Research Projects

Methods for Evaluating Airfield Pavement Deicer Contributions to Airport Stormwater Quality In Reserve

The objective of this research is to develop guidance for airports to quantitatively identify the contributions of airfield pavement deicers to environmentally relevant characteristics of stormwater discharges, such as COD and BOD.

Background (Describe the current situation or problem in the industry, and how your idea would address it.)

The ACRP 02-61 project identified and ranked needs for updating existing ACRP research products related to stormwater management at airports. One of the conclusions of this review was that NPDES stormwater permit compliance requirements increasingly include pavement deicer constituents in stormwater discharges. There are several factors driving this regulatory interest. As controls on aircraft deicing runoff have become more widespread and effective, the relative contribution and influence of pavement deicing runoff, which is typically impractical to collect, on pollutants in stormwater has increased. As an example of why this is important, research by the U.S. Geological Survey and others have concluded that pavement deicers "must be considered to comprehensively evaluate the impact of chemical deicers on aquatic toxicity in water containing airport runoff ." Finally, when the Environmental Protection Agency's 2012 "Effluent Limitations Guidelines and New Source Performance Standards for the Airport Deicing Category" called out the use of urea for airfield pavement deicing as a source of significant pollutants in stormwater discharges from existing airports, it drew regulatory attention to the general use of airfield pavement deicers.

As a result of this increased interest, airports need to know how to properly monitor these constituents in stormwater, and understand how to use monitoring results to assess the contribution of pavement deicing to the total pollutant load. The recently published 2nd Edition of ACRP Report 72: Guidebook for Selecting Methods to Monitor Airport and Aircraft Deicing Materials addressed the first need with the addition of methods for sampling and analyzing formates and acetates, the primary anionic constituents of the most widely used airfield pavement deicers in North America. The need remains for guidance on how to use monitoring and other data to evaluate the contribution of pavement deicers to oxygen demand and aquatic toxicity in airport stormwater discharges.

Airport staff face significant challenges when they attempt to parse out the relative contribution of airfield deicers to these parameters. The sources of Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) cannot be directly identified from their analytical measurements. Typically, the presence and concentrations of other parameters that are unique to particular deicers are used as evidence of the contributions of those chemicals on total BOD and COD measured. With aircraft deicers, this evidence is found in measurements of propylene and ethylene glycols, the freezing point depressants in those products. It's more complicated in the case of airfield pavement deicers because the freezing point depressants contribute both cations (i.e., potassium and sodium ions) for which there may be significant background sources, and anions (acetate and formate ions) which have been shown to degrade very quickly in cold environments compared to the glycols . As a result, measured acetate and formate concentrations in stormwater discharges may not fully reflect the amounts of pavement deicers and their residuals. Although recently published ACRP Report 166: Interpreting Airport Water Monitoring Results provides guidance on interpreting parameters related to aircraft deicers, it does not speak to the described issues regarding pavement deicers.

Requested Allocation (For ACRP Use Only) $350,000

Idea No. 40