Case Study

How a Hidden Pipe Failure Created a Sinkhole and Pond Erosion at a Commercial Property in Orange City, Fla.

Orange City, Fla

Commercial

Stormwater Repairs & Rehabilitations

Identifying the Stormwater Failure

When a sinkhole opened in a parking lot drive aisle at a commercial shopping center, the property’s management team called AQUALIS to find out what was happening underground. An underground inspection camera traced the cause to a damaged stormwater pipe and a separate pipe collapse near the property’s retention pond, two problems that turned out to be connected. AQUALIS replaced the failed pipe sections, repaired the pavement and pond slopes and lined the rest of the pipe system to prevent the same kind of failure from happening again elsewhere along its length.

How Stormwater Systems Work

Most commercial properties rely on a stormwater system, a network of underground pipes and catch basins that collect rain runoff from parking lots and rooftops and carries it to a retention pond. The pond temporarily holds the water and releases it slowly, which keeps the property from flooding and keeps fast-moving runoff from washing sediment and pollutants into nearby waterways.

That system only works as long as the pipe stays structurally sound. Pipe sections are joined together end to end, and over time those joints can separate slightly, especially if the ground around them shifts or settles. Pipe is also installed at a certain depth, sometimes below the water table, the underground level at which soil is naturally saturated with groundwater. A pipe sitting below or near the water table is under constant outside pressure, and any joint or crack becomes an entry point for that groundwater, along with the sand and sediment it carries, to seep in.

Once sediment gets into a pipe, it settles in low spots and starts to build up, the same way silt builds up in a riverbed. That buildup reduces the pipe’s capacity, resulting in less space for water to move through the system which causes flooding. A pipe running at reduced capacity backs up faster, holds standing water longer and puts more pressure on its own walls and joints every time it rains hard, which makes the original damage worse and speeds up future failures.

How One Failure Leads to Another

This particular failure was forming in the loading dock area, a part of the property most people never think about because it isn’t customer facing. Loading docks take a beating from delivery trucks day in and day out, and the cracking, settling and shallow depressions that come with that kind of heavy traffic are common enough that they often get written off as ordinary wear and tear. That assumption is part of what allowed this problem to progress as far as it did. A few cracks in a back service drive rarely raise alarms the way the same damage would in a customer parking area, so the pavement can look like it just needs a patch while the real damage, a stormwater pipe losing its structural integrity, is happening completely out of sight underneath it.

That is what investigators found at this property. An inspection camera sent through roughly 1,000 feet of pipe found water and sediment leaking in at multiple joints, evidence that the pipe had separated and was letting groundwater migrate in and out. One stretch of pipe had sagged enough that it could no longer drain properly, and sediment had collected in the low point, choking off flow. As soil around the leaking joints slowly washed into the pipe, it left a void in the ground above, and that void eventually gave way under the weight of the parking lot pavement, creating the sinkhole. About 56 feet of pipe near the sinkhole could not even be inspected because sediment and standing water were too deep for the camera to pass through.

A second, related problem turned up at the retention pond. The inlet pipe leading into the pond changed materials partway along its run, transitioning from concrete pipe to corrugated metal pipe, and that metal section had corroded and collapsed. The same process that created the sinkhole played out again here: once the pipe lost its shape, the soil packed around and above it lost its support, and the pond’s slope began sliding into the void left behind. That is why the erosion on the pond bank was not a separate issue from the sinkhole. Both were symptoms of the same underlying cause, a stormwater pipe network that had lost structural integrity and capacity in more than one place.

Addressing the Root Cause of the Failure

AQUALIS approached the repair in two phases, and neither one was as simple as digging a hole and dropping in a new piece of pipe. In phase one, crews cut out the damaged asphalt and curb above the sinkhole and excavated down to the pipe. Because that excavation went deeper than 5 feet, crews installed a trench box, a steel shoring structure that holds the trench walls apart so workers can safely get in and out without risking a cave-in. Groundwater seeped into the open trench almost as fast as it could be removed, so a bypass pumping setup ran for the duration of the dig, keeping groundwater out of the work area while rerouting stormwater around the section of pipe that was taken offline, so the rest of the system kept draining normally while the repair was underway.

Once the trench was stable and dry enough to work in safely, crews removed 60 feet of damaged pipe, installed new pipe in its place and backfilled in layers to keep it properly seated. Filling and compacting the trench was only half the job. The entire section of pavement above it then had to be rebuilt from the ground up, new curb, a new sub-base and a full repave of that stretch of the loading dock, rather than a simple patch over the trench line. A nearby section of cracked concrete around a catch basin was also cut out, repoured and finished.

At the retention pond, crews dewatered the work area, removed the collapsed metal pipe and replaced it with 40 feet of new concrete pipe, a stronger, longer-lasting material better suited to wet, below-grade conditions. They then repaired the eroded slope, pulling washed-out soil back into place, adding fill where needed and covering the bank with sod to hold the soil once it was back at grade.

With the damaged sections replaced and the slopes stabilized, AQUALIS moved into phase two, lining the rest of the pipe system. Rather than digging up the entire 735 feet of pipe, crews used a trenchless lining process. A fiber liner soaked in resin was pulled through the existing pipe and cured in place with steam, creating a smooth, seamless layer inside the old pipe that seals off cracks, gaps and leaking joints along its full length, not just the sections that had already failed. The relined pipe restores the system’s original capacity and keeps groundwater and sediment from finding a new way in, which is what prevents this kind of damage from resurfacing somewhere else down the line. A final camera inspection confirmed every problem area had been addressed before the crew left the site.

The completed repairs gave the property a stormwater system built to handle heavy rain for years to come, with minimal disruption to daily operations during the work. By identifying both the visible damage and the underground cause connecting it, AQUALIS delivered a long-term fix instead of a temporary patch, protecting the property, its tenants and the surrounding community from further sinkholes or pond failure.

How to Avoid This in the Future

Problems like this rarely happen all at once. They build slowly, joint by joint and inch of sediment by inch of sediment, often for years before they surface as a sinkhole or a collapsed pipe. That means most of this kind of damage is preventable with the right maintenance schedule.

Routine camera inspections are the most effective tool available, because they allow visual into the pipe before a small joint separation turns into the kind of erosion that undermines a parking lot or a pond bank. Inspecting a stormwater system every few years, or after any major storm, can catch sediment buildup and joint damage early, while the fix is still a cleaning or a spot repair rather than a full excavation.

Retention ponds and the pipes that feed them need their own routine of upkeep as well. Pond banks should be checked regularly for erosion, especially around inlet and outlet pipes, since a slope that starts sliding is often a sign that the pipe beneath it has already lost its shape. Clearing accumulated sediment from catch basins and pipe low points on a set schedule keeps the system’s capacity where it needs to be, so it can move water as fast as it arrives during a storm instead of backing up and adding pressure to already weak spots.

Property owners who schedule preventative maintenance, rather than waiting for a visible failure, typically spend far less over the life of the system. A camera inspection and a sediment cleanout cost a fraction of an excavation, pipe replacement and pond repair, and they catch problems while the pipe is still structurally sound enough to fix without disrupting the property above it.