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6 CHAPTER TWO USE OF AIRPORT PAVEMENT DEICING PRODUCTS AT AIRPORTS The EPA is in the process of developing effluent guide- 2002/2003, 2003/2004, and 2004/2005 winter seasons. These lines for airport deicing. To this end, industry questionnaires amounts are shown in Table 3 for the corresponding number were distributed and site visits and wastewater sampling were of airports providing this information. The liquid chemicals conducted. Based on responses to the in-depth questionnaire were generally applied at 50% concentration; a few airports distributed in April 2006 to 152 airports, 130 of the 139 re- specified other concentrations. spondents conducted deicing activities (Strassler 2006). De- tailed responses concerning the type and amount of deicers The selection of PDPs by airport staff can be based on applied at 102 airports were acquired by the ACRP synthesis many factors, including cost, effectiveness, environmental team. As shown in Table 2, approximately 100 of the airports impact, risk of corrosion (to metals), and electrical conduc- applied deicers during the 2004/2005 winter season. KAc tivity. Sixteen respondents to the ACRP survey chose to rate and sand were used by a majority of airports, 68 and 62 re- the importance of these five factors and any other criteria sponses, respectively. Approximately 100 airports indicated considered in the selection of PDPs at their representative the use of mechanical methods and 7 of these airports did airport. Numeric values were assigned to the level of impor- not use any chemicals or sand. Thirty-nine airports re- tance based on the range of response options: ported using two different materials, 32 used three, and 18 used only one. Of the 18 airports that indicated using only 1 = Unimportant, one type of chemical, half used KAc, six applied sand, two 2 = Not very important, applied airside urea, and only one used propylene glycol- 3 = Important based fluids. 4 = Somewhat important, and 5 = Very important. The type of PDP chemical or material used by airports based on their size classification: large-, medium-, small-, Numerically, the average importance ranged from 3.5 to and non-hub, is presented in Table 2. Only the non-hub air- 4.9 across the criteria factors, with "effectiveness" ranked as port size was associated with less than 50% usage of KAc. the most important criterion and "electrical conductivity" as Of all the airside urea in use, most (74%) was applied at non- the least. The effectiveness criterion also exhibited the lowest hub airports. standard deviation, with "corrosion risk" being the highest (Figure 2). Interestingly, no airport selected "unimportant" or Many of the respondents to the EPA questionnaire (49) "not very important" for any of the criteria options in the sur- also provided the amounts of chemicals applied during the vey, highlighting the challenges and dilemmas faced by the TABLE 2 TYPE OF PDP USED AT U.S. AIRPORTS DURING 2004/2005 WINTER SEASON Size Classification Large Hub Medium Hub Small Hub Non-Hub Chemical/Material (17) (21) (19) (44) Total Airside Urea 4 6 6 14 30 Sodium Formate 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.
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7 TABLE 3 AMOUNT OF DEICERS APPLIED AT THE REPORTING U.S. AIRPORTS DURING THREE WINTER SEASONS 2002/03 2003/04 2004/05 No. No. No. Chemical/Material Airports Amount Airports Amount 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 1 373,185 1 151,118 1 261,887 Fluids (gallons) Propylene Glycol-Based 4 225,800 4 226,200 4 256,537 Fluids (gallons) Note: Data based on a subset of the data from the 2006 EPA questionnaire. airports pertinent to snow and ice control. A European airport cols. The next chapter will discuss the impacts of PDPs on filled in two "other" criteria: (1) impact on asphalt pavement aircraft components. Although corrosion risk and electrical and (2) impact on working environment, both considered conductivity were judged least important compared with the "very important." other factors, the average response was still above "impor- tant." However, their relative importance to airport staff The high use of KAc at airports is consistent with both the implies that any new PDP formulations must not sacrifice general FAA preference to anti-icing practices and its more effectiveness or environmental liability in looking for PDPs benign environmental impact compared with urea and gly- that may be more compatible with aircraft components. 5 Average Importance 4 3 2 1 Effectiveness Environmental Cost Corrosion Electrical Impact Risk Conductivity FIGURE 2 Importance of various criteria considered by airports for PDP selection; bars represent two standard deviations.