Sinkhole Causes & Repair Strategies Explained

A sinkhole left one Texas community with a massive repair bill after it caused significant damage to the municipality’s main sewer line.

According to Community Impact Newspapers, Southern Montgomery County Municipal Utility District (SMC MUD) discovered the sinkhole in the City of Oak Ridge North, Texas. On August 12, Oak Ridge North City Council approved a $45,242 expense to cover the cost of the emergency repairs required to prevent loss of service to city residents.

“There was about 20 linear feet of ductile iron pipe, and a manhole where we had a pretty significant sinkhole that was identified,” said Kim Wright, general manager of SMC MUD. “We have some significant deterioration in this area, and so we have defined a project for this next fiscal year to start addressing this area. It’s approximately just over 1,700 linear feet of ductile iron pipe in this area, and about 14 manholes that we’re looking at rehabbing.”

According to Community Impact’s article, the funding approved by Oak Ridge North’s city council in August will go toward a $138,920 engineering study performed on behalf of SMC MUD to determine the best course of action for repairs.

Wright told the publication that she will return to provide the city’s expenses for the actual reconstruction of the pipeline once a construction bid is completed. This cost will be shared with the other municipalities which are serviced by SMC MUD. Wright said that the total construction estimate is roughly $828,000.

Sinkholes present an often overlooked but significant threat to our infrastructure, especially to buried utilities like water mains, gas pipelines, electrical conduits, and telecommunications cables.

As urban centers expand and aging infrastructure faces new challenges, understanding sinkholes’ impact and how to mitigate their effects is crucial.

Common Causes of Sinkholes

Sinkholes form due to natural and human-induced factors that destabilize the ground beneath the surface, creating a cavity that eventually collapses. Understanding these causes is the first step in developing effective strategies to protect buried utilities.

1. Natural Geological Processes

• Karst Topography: One of the most prevalent natural causes of sinkholes is the dissolution of soluble bedrock, such as limestone, gypsum, or salt, over time. This process, known as karst topography, occurs as groundwater moves through the rock, slowly dissolving it and creating underground voids. Eventually, the surface layer can collapse, creating a sinkhole. Areas with significant karst landscapes, such as Florida and parts of the Midwest, are particularly vulnerable
• Heavy Rainfall and Flooding: When areas receive heavy rainfall or experience flooding, soil and rock layers can become saturated. Excessive water can erode these layers, weakening their structure and increasing the likelihood of a sinkhole. Regions prone to tropical storms, hurricanes, or monsoons are at a higher risk of weather-induced sinkholes
• Drought: In a counterintuitive twist, drought conditions can also lead to sinkholes. As water levels drop, underground voids that were once supported by water pressure can collapse, causing the ground above to sink

2. Human-Induced Causes

• Water Infrastructure Leaks: Aging water infrastructure, especially in older cities, is prone to leaks that can erode surrounding soil over time, leading to sinkholes. Leaking water mains or sewer lines gradually wash away soil, creating voids that eventually cause the ground to collapse
• Construction and Excavation: Construction activities that involve heavy machinery or deep excavation can destabilize nearby soil, especially in areas with loose or sandy ground. Blasting, pile driving, or removing large volumes of earth can cause localized sinkholes by disturbing the natural equilibrium of the soil
• Mining and Drilling: Extractive activities, such as mining and drilling for oil or natural gas, can contribute to sinkholes. By removing subsurface materials, these activities leave behind voids that can collapse over time. Even abandoned mines, which are sometimes overlooked, can pose a long-term sinkhole risk if not properly managed

Prevention Strategies to Minimize Sinkhole Risk

While sinkholes are challenging to prevent entirely, especially in high-risk regions, certain strategies can mitigate their occurrence and limit the associated risks to infrastructure.

1. Regular Infrastructure Inspections and Maintenance: Conducting frequent inspections of underground utilities, especially older water and sewage systems, is essential to identify leaks or weaknesses that could lead to sinkholes. Utility companies often use advanced technologies, like ground-penetrating radar (GPR) and acoustic leak detection, to detect anomalies beneath the surface. Early detection allows for prompt repairs, preventing small issues from escalating into full-blown sinkhole crises.
2. Improving Drainage and Water Management: Adequate drainage systems help reduce soil saturation during heavy rainfalls, which is critical in minimizing sinkhole risk. Installing systems that channel water away from vulnerable areas and maintain groundwater levels can prevent destabilizing soil erosion. In urban areas, replacing impervious surfaces like concrete with permeable materials can reduce runoff and allow better water absorption into the ground.
3. Responsible Construction Practices: In construction projects, soil studies and geotechnical surveys are crucial to assess potential sinkhole risks before breaking ground. Building on stable ground and avoiding construction in high-risk karst areas, when possible, can significantly reduce sinkhole formation. Additionally, reinforcing underground utility installations with protective layers, such as concrete or other materials, can help maintain stability.
4. Policy and Zoning Regulations: City planners and policymakers play a role in minimizing sinkhole risk by enforcing regulations that prevent construction in high-risk areas. Zoning regulations can restrict development in regions with significant karst topography or where there is a history of sinkholes. In regions where development must occur in vulnerable areas, stricter building codes and mitigation requirements can provide additional safeguards.

Protecting Buried Utilities from Sinkhole Damage

For utilities buried beneath the ground, sinkholes represent a critical vulnerability. Fortunately, there are strategies and technologies that can offer some level of protection.

1. Robust Utility Installation Standards: The materials and methods used to bury utilities impact their resilience to ground movement. Installing pipes, cables, and conduits in a protective casing, such as concrete, helps shield them from soil shifts caused by sinkholes. Reinforced materials can also absorb some of the pressure created by a collapsing void, reducing the likelihood of complete failure.
2. Utility Placement and Depth Considerations: When installing new utilities, carefully selecting the depth and location can reduce the risk of damage from sinkholes. In areas with known sinkhole risks, utilities should be buried deeper or rerouted to more stable regions. Situating utilities away from water-logged soil or natural drainage paths also helps protect them from soil erosion.
3. Monitoring and Detection Systems: Installing sensors along utility lines can help detect early signs of potential sinkhole formation. Ground-penetrating radar (GPR), for example, can detect voids beneath the surface, allowing utility companies to act proactively. Advanced warning systems can alert crews to shifts in the ground, enabling quick intervention to prevent or mitigate sinkhole damage.
4. Relocating Critical Utilities: In regions with a high incidence of sinkholes, it may be necessary to relocate critical infrastructure to minimize damage risks. In such cases, utility companies can assess the most vulnerable utilities and move them to safer areas or use above-ground installations if feasible. While expensive, relocating essential utilities reduces the long-term risks and costs associated with frequent sinkhole damage.

A Proactive Approach to Sinkhole Management

With a combination of technology, infrastructure investment, and regulatory planning, it’s possible to reduce the impact of sinkholes on buried utilities, ensuring this infrastructure remains secure despite the challenges posed by these geological threats.

GPRS is proud to offer a comprehensive suite of subsurface damage prevention, existing conditions documentation, and construction & facilities project management services and products designed to keep you on time, on budget, and safe. Our 99.8%+ accurate utility locating services help you find, and map buried infrastructure, ensuring you know where you can and can’t safely dig during excavation projects and helping you prevent sinkholes by identifying trouble areas where voids may be forming underground.

Our Video Pipe Inspection services utilize remote-controlled sewer inspection rovers and push-fed sewer scopes equipped with CCTV cameras and traceable instrument probes, so we can inspect your buried sewer lines for defects and damage at the same time we’re mapping these critical utilities. And using acoustic leak detectors and leak detection (also known as leak noise) correlators, we can pinpoint leaks in buried water lines that, if left untreated, could deteriorate the surrounding soil and cause sinkholes.

All this crucial infrastructure data needs to be at your fingertips when and where you need it. That’s why GPRS created SiteMap^® (patent pending) a facility & project management application that provides existing conditions documentation to protect your assets and people. Easily, yet securely accessible 24/7 via computer, tablet, or smartphone, SiteMap^® ensures you and your team have the accurate, complete data you need to plan, design, manage, dig, and ultimately build better.

GPRS’ SiteMap^® team members are currently scheduling live, personal SiteMap^® demos. Click below to schedule your demo today!

Frequently Asked Questions

Can ground penetrating radar scanning determine the exact size of a subsurface void cavity?

No. GPR scanners can identify the area where a void is likely occurring, and the boundaries of this space. It cannot measure the void’s depth.

How far into the ground can GPR penetrate?

It depends on the application and external factors.

For precision concrete scanning, GPR can typically penetrate 18”-24” into the ground. When locating buried utilities on grass, asphalt, or concrete, the antenna can generally penetrate up to 8’, but this can vary greatly depending on site conditions.

To compensate for GPR’s limitations, GPRS’ SIM-certified Project Managers are specially trained to utilize complimentary technology such as electromagnetic (EM) locating.