Sep 06, 2016

Alabama Airport Treats Storm Water at Relocated Taxiway

The Mobile Airport Authority owns and operates the Mobile Downtown Airport, a public use airport located 3 miles south of the central business district of Mobile, Ala. The airport can trace its roots back to Brookley Field, a World War II-era airfield. The airport is the principal component of the Mobile Aeroplex at Brookley, a 1,650-acre industrial complex. Combining the Mobile Airport, east-to-west-coast rail lines, two interstates—I-65 and I-10—and the nearby Mobile Port Authority, the site makes an ideal location for companies that engage in interstate commerce and aviation. 

More than 75 companies lease space at Mobile Aeroplex, including FedEx, Signature Air Support and VT Mobile Aerospace Eng. Most recently, Airbus announced it will build its first North American final assembly line for the A320 family of jetliners at Mobile Aeroplex, making Mobile the home of the company’s first U.S.-based fixed-wing aircraft production facility.

The continued growth of the Mobile Aeroplex necessitated the expansion of the airfield to make it compliant with new Federal Aviation Administration (FAA) standards and more operationally efficient. The expansion includes the construction of the partial parallel taxiway A relocation that will add approximately 3,500 ln ft to the taxiway.

Site drainage was a major challenge during the design phase of the taxiway project. With city storm water runoff regulations restricting any increase in offsite flows from site-related drainage, planners had to review options carefully to ensure compliance with requirements and FAA advisory circulars when addressing drainage for the relocated parallel taxiway.

Detention ponds were not an option, as ponds attract waterfowl and other wildlife that are a safety hazard for aircraft. Therefore, engineers at Michael Baker Jr. Inc. designed eight corrugated metal pipe detention systems using 20,770 ln ft of 60-in.-diameter CORLIX aluminum pipe. Aluminum pipe was selected for this project because of the system's proximity to Mobile Bay, which is a saline environment. The detention system stores storm water underground and releases it slowly over time into Mobile Bay.

Thirteen VortSentry HS storm water treatment systems were installed for pretreatment. These compact storm water treatment systems use helical flow technology to enhance gravitational separation of floating and settling pollutants from storm water. The units will prolong the life of the detention systems and reduce maintenance costs by removing sediment and retaining it in a structure that can be easily maintained.

The project also used 680 ln ft of 48-in. ULTRA FLO pipe to slipline existing 54-in. reinforced concrete pipe that experienced settlement problems at the joints. Due to airfield safety issues, which prevent access into the upstream junction box structure, the pipe had to be pushed upstream from the outlet end.

Installation was completed in phases by H.O. Weaver and Sons Inc. from the fall of 2014 to the winter of 2016.

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