On game days in South Philadelphia, thousands of people park, tailgate, and file into Lincoln Financial Field without a second thought about the ground under their cars, the same ground that’s doing something most of them will never notice. Beneath one stadium-district parking lot sits a stormwater detention basin with a capacity of well over 350,000 cubic feet, quietly holding back the rain that used to overwhelm the city’s sewers.
That basin is the Darien Crossing project, and it is a working example of how a dense, paved-over city can solve an old water problem without giving up the land it needs. For RES, it is also proof that green infrastructure and everyday urban life can share the same footprint.
The site began as a food warehouse, built in the 1950s and 60s and used until the end of the 1990s. After that, it sat vacant for two decades, a large empty structure the city wanted back on the tax rolls and back in service for the community. The opportunity that emerged was not another building; It was water storage.
Philadelphia, like many older American cities, carries a particular plumbing burden. Across much of the city, the sanitary and storm sewers are combined into a single system. Everything that falls from the sky mixes with everything that drains from homes and businesses, and all of it is meant to be treated before it reaches the rivers. When a big storm overwhelms that system, the treatment plants have no choice but to release untreated water into nearby waterways. Those combined sewer overflows are a serious water quality problem, and they are exactly what the Darien Crossing basin was built to reduce.
The location made the problem worse and the solution more valuable. The stadium district is one of the most densely populated and heavily paved parts of Pennsylvania, a landscape of parking lots, buildings, and other hard surfaces that rain cannot soak through. Water that should recharge the ground instead rushes across pavement straight into the sewer. A site this impaired is precisely where a stormwater retrofit does the most good.
The design is straightforward in concept and invisible in practice. RES removed the northern third of the old warehouse and excavated the parcel in phases, working within the lot's tight dimensions. In place of the demolished section, a large subsurface detention basin was installed. The existing pipes that drained the surrounding parking lots were connected to it, so that after a heavy rain, the basin collects the runoff, holds it for a set period, and then slowly releases it into the combined sewer system rather than all at once.
That slow release is the whole point. By detaining the surge and metering it out, the basin keeps peak flows from overwhelming the treatment plant, which is what triggers an overflow in the first place. Once the landscaping and paving were finished, the surface returned to work as a parking lot. As the project team put it, the public parks on top of a basin holding hundreds of thousands of cubic feet of stormwater, and have no idea it is there.
Darien Crossing was funded through the Greened Acre Retrofit Program, a part of Philadelphia’s Green City, Clean Waters plan adopted in 2011. The idea behind Green City, Clean Waters is to use green infrastructure rather than just bigger pipes and tanks to reduce the volume of stormwater entering the combined sewer system and limit overflows. The Greened Acre grant is a flexible tool that leverages private resources and innovation to solve a public infrastructure problem for the city’s water department.
What makes that model work is the partnership behind it. The Philadelphia Industrial Development Corporation owned the parcel. The Philadelphia Water Department managed the grant and the stormwater billing program that gives property owners a reason to build these systems. The Greater Philadelphia Chamber of Commerce helped connect the effort to other businesses, and the sports teams and the thousands of fans who use the district every game day all had a stake in the outcome. Once the partners saw the shared benefit, the project moved from concept to construction.
The economics matter too. RES holds a long-term lease to operate and maintain the facility for decades after construction, and the property stakeholders, including PIDC and the Philadelphia Phillies, see meaningfully reduced stormwater fees as a result of the retrofit. The land does two jobs at once: it stores stormwater below and serves the district above.
The reason Darien Crossing matters beyond its own block is that its problem is common. Historic cities across the United States struggle with aging, overtaxed stormwater infrastructure, and a shortage of open land to fix it. What Philadelphia did was spend real time building a policy and a grant program that actually works for the developers doing the work. What RES did was turn that policy into a built, functioning system by collaborating with the water department, the development corporation, and talented local contractors to deconstruct the site, execute the design, and construct the solution.
That combination, workable public policy plus private execution on a difficult site, is what makes the project repeatable. It is a template that other older cities can study when they face the same walls of pavement and the same overwhelmed sewers.
There is a human measure of it as well. One member of the team described what the project means to him in plain terms: he will bring his kids to the lot, tell them he built this, and know it will be there longer than he will. Good infrastructure tends to be the kind nobody notices. This one will keep working quietly under a parking lot for a long time, which is exactly what it was designed to do.