A Guidebook for Airport Winter Operations (2015)

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15 Regulation of Winter Operation Impacts on Stormwater Planning for winter operations requires identifying applicable laws and regulations, under­ standing their implications, and incorporating operational and infrastructure controls to achieve and maintain compliance. Typical winter operations planning activities are understandably focused on compliance with regulations and ACs intended to maintain safe and efficient airport and aircraft operations, as described in Chapter 3. However, familiarity with the laws and regula­ tions intended to control the impact that winter operations have on the environment, including on stormwater runoff quality, is also important and expected. Routine operations at an airport are subject to extensive environmental regulation. ACRP Report 43: Guidebook of Practices for Improving Environmental Performance at Small Airports presents a summary of applicable federal reg­ ulations. ACRP Report 43 also identifies com­ mon regulated operational activities, including activities associated with winter operations, and potential regulatory compliance attain­ ment strategies. Additionally, it addresses the regulation of unplanned events, such as fuel spills during equipment fueling. Guidebook users are encouraged to review ACRP Report 43 if in need of a comprehensive overview of the airport environmental regulatory environment. However, this chapter focuses on the regulation of winter operation impacts on stormwater runoff quality and methods to mitigate these impacts. 4.1 Airport Winter Operation Activities Affecting Clean Water Act (CWA) Regulation and Compliance The most significant environmental concern associated with airport winter operations is the potential impact on airport stormwater runoff quality. Activities potentially impacting storm­ water runoff quality are strictly regulated under the federal CWA. Winter operations by their nature interact with, occur in response to, and require the management of precipitation and resultant stormwater runoff. Stormwater runoff enters storm drains and is routed through stormwater infrastructure to surface water bodies nearby the airport (e.g., streams, rivers, lakes, oceans, etc.). In some situations, stormwater can also be directed to the sanitary sewer. The C H A P T E R 4

16 A Guidebook for Airport Winter Operations following winter operation activities can affect stormwater runoff quality, and their potential impact on compliance with the CWA is described further in this section: • Application of various chemical deicers to aircraft, paved surfaces, and ground equipment; • Application of sand to paved surfaces; and • Storage and mechanical melting of deicer­contaminated snow. 4.1.1 Application of Chemical Deicers Chemical deicers are used during the winter season at most northern­tier airports. The term “chemical deicer” encom­ passes chemicals that assist in melting and preventing refreez­ ing of snow and ice (i.e., deicers) and chemicals that are used to prevent the adhesion of frozen precipitation on clean surfaces (i.e., anti­icers). Chemical deicers may be applied to aircraft as a liquid mixed with water, and to paved surfaces as a liquid or solid. Airport operators are typically responsible for appli­ cation of pavement deicers. Airport operators may not have direct control over the application of aircraft chemical deicers. However, once the applied aircraft deicers fall onto paved sur­ faces of airports, airport operators are typically responsible for managing the deicer­impacted stormwater in a manner com­ pliant with applicable environmental regulations and environ­ mental permits. This is accomplished through the planning, construction, and operation of a deicer management system. A detailed discussion of deicer management systems and their components is provided in Section 4.4. Chemical deicers can be problematic environmentally primarily because they contain highly biodegradable organic constituents. When those constituents are discharged to the storm sewers and to receiving waters, they begin to degrade if exposed to microbial organisms, typically in the form of bacteria. The bacteria use the organic components of the chemical deicers as a food source and in the process use oxygen dissolved in the water. If the levels of dissolved oxygen in receiving surface waters get low enough, fish and other aquatic organisms may be harmed. As such, minimum levels of dissolved oxygen in water bodies are often established by regula­ tory agencies, which lead to limitations on the quantities of biodegradable pollutants that can be discharged to those water bodies. Those limitations on substances that “demand oxygen” when biodegrading are often expressed in permits in terms of laboratory analyses designed to measure how much oxygen is used up when the deicers are biologically or chemically oxidized. This includes biochemical oxygen demand (BOD) and chemical oxygen demand (COD). Total organic carbon (TOC) is another laboratory measurement that is used to quantify how much organic chemical is present in a sample. In deicer­impacted stormwater, TOC can often be cor­ related reasonably well to BOD and COD and is, therefore, sometimes included in the effluent limitations or monitoring requirements of permits. The principal constituents of chemical deicers that are susceptible to biodegradation are the freezing point depressants, which most often are propylene glycol (PG) and ethylene glycol (EG), glycerin, acetates, and formates. Most aircraft deicers are glycol­based with some use of glycerin. Pavement deicers can include any of these constituents. Relatively speaking, PG presents the most significant oxygen demand, followed by glycerin, and then EG. While the oxygen­depleting characteristics of chemical deicers typically drive environmen­ tal permit requirements and the need for deicer management at most airports, other potential Source: Wausau Equipment Company

Regulation of Winter Operation Impacts on Stormwater 17 environmental effects of chemical deicers may be significant drivers for permit compliance and deicer management at some airports, including: • Toxicity (potentially from the freezing point depressants and deicer additives); • Odors; • Foaming; • Total dissolved solids (TDS) concentrations from the inorganic salt portion of pavement deicers like sodium formate and potassium acetate; and • Contribution to biofilm growth of receiving waters (i.e., nuisance growth). These effects could restrict the amount of the pollutants associated with deicers that are allowed to be discharged to surface waters. The importance of these factors as drivers for envi­ ronmental permit compliance and deicer management is site specific. Often their importance is driven by characteristics of the receiving stream, applicable state regulations, local regulatory environment, public input, and past history of environmental impacts. It is advisable for per­ sonnel managing winter operations to be aware of the potential environmental impacts that underlay environmental permit conditions and compliance expectations. 4.1.2 Application of Sand Sand is sometimes used instead of, or in conjunction with, chemical deicers to increase friction on runways, taxiways, and ramp areas. The sand is chemically inert, but it can contribute to the solids discharged to water bodies that receive airport stormwater runoff. Often, stormwater dis­ charge permits have requirements that limit and/or require monitoring of solids which are often quantified through an analytical parameter called total suspended solids (TSS). Application and subsequent transport of applied sand can increase the concentration of TSS in stormwater run­ off, which increases the potential for a violation of stormwater discharge permit criteria or cre­ ation of a water quality issue in the streams. In addition to potentially obstructing in­pavement lighting, sand can also build up, interfere with, and potentially damage the catch basins, pumps, pipes, tanks, and treatment units associated with deicer management systems, as well as with mechanical snowmelters. 4.1.3 Deicer-Contaminated Snow Storage and Mechanical Snow Melting Snow falling on paved surfaces is often plowed, broomed, or blown to adjacent perimeter and infield areas, or hauled to designated snow dumps. Both aircraft and pavement chemi­ cal deicers can be mixed with the snow (sometimes referred to as “pink snow” due to the dyes in the aircraft deicers). Natural melting of piled or stored snow can often occur over long periods of time. From an environmental standpoint, this often means a prolonged discharge of chemical deicers mixed within the snow well after the time of application. There is some evidence that chemical deicers may migrate from snow piles at rates faster than the rate the snow melts (the “snow cone effect”), resulting in discharges of high concentrations of BOD and presenting a deicer management and permit compli­ ance challenge (6). Rain events and/or increases in tempera­ ture can also accelerate melting and chemical deicer discharge. For these reasons, collection and treatment of runoff may be required and provided through a deicer management system. Source: Gresham, Smith and Partners

18 A Guidebook for Airport Winter Operations It may be necessary, or simply advantageous, to mechanically melt snow. The procedure can take a variety of forms. Snowmelters may be permanently installed at a specified location or they may be mobile, meaning the melted snow discharges to different portions of the storm sewer system at different times. Mechanical snow melting can occur in close proximity to the source of the accumulated snowfall or in remote areas off the ramp where dedicated snow piles exist. Because of the variability in location and timing of mechanical snow melting operations, snow melting can have a significant effect on an airport operator’s ability to comply with its environ­ mental permits and the performance of its deicer management system. 4.2 National Pollutant Discharge Elimination System (NPDES) Stormwater Discharge Permitting Under the CWA Most winter operations occur in areas of airports that discharge stormwater runoff through a point source outfall to a receiving water body. The operations at airports are considered to be industrial activities and are, therefore, required to have one of two types of NPDES permits for industrial activities: a general NPDES permit that is applicable to a group of facilities, or an indi­ vidual NPDES permit issued specifically for a facility. A few airports are subject to both general and individual NPDES permits. The permitting agency will determine the required permit. To apply for a stormwater permit, an airport operator is typically required to submit a notice of intent. The assigned permit will then provide the criteria, conditions, and monitoring require­ ments that govern the allowable stormwater discharges. Familiarity with the NPDES permit is essential for appropriate winter operations planning and decision making. NPDES permits are issued with an effective duration of up to five years, and must be renewed, typically starting six months prior to expiration. It is not uncommon for permit limits and conditions to change when permits are renewed. Permit changes relevant to winter operations should be communicated during pre­season winter operations planning. 4.2.1 General NPDES Permits A general NPDES permit contains generic language that is applicable to the facilities covered under the permit. General NPDES permits may contain numeric effluent limitations or, more frequently, discharge benchmarks. Effluent limitations define the maximum or minimum extent of pollutants in a discharge. Often, those limits are in terms of concentrations (e.g., maximum BOD concentration) or mass loading (e.g., maximum kilo­ grams of TSS per day). Exceeding those limits can constitute a violation of the permit. If permit criteria are violated, the regulatory agency can require a series of compliance actions that can range from submitting a letter describing the reason for the exceedance to daily fines. Repeated permit violations or excessively high exceedances of criteria can result in the regula­ tory agency issuing orders or decrees for specific and poten­ tially costly actions to correct the issue. Individuals can also be held responsible for willful violation of permit conditions. Effluent benchmarks are less restrictive than effluent limits. If benchmarks are exceeded, the permittee does not incur a permit violation, although it may be required to implement additional practices to prevent further exceedances. If bench­ mark exceedances continue, more restrictive measures and Source: Gresham, Smith and Partners

Regulation of Winter Operation Impacts on Stormwater 19 fines can be required by the permitting authority. The authority could also potentially imple­ ment effluent limitations in place of benchmarks if it finds a reasonable potential for frequent exceedance of the benchmarks. General permits may contain requirements to perform monitoring of stormwater discharges, although the monitoring requirements are often less intensive than in individual NPDES permits. State agencies delegated authority to administer the NPDES program have issued general permits modeled after the U.S. Environmental Protection Agency (EPA) multi­sector general permit, which is only directly applicable to a small number of states that do not have their own NPDES permit­ ting authority. The multi­sector general permit includes requirements that apply specifically to air transportation facilities, including conditions associated with discharges from airfield and aircraft deicing activities. The multi­sector general permit includes effluent monitoring benchmark con­ centrations for COD (120 mg/L), five­day biochemical oxygen demand (BOD5) [30 milligrams per liter (mg/L)], ammonia­nitrogen (2.14 mg/L), and pH (6.0–9.0 standard units). In addition to monitoring stormwater discharges, a general NPDES permit typically includes requirements to: • Prepare an SWPPP for industrial activities (also refer to AC 150/5320­15A, Management of Airport Industrial Waste); • Conduct inspections; • Train employees; • Clean up spills; and • Implement BMPs. BMPs are processes, procedures, and structural controls to reduce the release of pollutants typically near the pollutant source. Some BMPs, such as those related to handling of deicer, would be implemented by winter operations staff. As a result, BMPs related to winter operations should be identified in winter operations plans and staff should be trained on the procedures. 4.2.2 Individual NPDES Permits Individual NPDES permits typically have specific numeric effluent limitations for one or more pollutants, and are usually required by the state agency or EPA in lieu of general permits based upon a higher concern for potential violations of water quality standards. Like general NPDES permits, individual NPDES permits include requirements for preparation of a SWPPP for implementation of BMPs. An individual NPDES permit will often include numeric effluent limits and, potentially, narrative criteria further limiting discharges. Often numeric limits are based on the values that will prevent water quality standards established for the receiving stream from being violated. Individual NPDES permits may also have numeric effluent limits derived from treatment­technology­based standards. 4.2.3 Effluent Limitations Guidelines (ELGs) and New Source Performance Standards (NSPSs) Airport NPDES permits may include technology­based ELGs to control airport deicing dis­ charges. According to the EPA Fact Sheet, “Effluent Guidelines for Airport Deicing Discharges,” the ELG requirements generally apply to chemical deicer­impacted stormwater (referred to as wastewater in the fact sheet) associated with the deicing of airfield pavement at primary airports. Specifically, the fact sheet identifies the following requirements: • “Existing and new primary airports with 1,000 or more annual jet departures (“non­propeller aircraft”) that generate wastewater [i.e., pavement deicer­impacted stormwater] associated

20 A Guidebook for Airport Winter Operations with airfield pavement deicing are to use non­urea­containing deicers, or alternatively, meet a numeric effluent limitation for ammonia [i.e., 14.7 mg/L, prior to dilution or mixing with non­deicer­impacted stormwater]” (7, p. 1). Additionally, certain NPDES permits may include NSPS applicable to the following subset of airports described in the fact sheet: • “New airports with 10,000 annual departures located in cold climate zones are required to collect 60 percent of aircraft deicing fluid after deicing. Airports that discharge the collected aircraft deicing fluid directly to waters of the U.S. must also meet numeric discharge require­ ments for COD [i.e., 271 mg/L daily maximum, 154 mg/L weekly average]. The rule does not establish uniform, national requirements for aircraft deicing discharges at existing airports. Such requirements will continue to be established in general permits, or for individual permits on a site­specific, best professional judgment basis” (7, pp. 1–2). The provision of the ELG associated with urea­based deicers is critical to understand for airport operators applying pavement deicers. While many airport operators have moved away from the formerly widespread use of urea to melt snow and ice on pavements, some airports still utilize urea or have provisions for use of urea on an emergency basis. The ELG rule does not outright ban use of urea; however, if an airport uses urea, even on an emergency basis, it must ensure that the concentration of ammonia­nitrogen in discharges to the surface waters does not exceed 14.7 mg/L. Since widespread use of urea can easily result in stormwater concentrations greater than 14.7 mg/L, airport operators who consider the continued use of urea may need to demonstrate a means for collecting and/or treating urea­impacted stormwater to reduce ammo­ nia concentrations to less than 14.7 mg/L. 4.2.4 Guidance for Interpreting Conditions in NPDES Permits The NPDES permits that govern the discharges of stormwater containing pollutants to sur­ face water bodies may have conditions that affect winter operations. Airfield maintenance and operations staff should consult the airport environmental staff or consultants involved in the permit development and regulatory agency coordination to help interpret the applicability of the permit conditions to winter operations. Knowledge of the permit structure and conditions can be useful in interpreting measures that need to be taken in response to the permit. The permits often have the following elements: • Listing of point source locations from which stormwater discharges are authorized, • Limitations on the quantity or concentration of various pollutants in the discharge, • Limitations on the volume or flow rate of stormwater that can be discharged, • Requirements for the monitoring of pollutant concentrations and flow rate/volume, Summary of ELG and NSPS Considerations for Airport Winter Operations • Use of urea as pavement deicer is banned unless ammonia concentrations at stormwater discharge points are less than 14.7 mg/L. • There are no national requirements for aircraft deicing discharges for existing U.S. airports. • COD effluent limits are applicable only to new airports with sufficient flight operations. • No specific type of deicer treatment technology is mandated. • ELG-driven conditions are incorporated into NPDES permits.

Regulation of Winter Operation Impacts on Stormwater 21 • Special conditions under which stormwater discharges are authorized or limited, and • Requirements for reporting monitoring data and observations. NPDES permits for industrial activities apply on a year-round basis, but may include criteria that vary by season. Seasonal criteria are typically listed in the section of NPDES permits where effluent limitations and monitoring require- ments are provided on an outfall-by-outfall basis. Criteria may be seasonal because receiving water bodies can assimilate pollutants to different extents in warmer and colder weather and because of the unique nature of winter operations at airports. Summer criteria can often be more stringent than win- ter criteria. At some airports, the management of snow piles or stored deicer- impacted stormwater can extend into the summer time frame in the NPDES permits. It is, therefore, important to be aware of winter versus summer differ- ences in permit conditions, including the dates at which the conditions change. For example, discharges from snow piles that may have met winter season per- mit limits might exceed summer season limits. It is important for airport operators to determine which permit limits repre- sent the most restrictive limits, or governing conditions, in the permit. For more guidance on determining governing conditions from permits and agreements, see ACRP Report 99: Guidance for Treatment of Airport Stormwater Containing Deicers. 4.3 Other Regulatory Programs Applicable to Airport Winter Operation Activities In addition to the NPDES permit program, airport winter operations may also be subject to additional regulation. Chemical deicer-impacted stormwater or applied deicer runoff may be regulated under a municipal separate storm sewer system (MS4) permit, if it is discharged into a stormwater conveyance system owned or operated by a public entity. Additionally, discharges into a sanitary sewer where the discharge is eventually treated at a publicly owned treatment works (POTW) may be regulated by the POTW under the national pretreatment program. For additional guidance on MS4 and pretreatment program requirements, see ACRP Report 99: Guidance for Treatment of Airport Stormwater Containing Deicers. 4.4 NPDES Compliance Through an Airport Deicer Management System If stormwater runoff from winter operations is likely to contain pollutants from deicer appli- cation at levels that have a reasonable potential to violate regulatory criteria and NPDES permit conditions, the stormwater must be managed to mitigate potential environmental impacts to Summary of NPDES Permitting Considerations for Airport Winter Operations • NPDES permits for industrial activities are the primary means for regulating discharge of deicer-impacted stormwater. • Effluent limits are based primarily on local water quality standards. • Different limits can apply in summer and winter. • Each drainage area and outfall can have different limits. • BMPs for managing stormwater may be required and are typically described in an SWPPP.

22 A Guidebook for Airport Winter Operations surface water and groundwater. The comprehensive, integrated system for managing deicer- impacted stormwater is called a deicer management system. 4.4.1 System Components Each airport’s deicer management system is different and may not include all of the compo- nents depicted in Figure 4-1. Most include some form of designated deicer application areas, stormwater monitoring, collection of impacted stormwater, and discharging stormwater in a way that meets permit conditions. Some airports required extensive systems for temporarily storing the stormwater, means for treating the stormwater onsite or offsite, and sophisticated processes for controlling the deicer management system as a whole. The components, capacities, coverage area, and complexity of an airport’s individual deicer management system are dependent upon local climate, aircraft operations, airport infrastructure, assimilative capacity of the local water bodies receiving the stormwater runoff, and regulatory requirements. 4.4.2 System Planning and Evaluation The planning and evaluation of deicer management system needs and the design of the systems can be a complex pro- cess that can take years. As a result, implementation of a deicer management system is often undertaken outside the strict confines of winter operations planning (see ACRP Report 14: Deicing Planning Guidelines and Practices for Stormwater Management Systems). However, coordination between those designing deicer management systems and those responsible for winter operations planning is essential. Critical areas that require coordination and common understanding include: • Deicer application locations, both for aircraft and pavement deicing; • Types and even specific brands of deicing chemicals; • Conditions under which deicer is applied; Figure 4-1. Schematic of potential deicer management system components (8, p. 2). Source: Gresham, Smith and Partners

Regulation of Winter Operation Impacts on Stormwater 23 • Method by which deicer is applied (e.g., use of hybrid forced air deicing units for aircraft deicing); • Tracking of deicer use; • Forecasting future deicer use; • Procedures for overnight parking and deicing aircraft; • Snow plowing and blowing practices; • Snow storage locations; • Snow melting procedures; and • Runway closure criteria and procedures. Winter operations staff should actively engage those charged with the design of a deicer management system to help ensure that designers have the best available information on these practices. This will maximize the likelihood that the implemented deicer management system is appropriately sized and capable of successfully operating under the variety of conditions that may be encountered. Designers of deicer management systems should seek to thor- oughly understand the winter operations practices and take steps to ensure that the overall winter operations practices are compatible with operational needs for deicer management systems. At some airports, winter operations staff has responsibilities for general winter operations and for deicer management system operation. Coordinating the timing and extent of operational needs for these two sets of responsibilities is essential. 4.4.3 Stormwater Runoff Monitoring (9) Monitoring of stormwater runoff is an integral element of regulatory compli- ance and a means for managing winter stormwater flows within a deicer man- agement system. This section presents a synopsis of ACRP Report 72: Guidebook for Selecting Methods to Monitor Airport and Aircraft Deicing Materials. Stormwater monitoring can allow the segregation of deicer-impacted stormwater into different fractions based on concentration. The objective is to collect and potentially treat only the stormwater that has pollutant concen- trations above permitted concentrations or loadings. Often in these types of systems, online monitors are used to get near-continuous measurements of flow rates and pollutant concentrations, with the results fed to a computer- based control system. If the measured values exceed predetermined set points, actions such as the opening or closing of a slide gate or the turning on or off of a pump are triggered, resulting in the routing of the stormwater to a particular location. Airports typically implement permit monitoring programs that involve sample collection and analysis for the monitoring parameter. Monitoring consists of two elements: collection of the sample and testing of the sample to quantify the param- eter in question. Sampling can be accomplished in a variety of ways, including: • Collection of individual samples by airport or hired staff. • Use of auto samplers that are programmed to collect samples at regular intervals or based on how much flow has passed. The auto samplers may be programmed to mix the individ- ual samples together (composite sample) or temporarily hold individual samples (discrete samples). • Use of specially designed sampling systems that may involve continuous or intermittent pumping of stormwater, typically to a continuous monitoring device.

24 A Guidebook for Airport Winter Operations The testing of the sample to quantify its characteristics typically occurs through analysis at an independent, certified analytical laboratory or analysis onsite at the airport using: • Analytical equipment permanently situated in the lab. • “Test kits,” which are smaller instruments that may provide results with a lesser degree of accuracy than laboratory equipment. This type of testing is used when the airport desires a faster turnaround time for the results. • Hand held instruments (e.g., a pH probe) that can be carried from point to point. • Test equipment permanently installed near the monitoring location. This method is used when a large quantity of data is required, but is limited to a relatively narrow band of parameters. Common analytical parameters for winter operations include: flow rate; flow volume in a day; BOD; COD; TSS; TDS; and levels of PG, EG, ammonia­nitrogen, phosphorus, pH, and tempera­ ture. It is recommended that airport personnel involved in winter operations understand the monitoring requirements, including: • Sample/monitor location; • Sample timing; • Conditions that trigger sampling/monitoring; and • Areas of the airport draining to each monitoring location. An understanding of this information and communication with airport personnel respon­ sible for sampling and permit compliance can result in more efficient monitoring with less risk of permit noncompliance. 4.4.4 Runoff Collection and Storage Deicer management systems have limitations in their ability to manage deicer­impacted stormwater. For most airports, the stormwater drainage areas are too vast for stormwater runoff from all areas to be collected with a deicer management sys­ tem. As a result, stormwater collection systems are limited to areas where collection is needed to meet regulatory criteria. In addition, at some airports, deicer application is limited to small areas, such as deicing pads, so that the volume of storm­ water impacted by deicers is minimized. Understanding the boundaries of the deicer application and stormwater collec­ tion is essential for winter operations staff. Deicing outside of these areas can directly lead to noncompliance with environ­ mental permits. If through operational needs or expansion it is not feasible to deice aircraft within areas served by the deicer management systems, other measures must be taken to achieve compliance. Instances where aircraft or pavement is deiced outside of the deicer management system collection areas should be noted and reported by winter operations staff. Many airports have storage vessels for temporarily containing deicer­impacted stormwater. The vessels may be underground tanks or pipes, lined or unlined lagoons, or aboveground stor­ age tanks. The storage vessels are typically sized to have enough storage for relatively extreme deicing seasons. However, they do not have unlimited capacity, and it is possible that condi­ tions may be encountered where storage capacity is temporarily unavailable. Sizing storage vol­ umes, along with other deicing management system components, should involve identifying an appropriate design storm event, as described in ACRP Report 81: Winter Design Storm Factor Source: Gresham, Smith and Partners

Regulation of Winter Operation Impacts on Stormwater 25 Determination for Airports. This process requires an understanding and analysis of airport-specific historical winter event data similar to the process described in Chapter 5 of this guidebook. Winter storm events that exceed the design storm conditions may result in the need to temporarily adjust operations, such as postponing mechanical snow melting until sufficient capacity is available. Communication between deicer management system staff and winter opera- tions staff in these circumstances is necessary. 4.4.5 Deicer-Impacted Stormwater Runoff Treatment (8) Some airports have, or are considering the addition of on-airport, deicer- impacted stormwater runoff treatment capabilities into their deicer manage- ment systems. This section presents a synopsis of the treatment discussion originally presented in ACRP Report 99: Guidance for Treatment of Airport Stormwater Containing Deicers. Deicer treatment is the component of a deicer management system that removes deicers from the deicer-stormwater runoff mixture. Deicer treatment can utilize physical or biological means to reduce the pollutant content of stormwater such that it can be discharged to the surface water body or sanitary sewer. Commonly used deicer treatment systems include membrane-based gly- col recycling systems, evaporation-based glycol recycling systems, and biological systems that use bacteria to degrade the deicer. Deicer treatment systems are usually designed specifically to remove or breakdown the chemical constituents in deicers and are not suitable to treat all pollut- ants. For example, biological treatment systems are not designed to treat the types of chemicals in jet fuel, especially at high concentrations. In fact a significant fuel spill could harm deicer treatment operations. As a result, it is important that deicer treatment systems not be used as a catch-all or dumping ground for water with pollutants other than deicers. Deicer treatment systems may also be designed to treat spe- cific types of deicer constituents. For example, many deicer recycling systems in the U.S. are intended to produce concen- trated PG. As designed, they are usually not set up to produce concentrated streams of EG or glycerin. Therefore, if changes to the type of deicer are considered, steps should be taken to ensure their compatibility with the deicer treatment operations. Finally, deicer treatment systems have defined maximum capacities. While many deicer management systems have means for “buffering” the treatment system through upstream storage or controlled discharge of pollutants into the treat- ment unit, some do not. Therefore, care must be taken with the release of spike loadings of deicer that discharge to the treatment system. This includes potential spike loadings from extended mechanical snow melting operations, dumping of deicer collected from glycol recovery vehicles into the collec- tion system, and spills of deicer. 4.4.6 Annual Operational Review Once deicer management systems have been implemented, there is often a learning curve associated with the operation, including the compatibility between the deicer management sys- tem operation and the remainder of winter operations. While the learning curve is often most Source: Gresham, Smith and Partners

26 A Guidebook for Airport Winter Operations steep in the first winter of operation of deicer management systems, each winter presents its own unique circumstances. As result, it is recommended that as each year’s winter operations planning is undertaken, a portion of the effort be devoted to discussing issues from the previous winter’s deicer management operations to determine if any changes to the winter operations plan or the deicer management operations should be undertaken for the next season. Aspects of the operations that should be routinely considered include: • NPDES permit violations that occurred in the previous winter and the causes, • Whether deicer application operations were able to be contained within areas served by the deicer management system, • Whether snow storage areas are appropriately sized to contain deicer­impacted snow, • Whether snow storage areas are located in areas that meet operational needs, • Whether deicer management operations affected the airport operator’s ability to perform winter operations as needed, • Anticipated changes in deicing chemicals, • Anticipated changes in deicing locations, and • Access and maintenance issues.