpose of the water quality limit? Is it designed to protect aquatic life, preserve recreational uses, protect public water supply? • Is the water quality limit protecting acute or chronic exposure? • Is the long-term average or short-term maximum or minimum more important to consider from a water quality perspective? Why? • How do concentrations measured in airport discharges relate to water quality in the receiving waters? It may be useful to distinguish if airport runoff is the sole contributor of runoff to a receiving stream, or a very small contributor to a large receiving water. • What do the acronyms mean? Do not assume the public will know the mean- ing of DO, TOC, U.S. EPA, or the airport call sign. Clearly define important terms not part of the typical vernacular, and use simple language where pos- sible so the information can be understood by anyone interested.

120 Interpreting the results of airport Water Monitoring cleanup. Focus on examples of the positive impact of the airport on the community. Colorful brochures with photographs illustrating improved water quality or wildlife near the airport help illustrate a positive connection between the airport and the environment. Handling Public Concerns About Increases in Water Quality Impacts from Airport Development A proactive approach to public outreach is especially important when planning for airport development projects. The public often expresses concern about what impacts airport improve- ment projects may have on the environment. Providing the public with information about the airport’s plan for implementing control measures during construction and operation of new development areas may help ease concerns. Describing the airport’s plan to monitor stormwater discharges from potentially affected outfalls during construction and operation of new develop- ment as well as its plan to provide the public with information from the water quality monitor- ing efforts during construction and operation demonstrates transparency and can build trust. 3.6.2 Handling Non-compliance Incidents Despite an airport’s proactive communication about efforts to protect water quality, non- compliance incidents do occur. Effective public outreach related to non-compliance incidents is critical to maintaining a good relationship with the public and public interest groups. Effective handling of non-compliance incidents acknowledges the issue. Focus communications on the airport’s timely response, any data that demonstrates that the non-compliance has been rem- edied, and discussion of measures implemented to prevent or reduce the risk of recurrence of the issue. If appropriate, discussion of the extenuating circumstances leading to the non-compliance, like a 100-year storm or blizzard, may help to assuage fears of recurring non-compliance. Ulti- mately, the key to managing public perception is to understand the public’s concerns and to provide proactive, informative, and transparent information about airport monitoring.

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TRB's Airport Cooperative Research Program (ACRP) Research Report 166: Interpreting the Results of Airport Water Monitoring provides comprehensive guidance and a set of tools that operators of airports of varying sizes can use to understand, diagnose, and interpret airport water quality. This guidebook addresses water leaving the airport that does not go to an off-site treatment facility. Accompanying the report are the following tools to assist practitioners in diagnosing root causes and possible sources of specific problems that may require attention or mitigation:

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