Managing Airfield Stormwater

Over 42 square-miles of watershed drainage area flows through or directly adjacent to the Quad City International Airport (QCIA), which is bounded by the Rock River, two major tributaries, and a bluff rising over 100 feet. It’s not surprising that stormwater management can be a challenge in such a setting as is the need to mitigate conditions that are attractive to wildlife. All of this made it critically important to have a comprehensive and value-driven Master Drainage Study to guide the design and permitting of future stormwater management projects.

Crawford, Murphy & Tilly (CMT) was given the responsibility to complete the study, based on our familiarity with the airport and our talented team of drainage professionals. The comprehensive study of existing site conditions included an inventory of drainage facilities, floodplains and wetlands, extensive modeling of storm sewer and floodplain, a geotechnical investigation program and an identification of known drainage issues. The Airport Layout Plan (ALP) was evaluated to identify impacts to the existing drainage system, quantify the amount of required stormwater detention and assess the feasibility of these stormwater improvements in an aviation environment. CMT collaborated with QCIA and Rock Island County, the local stormwater permitting agency, to develop a fee-in-lieu stormwater detention agreement that allows future development to comply with the County Stormwater Ordinance without constructing detention basins that would attract wildlife.

Additional key outcomes from the study included a determination of an airport base-flood elevation that will serve as the basis for flood protection for future development, recommended projects intended to reduce open water wildlife attractants, and suggested actions for responding to future regulatory standard updates.