Case Study: When Bigger Is Better: Large-Scale Rental Car Facility Uses Innovative Treatment System To Surpass Stormwater Regulations
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Nearly 53,000 people fly in and out of Maryland's Baltimore/Washington International Airport (BWI) daily. The 3,596-acre airport provides both parking for departing passengers and access to thousands of rental cars for arriving passengers. Recently, BWI opened a new 50,000 sq. ft., two-story, 6,000 car parking facility and one-stop carrental mall.
Engineers at Michael Baker Corporation, Alexandria, Va., installed a treatment system for stormwater running off the building's rooftop, the top floor of its 6,000-car parking garage, and facility roadways and auxiliary parking areas. Using a passive, underground filtration system, the engineers met Maryland's stringent water quality requirements while protecting the local environment from pollutants, including sediments, nutrients, heavy metals, and oil and grease.
The Challenge
Located at the end of a runway, the new parking lot and rental car structure could not
interfere with the flight path. To meet this restriction, engineers designed the structure with a
footprint holding 3,000 cars on each of two floors.
Before building the facility, any stormwater runoff reaching the undeveloped site soaked naturally into the ground. Once the land was developed, discharged water ran off the impervious pavement surfaces, making the site susceptible to runoff pollutants from the high volume of cars, buses and the atmospheric deposition from jet exhaust.
EPA requirements established by the NPDES permit program and administered by the Maryland Department of the Environment required stormwater treatment addressing these runoff pollutants.
Maryland water quality regulations require that treatment systems remove 80 percent of total suspended solids (TSS) and 40 percent of total phosphorus from stormwater runoff. In Maryland, phosphorus and nitrogen are keystone pollutants for the Chesapeake Bay because they promote algae blooms that degrade the water quality and the health of the bay.
Click here to download the entire case study in pdf format.
Source: Stormwater360