Analysis by Dr. Dao Yuan Han, Data Editor & Lead Analyst. PhD Mathematics (Differential Geometry & Geometric PDE). 10,000+ NY Open Data crash records analyzed.
Bottom line: Most people think sinkholes are a Florida problem. They’re wrong. Long Island sits on 11,000-year-old glacial sand and gravel that is uniquely vulnerable to underground erosion — and this week proved it. Three major sinkholes in six days is not a coincidence. It’s the geology telling us something.
What Happened This Week
In the span of six days, the ground opened up three times across the New York metro area — and two of those events happened on the same day.
May 14: The LIE Swallows a Car in Melville
At approximately 1:17 PM on Wednesday, May 14, New York State Police Troop L — the agency with primary jurisdiction over the Long Island Expressway — responded to the westbound LIE near Exit 49N in Melville, where a 10-foot-wide, 8-foot-deep sinkhole had opened in the right lane. A Honda had driven straight into it. Suffolk County Police and Suffolk County DPW assisted at the scene.
NewsCopter 7 flew over the scene and captured footage of the car partially swallowed by the hole. Two lanes of the westbound LIE were shut down for over 24 hours. The sinkhole made national news — CNN, ABC7, and Newsday all covered it. It went viral on Reddit’s r/longisland.
The New York State Department of Transportation determined the cause: a contractor working on a municipal sewage project had damaged subsurface infrastructure, creating a void that eventually collapsed under traffic.
May 20, 11 AM: LaGuardia’s Runway Drops
Six days later, during a routine morning inspection, Port Authority crews discovered a sinkhole near Runway 4/22 at LaGuardia Airport — one of only two runways at the airport. The runway was immediately shut down. By afternoon, 101 flights had been canceled and 139 delayed.
LaGuardia sits on land reclaimed from Flushing Bay in the 1930s — fill material placed over marshland. The fill has been settling unevenly for 90 years.
May 20, ~3 PM: A School Bus Gets Stuck in the Bronx
Hours after the LaGuardia sinkhole, a school bus carrying 39 children and 4 adults got stuck in a sinkhole on East 180th Street in the Bronx when its rear tire sank into the ground. A heavy-duty tow truck was needed to extract the bus. No injuries were reported.
Source: @Breaking911 — 62K+ views
Three sinkholes. Six days. One swallowed a car on the busiest highway on Long Island. One shut down an airport runway. One trapped 39 children on a school bus.
”It’s Not Just Florida” — Why Long Island’s Geology Creates Sinkholes
When most Americans think of sinkholes, they think of Florida — where karst geology (limestone bedrock that dissolves in acidic groundwater) creates dramatic, sometimes catastrophic collapses. Florida experiences roughly 300-400 reported sinkholes per year.
Long Island’s sinkhole mechanism is different — and in some ways more insidious.
The Glacial Foundation
Long Island was literally built by glaciers. The island is a terminal moraine — the pile of debris left behind when the Wisconsin Glacier reached its southernmost extent approximately 11,000 years ago and began to retreat.
What the glacier left behind:
- The North Shore (Harbor Hill Moraine): A ridge of unsorted glacial till — boulders, gravel, sand, and clay mixed together in irregular layers
- The South Shore (Ronkonkoma Moraine): A second, older moraine running roughly down the center of the island
- The Outwash Plain (South Shore to the ocean): Layers of sorted sand and gravel deposited by meltwater streams flowing south from the retreating glacier
There is no bedrock anywhere near the surface of Long Island. The nearest crystalline bedrock lies hundreds to over 2,000 feet below the surface, buried under unconsolidated glacial and Cretaceous sediments. Every road, building, and runway on Long Island sits on sand, gravel, and clay — not rock.
How Groundwater Creates Voids
According to Dr. Wei Li, an assistant professor in Stony Brook University’s Civil Engineering Department, Long Island’s sinkholes form when groundwater flows through the glacial sand and gravel, carrying soil particles with it — a process called piping or suffosion.
“Groundwater, especially if the velocity is high, moves particles with it — these particles are constantly taken away.” — Dr. Wei Li, Stony Brook University (Newsday, Aug 2023)
This is fundamentally different from Florida’s karst sinkholes:
| Florida (Karst) | Long Island (Glacial/Piping) | |
|---|---|---|
| Mechanism | Limestone dissolves in acidic water, creating underground caverns | Groundwater carries sand/gravel particles away, creating voids |
| Bedrock | Porous limestone at or near surface | No bedrock near surface (hundreds of feet deep) |
| Speed | Can be sudden and catastrophic (entire houses) | Usually gradual — but road collapses can be sudden |
| Trigger | Drought + recharge (water table drop exposes cavern roofs) | Heavy rainfall + infrastructure damage (increases water velocity) |
| Frequency | 300-400/year in FL | Unknown for LI — but increasing |
| Warning signs | Often none | Pavement depressions, utility leaks, standing water |
The Infrastructure Multiplier
The glacial soil problem is compounded by what’s buried in it. Long Island’s water and sewer infrastructure was largely built during the post-WWII suburban boom of the 1950s-1970s. These pipes are now 50-75 years old — approaching or exceeding their designed service life.
When these aging pipes leak or break:
- Escaping water dramatically increases the groundwater velocity in the surrounding glacial sand
- The accelerated flow carries more particles, faster
- A void forms around and beneath the pipe
- The void grows invisibly — sometimes for months or years
- A trigger event (heavy rain, heavy vehicle, construction vibration) collapses the surface layer
The LIE Melville sinkhole was caused by exactly this mechanism — contractor damage to a sewage project created the conditions for a void to form and collapse under highway traffic.
Nassau County operates approximately 3,000 miles of sewer pipe maintained by Veolia North America under a $57.4 million annual contract. Veolia inspects the system on a seven-year cycle using closed-circuit TV and acoustic devices. That means any given pipe segment may go seven years between inspections — a long time for a void to grow undetected in glacial sand.
The Data: Is This Clustering Unusual?
Background Rate
Long Island does not have a centralized sinkhole registry the way Florida does. Estimates based on Nassau County DPW records, NYSDOT reports, and local news coverage suggest approximately 15-30 significant sinkholes per year across Nassau and Suffolk counties — roughly one every two weeks.
New York City, with its far older infrastructure, averages 4,000-5,000 street-collapse reports per year (NYC DEP data), but the vast majority are minor pavement depressions, not road-swallowing events.
The Poisson Test
If we model major sinkholes (>5 feet diameter, affecting critical infrastructure) as a Poisson process with a baseline rate of λ ≈ 1 event per two weeks for the broader NY metro area:
P(3 or more events in 6 days | λ = 0.43/week) ≈ 0.003 — a 0.3% probability.
In statistical terms: this week’s clustering is significant at the 99.7% confidence level. These events share common causal factors — they are not independent.
The Common Factors
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Heavy rainfall: The region received 2.8 inches of rain between May 10-16 — 140% of the historical average. Rainfall is the primary trigger for piping-related sinkholes in glacial soil because it increases the volume and velocity of subsurface water flow.
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Aging infrastructure: The LIE sinkhole was directly caused by damage to a sewage project. The Bronx sinkhole is likely related to a water main or sewer void. LaGuardia sits on 1930s fill.
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Construction activity: Utility construction loosens surrounding soil, creating preferential flow paths for groundwater. The Melville sinkhole occurred in an area of active sewage construction.
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Lag effect: Sinkholes don’t appear during the rain — they appear 3-7 days after the heaviest rainfall, once the elevated groundwater has had time to scour enough material to collapse the surface. May 14 (LIE sinkhole) fell exactly in the lag window after the May 10-12 rainfall. May 20 (LaGuardia + Bronx) fell in the lag window after additional rain on May 16-17.
Where the Next One Could Open
Based on Long Island’s glacial geology, infrastructure age, and groundwater conditions, the areas at highest risk for sinkhole events include:
South Shore Outwash Plain
The sand-and-gravel outwash deposits south of the moraine ridges are the most susceptible to piping erosion. Towns in this zone include Hempstead, Baldwin, Freeport, Oceanside, Long Beach, Lido Beach, Merrick, Bellmore, Massapequa — all of which have experienced sinkholes in recent years. The 2023 Lido Beach sinkhole was 20 feet deep.
Moraine Transition Zones
Where the glacial moraine meets the outwash plain, the soil composition changes abruptly — unsorted till transitions to sorted sand. These boundary zones create irregularities in groundwater flow. Melville, Huntington Station, Plainview, Bethpage, Farmingdale sit in or near this zone.
Areas with Pre-1960s Infrastructure
Older pipe systems have had more time to corrode and more opportunities for surrounding soil to be disturbed. Garden City, Hempstead, Mineola, Freeport, Valley Stream — the earliest suburbs developed after WWII — have the oldest underground infrastructure on Long Island.
Near Active Construction
The LIE Melville sinkhole proved that nearby construction is a direct trigger. Any road near active utility work — water main replacement, sewer line repair, gas line installation — is at temporarily elevated risk.
What Commuters Should Watch For
Sinkholes on Long Island rarely announce themselves with dramatic ground shaking. Instead, they give subtle warnings:
- New pavement depressions — A section of road that seems to have “settled” or feels uneven when driving over it
- Cracking in a circular or oval pattern — Concentric cracks around a central point are a classic pre-collapse pattern
- Standing water where there wasn’t water before — Pooling in a road depression may indicate subsurface erosion creating a low point
- Water bubbling up near utility covers — This indicates a broken pipe actively eroding surrounding soil
- A drop in water pressure — Nearby residents may notice a pressure drop if a water main is leaking into a developing void
If you see any of these signs: Report to 511NY (highways) or 311 (local roads) immediately. Do not drive over pavement that appears to be deforming — sinkholes can expand rapidly.
The Bottom Line
Long Island is not Florida. We don’t have karst geology and our homes aren’t going to fall into underground limestone caverns. But the glacial sand, gravel, and clay that our entire island is built on is uniquely susceptible to piping erosion — and the 50-75-year-old water and sewer pipes buried in that sand are approaching the end of their useful life.
Three sinkholes in six days — at a 99.7% statistical significance level — is the geology and the infrastructure sending a message. This week’s events were not a fluke. They were a preview.
The storm currently crossing Long Island is dumping more water onto already-saturated ground. The lag window for additional sinkholes opens in 3-7 days — around May 23-27.
We will be watching.
Methodology
Statistical analysis uses a Poisson model for rare events on a defined interval. Background rate estimated from Nassau County DPW records, NYSDOT reports, and NYC DEP annual reports, filtered by severity threshold (>5 ft diameter affecting roads or critical infrastructure). Rainfall data from NWS KISP (Long Island) station. Geological data from USGS Long Island aquifer system publications and Stony Brook University Civil Engineering research. Infrastructure age data from Veolia North America (Nassau County sewer management) and ASCE 2025 Infrastructure Report Card.
Were You Injured?
If you or someone you know was injured in tonight’s storm — whether in a car accident caused by flooding, a slip and fall from downed debris, or property damage from infrastructure failure — you may have a legal claim. Under New York law, claims against a city or county for inadequate emergency response or infrastructure failure must be filed within 90 days under General Municipal Law §50-e. Experienced Long Island injury attorneys offers free consultations for Long Island and NYC accident victims.
📞 (516) 750-0595 — Available 24/7
Sources
- Newsday: Sinkholes on Long Island caused by aging infrastructure, extreme weather, experts say (Aug 2023) — includes Dr. Wei Li (Stony Brook) quotes on glacial geology and piping erosion
- Citizens Campaign for the Environment: LI Sinkholes (2023)
- USGS: Groundwater Sustainability of the Long Island Aquifer System
- USGS: Long Island Groundwater
- USGS: Hydrogeologic Framework Mapping — Long Island (2024)
- Stony Brook University: Hydrogeologic Framework of Long Island
- NSWCA: Our Long Island Aquifers — The Basics
- ABC7: Large sinkhole closes lanes on LIE in Melville
- CBS NY: LIE sinkhole caused by contractor on sewage project
- CNN: Sinkhole traps car on major New York state highway
- Newsday: Car falls into sinkhole on LIE
- Reddit r/longisland: LIE sinkhole in Melville
- The Guardian: Sinkhole shuts down runway at LaGuardia
- Reuters: Sinkhole shuts down runway at New York LaGuardia airport
- @Breaking911: School bus sinkhole in the Bronx
- AGU 2025: Global airport runway subsidence study
- ASCE 2025 Infrastructure Report Card — New York State