The Anderson Dam tunnel project recently achieved a significant milestone, showcasing the effectiveness of micro-tunnel boring in the process.

In late 2024, Valley Water completed the final segment of a 1,736-foot tunnel next to the Santa Clara County dam—the largest of the 10 reservoirs in the Santa Clara Valley Water District. According to an article in Underground Infrastructure, this marks a major step toward the agency’s goal of improving water release capabilities during emergencies.

For the last 347 feet of the tunnel, crews used a specialized micro-tunnel boring machine (MTBM). Underground Infrastructure reported that the team guided the machine 30 feet below the reservoir’s surface. Once the boring was finished, divers and construction crews carefully extracted the machine from the tunnel’s endpoint using a large crane.

Micro-tunnel boring, also known as microboring, microtunneling, or micro-drilling, is an advanced construction technique designed for creating small-diameter tunnels or boreholes with high precision. It is commonly used for utility installations, geotechnical studies, and trenchless construction projects.

 

As cities grow more crowded and the need for less invasive infrastructure solutions increases, microboring has become an essential method for reducing surface disruptions while ensuring the efficient installation of underground systems.

What is Micro-tunnel boring?

Micro-tunnel boring is a specialized form of boring that creates tunnels or boreholes with diameters typically ranging from a few inches to several feet. Unlike traditional boring methods, micro-tunnel boring employs remote-controlled drilling machines that operate with extreme precision. The process minimizes the need for large excavation sites, making it ideal for urban environments and sensitive ecosystems.

The technique is used in a variety of industries, including civil engineering, oil and gas, telecommunications, and water management. Depending on the project’s requirements, different types of microboring machines may be employed, such as MTBMs, directional drills, or auger boring systems.

Advantages of Micro-tunnel boring

Micro-tunnel boring provides several advantages over traditional excavation and tunneling methods, especially when it’s important to limit surface disruptions.

Minimal Surface Disruption

One of the most significant advantages of micro-tunnel boring is its ability to install underground infrastructure with minimal impact on the surface. This makes it especially valuable in urban environments, where conventional excavation methods would cause significant disruptions to roads, sidewalks, and buildings.

Precision and Accuracy

Micro-tunnel boring systems are equipped with advanced guidance and control systems that allow for precise placement of underground utilities. This reduces the risk of accidental damage to existing infrastructure, such as gas lines, water pipes, and electrical conduits.

Reduced Environmental Impact

Traditional open-cut trenching methods can cause extensive environmental disruption, including soil displacement, deforestation, and damage to water bodies. Micro-tunnel boring minimizes these impacts by requiring fewer entry and exit points, preserving the surrounding environment.

Cost Efficiency in Certain Applications

While the initial setup cost for micro-tunnel boring can be high, it often proves to be cost-effective in the long run by reducing labor costs, minimizing delays caused by traffic rerouting, and decreasing restoration expenses for roads and landscapes.

Increased Safety

By eliminating the need for deep excavation, micro-tunnel boring enhances worker safety. Trench collapses, falling debris, and exposure to hazardous underground conditions are significantly reduced, making microboring a safer alternative to traditional excavation methods.

Drawbacks of Micro-tunnel boring

Despite its numerous advantages, microboring is not without its challenges. Here are some of the primary drawbacks associated with this technique:

High Initial Cost

Micro-tunnel boring requires specialized equipment and skilled operators, which can lead to higher initial costs compared to traditional trenching methods. Small-scale projects may find it difficult to justify the expense of microboring.

Complex Planning and Setup

Successful micro-tunnel boring operations require detailed planning, including soil analysis, underground utility mapping, and equipment calibration. Any miscalculations or unforeseen subsurface conditions can cause delays and cost overruns.

Limited Diameter Capabilities

While micro-tunnel boring is excellent for small to medium-sized tunnels, it is not suitable for large-scale tunneling projects. For projects requiring tunnels larger than a few meters in diameter, traditional tunnel boring machines (TBMs) or conventional excavation techniques are more appropriate.

Challenging in Unstable Soil Conditions

Micro-tunnel boring can be difficult in unstable or highly variable soil conditions. Loose sands, high groundwater levels, and mixed soil strata can complicate the process and require additional stabilization measures, increasing costs and project timelines.

Applications of Micro-Tunnel Boring in Construction

Micro-tunnel boring is widely used across the construction industry due to its precision and ability to create underground passages with minimal surface disruption. This makes it an ideal solution for various applications.

Utility Installations

Micro-tunnel boring is commonly used to install underground utilities such as water and sewer lines, electrical conduits, fiber optic cables, and gas pipelines. This method allows utilities to be placed beneath roads, railways, and waterways without requiring disruptive open-cut trenches.

Trenchless Sewer and Water Line Rehabilitation

Aging sewer and water lines often need repairs or replacement. Micro-tunnel boring enables the installation of new pipelines within or near existing infrastructure without causing major surface disturbances. This is especially useful in densely populated urban areas where traditional excavation would be impractical.

Geotechnical Investigations

Before major construction projects begin, engineers must assess the ground conditions. Micro-tunnel boring is often used to collect soil and rock samples for geotechnical analysis, providing crucial data for designing foundations, retaining walls, and other structural components.

Drainage and Stormwater Management

Effective stormwater drainage systems are essential for preventing flooding and erosion. Micro-tunnel boring allows for the installation of underground drainage pipes, culverts, and stormwater management systems in areas where open excavation would be too disruptive or costly.

Microtunneling for Transportation Infrastructure

In transportation projects, micro-tunnel boring is used to install underground conduits beneath highways, airports, and railways. This method enables the expansion and maintenance of critical infrastructure without causing major traffic disruptions.

Industrial Applications

Micro-tunnel boring is also valuable in industrial settings for installing pipelines that transport chemicals, oil, and gas. It is particularly useful in environments where surface disruptions could interfere with ongoing operations or pose safety risks.

The Future of Micro-Tunnel Boring

As construction technology advances, micro-tunnel boring is expected to become even more precise, cost-effective, and adaptable to a wider range of conditions. Innovations such as real-time soil monitoring, automated guidance systems, and enhanced drilling materials will further improve its efficiency and accuracy.

With increasing urbanization and the growing need for sustainable infrastructure, micro-tunnel boring will play a key role in shaping modern cities. Its ability to install essential underground utilities with minimal disruption makes it an indispensable tool for future infrastructure development.

How SiteMap® and GPRS Helps Ensure the Safety of Your Micro-Tunnel Boring Projects

Even minimal surface disruption creates a risk of damaging existing subsurface infrastructure. While MTBMs are extremely precise and come equipped with technology designed to help them avoid buried utilities, underground storage tanks (USTs) and other subsurface obstructions, the only way to truly eliminate this risk is to hire a professional utility locating company like GPRS to provide you with complete and accurate data about the built world beneath your project site.

Our specially trained Project Managers utilize the latest subsurface investigation technology, including ground penetrating radar (GPR) scanners; electromagnetic (EM) locators, and CCTV camera-equipped sewer inspection crawlers and push-fed sewer scopes.

We visualize what you can’t see, giving you the data you need to avoid creating costly and potentially dangerous subsurface damage.

All this data is always at your fingertips thanks to SiteMap® (patent pending), GPRS project & facility management application that provides you with accurate existing conditions documentation to protect your assets and people.

Securely accessible 24/7 from any computer, tablet, or smartphone, SiteMap® allows you and your team to plan, design, manage, dig, and ultimately build better by serving as a single source of truth for the data you need to get the job done right.