Impact of Airport Pavement Deicing Products on Aircraft and Airfield Infrastructure (2008)

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TABLE 2 TYPE OF PDP USED AT U.S. AIRPORTS DURING 2004/2005 WINTER SEASON Size Classification Chemical/Material Large Hub (17) Medium Hub (21) Small Hub (19) Non-Hub (44) Total Airside Urea 4 6 6 14 30 Sodium Form ate 1 6 3 3 13 Sodium Acetate 7 8 6 6 27 Potassium Acetate 14 18 16 20 68 Propylene Glycol-Based Fluids 3 0 2 4 9 Ethylene Glycol-Based Fluids 1 0 1 1 3 Sand 12 15 10 25 62 Notes: Data based on a subset of the data from the 2006 EPA questionnaire. Some airports used more than one PDP. 6 The EPA is in the process of developing effluent guide- lines for airport deicing. To this end, industry questionnaires were distributed and site visits and wastewater sampling were conducted. Based on responses to the in-depth questionnaire distributed in April 2006 to 152 airports, 130 of the 139 re- spondents conducted deicing activities (Strassler 2006). De- tailed responses concerning the type and amount of deicers applied at 102 airports were acquired by the ACRP synthesis team. As shown in Table 2, approximately 100 of the airports applied deicers during the 2004/2005 winter season. KAc and sand were used by a majority of airports, 68 and 62 re- sponses, respectively. Approximately 100 airports indicated the use of mechanical methods and 7 of these airports did not use any chemicals or sand. Thirty-nine airports re- ported using two different materials, 32 used three, and 18 used only one. Of the 18 airports that indicated using only one type of chemical, half used KAc, six applied sand, two applied airside urea, and only one used propylene glycol- based fluids. The type of PDP chemical or material used by airports based on their size classification: large-, medium-, small-, and non-hub, is presented in Table 2. Only the non-hub air- port size was associated with less than 50% usage of KAc. Of all the airside urea in use, most (74%) was applied at non- hub airports. Many of the respondents to the EPA questionnaire (49) also provided the amounts of chemicals applied during the 2002/2003, 2003/2004, and 2004/2005 winter seasons. These amounts are shown in Table 3 for the corresponding number of airports providing this information. The liquid chemicals were generally applied at 50% concentration; a few airports specified other concentrations. The selection of PDPs by airport staff can be based on many factors, including cost, effectiveness, environmental impact, risk of corrosion (to metals), and electrical conduc- tivity. Sixteen respondents to the ACRP survey chose to rate the importance of these five factors and any other criteria considered in the selection of PDPs at their representative airport. Numeric values were assigned to the level of impor- tance based on the range of response options: 1 = Unimportant, 2 = Not very important, 3 = Important 4 = Somewhat important, and 5 = Very important. Numerically, the average importance ranged from 3.5 to 4.9 across the criteria factors, with “effectiveness” ranked as the most important criterion and “electrical conductivity” as the least. The effectiveness criterion also exhibited the lowest standard deviation, with “corrosion risk” being the highest (Figure 2). Interestingly, no airport selected “unimportant” or “not very important” for any of the criteria options in the sur- vey, highlighting the challenges and dilemmas faced by the CHAPTER TWO USE OF AIRPORT PAVEMENT DEICING PRODUCTS AT AIRPORTS

7TABLE 3 AMOUNT OF DEICERS APPLIED AT THE REPORTING U.S. AIRPORTS DURING THREE WINTER SEASONS 2002/03 2003/04 2004/05 Chemical/Material No. Airports Amount No. Airports Amount No. Airports Amount Airside Urea (pounds) 14 2,056,988 16 4,330,356 17 2,451,914 Potassium Acetate (gallons) 35 4,146,441 36 4,598,292 36 2,792,393 Sodium Acetate (pounds) 13 5,068,222 12 5,764,147 16 4,365,449 Sand (pounds) 25 29,413,920 26 27,949,397 32 34,372,627 Sodium Formate (pounds) 5 248,283 6 486,813 7 365,073 Ethylene Glycol-Based Fluids (gallons) 1 373,185 1 151,118 1 261,887 Propylene Glycol-Based Fluids (gallons) 4 225,800 4 226,200 4 256,537 Note: Data based on a subset of the data from the 2006 EPA questionnaire. FIGURE 2 Importance of various criteria considered by airports for PDP selection; bars represent two standard deviations. 1 2 3 4 5 Effectiveness Environmental Impact Cost Corrosion Risk Electrical Conductivity Av er a ge Im po rta n ce airports pertinent to snow and ice control. A European airport filled in two “other” criteria: (1) impact on asphalt pavement and (2) impact on working environment, both considered “very important.” The high use of KAc at airports is consistent with both the general FAA preference to anti-icing practices and its more benign environmental impact compared with urea and gly- cols. The next chapter will discuss the impacts of PDPs on aircraft components. Although corrosion risk and electrical conductivity were judged least important compared with the other factors, the average response was still above “impor- tant.” However, their relative importance to airport staff implies that any new PDP formulations must not sacrifice effectiveness or environmental liability in looking for PDPs that may be more compatible with aircraft components.