The Problem:

Our team worked on a property in Levittown, NY, where a large sinkhole had developed beneath sections of the concrete walkway and driveway.

The void had formed as smaller gaps underneath the concrete grew larger over time. In some areas, the sinkhole reached approximately 11 feet deep, while another section was about 8 feet deep. The total void was estimated at roughly 6 cubic yards.

Because the concrete walkway and driveway were sitting over the void, simply filling the area from the surface would not provide enough support. The materials had to be properly placed and compacted to stabilize the area.

The Solution:

Our team developed a two-part repair using compacted soil and RCA, followed by mudjacking to fill the remaining voids directly beneath the concrete.

Excavating and Exposing the Sinkhole

We brought approximately 3 yards of soil and 3 yards of recycled concrete aggregate (RCA) to the property.

The team excavated near the concrete walkway to expose the north and south edges of the sinkhole. The edges were then cleared so we could properly access the void and begin filling it.

Filling and Compacting the Sinkhole

The sinkhole was backfilled using soil first.

The material was placed in controlled layers and compacted as the work progressed. A 10-foot tamper was used to help establish a firm base.

RCA was then placed over the compacted soil and continued up to the top of the void.

To help prevent future settlement, the fill material was compacted in approximately 1-foot vertical lifts rather than placing all of the material at once.

Addressing the Void Beneath the Walkway

One challenge was the center of the concrete walkway.

Because the walkway extended too far from the accessible edges of the sinkhole, conventional compacting equipment could not effectively reach the material directly beneath the center of the slab.

Leaving this area unsupported could allow the concrete to settle again.

Mudjacking Concrete Lifting

To address the remaining void beneath the concrete, our team used the mudjacking concrete lifting method.

A commercial-grade, heavy-duty mudjacking pump was used to pump stone slurry grout underneath the concrete slab.

The grout was injected through access points near the edge of the concrete and directed into the open areas beneath the slab.

As the voids filled, the pressure from the stone slurry grout pushed the RCA tightly against the underside of the concrete walkway.

This helped fill areas that could not be reached through conventional compaction.

The Result:

The Levittown project addressed a significant underground void beneath the property’s concrete walkway and driveway.

The repair combined deep backfilling, controlled compaction, and mudjacking to stabilize the area from both below and around the concrete.