Deicing Runoff No Problem for Illinois Airport

• Anticipating new regulations, Chicago Rockford International Airport has become a leader in stormwater glycol treatment.

The Chicago Rockford International Airport (RFD) has always prided itself on staying ahead of the curve. Since 1994, the facility has transformed itself into a “Top 20” cargo airport and is now home to 30 industrial clients, including the largest regional parcel-sorting facility in the UPS System. Throughout its growth, the airport has been determined to prevent negative environmental impacts resulting from aircraft and pavement deicing. Today, RFD is staying ahead of the curve by being a leader in stormwater glycol treatment.

Proximity of the treatment ponds in relation to the new international cargo site for the Rockford, IL, airport near Chicago. [Credit: Brian Thomas Photography, Rockford, IL]

Since UPS opened its regional air hub at the airport, RFD has treated airfield stormwater runoff by removing 1.7 million gallons of glycol before discharging the water to the Rock River. These efforts result in consistently meeting existing general permitting requirements of the U.S. Environmental Protection Agency, as well as Illinois water quality standards. Moreover, RFD's stormwater treatment facility is capable of meeting new EPA regulations anticipated in 2009.

A New Approach

Aircraft and pavement de-icing is a nationwide issue. For the past 16 years, the EPA has issued nationwide general industrial stormwater permits to airports and other point sources of stormwater runoff, covering deicing chemicals as well as other components, under its stormwater regulation program. The program requires permitted industry groups to document and operate under stormwater “best management practices” (BMPs) aligned with EPA's guidance documents and to submit annual reports on their stormwater activities to the EPA. These permits, however, don't specify discharge limits or end-of-pipe requirements. In more recent years, some states have enacted site-specific stormwater permits for airports located within their jurisdictions.

An EPA draft document issued in February 2008 indicated that the agency is considering a new, “mass balance” approach to regulation of aircraft and airfield pavement deicing: accountability for use and tracking of deicing materials; stormwater recovery and treatment; recycling of deicing materials; and an end-of-pipe water quality requirement. If so, RFD is prepared to meet these regulations.

A Cost-Effective Solution

When UPS committed to opening its new regional air hub at RFD in 1993, the airport was determined to prevent negative environmental impacts resulting from aircraft and pavement deicing. As part of its responsibility for the design and construction of the new 26.5-acre apron, consulting engineers Crawford, Murphy & Tilly Inc. developed a cost-effective strategy for managing stormwater runoff containing ethylene or propylene glycol.

Relationship of treatment cells to UPS airport hub in 1994. [Credit: Brian Thomas Photography, Rockford, IL]

At that time, the absence of specific EPA regulations governing aircraft and airfield deicing, a lack of aviation industry prototypes, and limited data on water-quality impacts of glycol treatment approaches posed challenges for the engineers. Nevertheless, system engineers designed a treatment facility based on their experience in the aviation, water and wastewater industries, as well as discussions with the local public wastewater treatment plant personnel and plan review by the Illinois EPA.

The solution involves concentration of deicing procedures on the southern portion of the apron and an independent storm sewer system that directs glycol-containing stormwater runoff to a two-cell retention pond system, where an aerobic treatment system reduces the biochemical oxygen demand (BOD) of glycol-containing stormwater runoff to a level that can be released without negative impact to the Rock River. The system also includes a pump station that transfers runoff from a remote deicing pad to the south apron collection system.

The first pond cell has a capacity of 16 million gallons and covers over five acres. Sixteen 25-hp floating aerators maintain required dissolved oxygen (DO) levels and provide mixing. Nitrogen and phosphorus can be provided as nutrients when required, and the pH of the water can be adjusted through chemical addition to enhance the biological treatment process.

The second pond cell, which was designed for “polishing” the treated water, has a capacity of five million gallons and covers two acres. Both ponds are lined to protect groundwater.

A recirculation pump station not only enables the airport to inject treatment-enhancing chemicals into the retention pond as needed, but also aids in the mixing of the pond contents.

Operational Initiatives

Although the system was originally designed as a flow-through facility, owners have opted to manually close the gates to the river in anticipation of a deicing event to sample and test stormwater runoff. If it meets water quality standards, it's diverted to the river; otherwise, it's captured in the pond. Following the event, operators maintain the gate to the pond in an open position for a period of time to capture residual runoff. After manual sampling and testing shows no residual glycol in the runoff, the gates are switched to allow stormwater without glycol to flow to the river. This volume-saving approach allows the owners to operate the ponds as a single batch for the entire deicing season.

Conclusion

Over the past few years, more than $183 million has been invested in airport and utility infrastructure improvements at RFD – including an additonal wide-body aircraft parking area, which will also drain to the existing treatment ponds, as well as automated gate control and water quality testing – to enable the Rockford, IL, airport to handle further development and remain ahead of the regulatory curve.