Behind the Build: The Hidden Work at Penn’s Landing Park

Ever wondered how you build a park over a highway? Take a behind-the-scenes look at the engineering, materials, and teamwork shaping the new Penn’s Landing Park.

The Basics: What is a Cap?

The new Park at Penn’s Landing is being built over I-95, reconnecting Philadelphia to the Waterfront through a major feat of engineering and construction: a highway cap.

But what is a cap exactly? Simply put, a cap covers a road and provides a steady, supported surface for whatever is on top. This new cap is officially called the CAP, short for Central Access Philadelphia, and is part of a long-term set of enhancements along I-95.

However, while we can define it simply, building a cap over a highway that can support a whole park is no small feat. An array of materials, physics, and people come together to build a cap. Collaborating on a project this large includes PennDOT, FHWA, the City of Philadelphia, DRWC, utilities, inspectors, contractors and subcontractors, fabricators, and suppliers galore!

Photo Credit: Billy Kyle for PennDot

Digging Deeper: How is a Cap Built?

Before construction of the cap began, crews had to demolish a previous highway cap along Front Street over part of I-95. You might think this would make building a new cap easier, but since the new cap is about 4x the size of the previous one, the supports had to be much stronger to hold a heavier structure.

A new vertical support, called a pier, has to be built to hold up the cap. Caissons, or 6-foot-in-diameter casings filled with rebar and concrete, are being installed as part of this Pier 2. Caissons are deep concrete foundations that transfer the weight of heavy structures, such as bridges and tall buildings, to solid rock or stable soil below the surface. The process isn’t quick – each of these caissons takes 1-2 weeks to install.

Usually, when building a highway cap, crews finish all piers and other vertical supports first, then add horizontal support beams on top. But since caissons take time to install, the construction team decided to add beams before the second set of supports was finished.

After the supports are finished and all the beams are installed, the builders will add layers of concrete and fill to create a surface for the bridge deck with troughs that the trees will be planted in and since a new park with real trees and plants need material they can grow in, 3-4 layers of different types of fill and soil will be used to allow for root health and water drainage to maintain them.

The new park will also extend down towards the Waterfront, past the end of the cap. To create a smooth transition, the construction team will add 20-30 feet of fill sloping down toward the Waterfront. Inside the fill, the team will install supports and utilities for the buildings above. From start to finish, it is a massive project.

It’s in the Details: What Goes into the Build?

We checked in with Frank Bonito, Construction Manager on the CAP, about the construction process, materials, and people working on the project.

How does weather affect the construction schedule?
The construction schedule already factors in weather, including limits on when materials like concrete and asphalt can be used safely. During extreme weather like in early 2026, contractors may need extra steps to keep work moving. In this case, the contractor poured concrete, but they needed to wrap the area and heat it. Adjustments like that can require additional labor, materials, and inspection. Temperature also affects steel beams, so engineers and contractors account for expansion and contraction when installing them. 

There’s soil and fill; what is the fill made of?
The fill is a recycled foam glass aggregate. It’s surprisingly light; it feels like pumice to touch. The same type of fill was used to create a temporary fix after the 2023 I-95 bridge collapse, helping stabilize the new section while permanent structures were completed.

Do you have a favorite detail about this construction project?
Usually, the walls that help support a cap have a steel-like finish. However, the builders wanted something that felt more like it fit the neighborhood. They found a way to press a wood pattern into the surface to give it a different texture. It matches the theme of timber used in other places throughout the park, like the pavilion

How many people are working on the CAP at once? How many different specialty subcontractors are needed
It depends on what needs to be done; sometimes there might be 30 people onsite, but other times, there could be 50 or 60. PennDOT has one prime contractor that employs 59 subcontractors. Subcontractors include specialized contractors, rental companies, fabricators, demolition firms, tree suppliers, etc.

Site Evolution: How does the CAP support the Park?

The CAP supports the park’s structure, function, and layers, both visible and invisible to the park visitor. 

One clear example is the crossbar diaphragms that hold up the park, which were designed with special trenches. Some of these trenches provide space for the root balls of the over 400 trees that will be planted, allowing them room to grow and helping them stay steady and upright as they mature. Other trenches have drainage for water features, and some will have room for electricity and other utilities to keep the cafe and buildings functional.

Photo Credit: Billy Kyle for PennDot

From the foundations below to the future park above, every layer of the CAP is helping reconnect Philadelphia to its Waterfront for generations to come.

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PennDOT is replacing and expanding the covered section of I-95 at Penn’s Landing along the Waterfront in Center City Philadelphia under the department’s $329 million I-95/CAP project. The two main components of this project are the construction of a new 11.5-acre Park at Penn’s Landing and a new South Street pedestrian bridge. Review the latest renderings of the new Park at Penn’s Landing.