The field of hydrogeology is made up of two components: hydrology, the study of the movement, distribution, and management of water on Earth; and geology, the study of Earth’s physical structure, its history, and the processes that act on it.

Hydrogeology, also known as geohydrology or groundwater hydrology, is essentially the study of groundwater. It is particularly concerned with how water enters the ground, how it flows underground, and how it interacts with surrounding soil, rock, and other objects.

It is essential to know the characteristics of groundwater near the drill site and understand how it can affect drilling operations. Therefore, for some trenchless construction projects, it may be necessary for engineers and contractors to work closely with professional hydrogeologists.

What Do Hydrogeologists Do?

Hydrogeologists are involved in several different project areas, including sustainable water supplies, food and energy production, environmental protection, and climate change management. They usually collaborate with professionals from various industries and disciplines, including engineers and scientists, sociologists, planners, and economists.

Some of the most common duties of hydrogeologists include:

  • Assisting in the design and construction of water wells for potable water supplies or irrigation.
  • Developing plans to ensure the availability and sustainability of water supplies.
  • Assessing the quality of underground water supplies and their suitability for various uses.
  • Analyzing groundwater pollution and developing schemes to clean or minimize this pollution.

In the trenchless construction industry, hydrogeologists typically work with engineers and contractors to ensure the safety and performance of subterranean drilling operations and underground construction.

Hydrogeologists will usually provide analysis reports along with recommendations on how to minimize the adverse impact of groundwater on drilling while protecting natural groundwater sources from construction activities.

The Role of Hydrogeology in Trenchless Drilling and Construction

Hydrogeology is the branch of earth science concerned with the flow of groundwater in soil, rock, and other porous subterranean media. The flow of fluids in underground formations is especially a concern for drilling projects in the water/wastewater and oil and gas industry.

Hydrogeologists, tunnelers, and geotechnical experts typically work together on relatively large trenchless construction projects, combining their experience and expertise to manage challenging groundwater conditions that are encountered (or may be encountered) on site.

This collaboration ensures that projects are completed safely, on time, and with minimum impact on the environment.

During construction, hydrogeologists may be responsible for the following elements to trenchless projects.

Preserving Aquifers

One of the main tasks of a hydrogeologist is assessing the behavior and characteristics of underground aquifer systems. They do this mainly through simulation of the hydrologic system using computer models and scientific formulas. Accurate simulation requires a vast knowledge of aquifer systems, their properties, and the existing boundary conditions.

The presence of aquifer systems, or any other water-bearing formations, near the work zone is a concern for drillers. Contractors are, therefore, required to work closely with hydrogeologists to take the necessary precautions to protect freshwater aquifers from contamination during construction activities.

Water in aquifers can also flow into trenchless tunnels and contaminate drilling fluids, causing stability or control problems. (Read Mixing the Mud: The Science of Drilling Fluid in HDD.)

When hydrogeologists are engaged in the early stages of construction planning, the issues associated with water inflows can be significantly minimized. (Read Inflow and Infiltration Effects on Sewage Systems.)

Water Well Design and Construction

Hydrogeologists are also actively involved in the drilling of water wells. These structures, which are responsible for bringing groundwater to the surface, are constructed mainly by digging or drilling, followed by pumping.

Water from wells is primarily used as potable water sources; therefore, proper well design and construction is essential to maintain the health and safety of the people who will use it. Some of the factors which hydrogeologists need to consider during well design and construction include:

  • Well construction methodologies.
  • Drilling methods.
  • Aquifer stability.
  • Well testing.
  • The quality of the groundwater.
  • The expected yield of the well.

Contamination Control

Groundwater contamination occurs when fluids seep into natural groundwater sources, such as aquifers, and mix with existing groundwater. Gasoline, drilling fluids, and heavy metals are some of the most common types of contaminants that can be produced as a result of drilling and construction operations.

Underground structures, such as pipelines and storage tanks, may also contain chemicals that can enter the surrounding soil via leaks and make their way to groundwater sources.

Another, albeit debated, source of groundwater contamination is hydraulic fracturing (fracking). The chemicals used in hydraulic fracturing can seep into fissures and cracks and combine with water in aquifers. In 2016, the Environmental Protection Agency (EPA) released a report which confirmed that groundwater could be affected by fracking.

As a result, hydrogeologists should be involved as early as possible during pipe/tank construction and hydraulic fracturing operations to assist in developing contamination or pollution control plans prior to construction.

Trenchless Construction Management and Sustainability

The success of trenchless construction operations depends largely on the proximity of the drilling location to nearby groundwater sources. Unmanaged groundwater levels can jeopardize horizontal directional drilling (HDD) operations, for example, by affecting borehole stability or contaminating drilling fluid.

Hydrogeological reports are, therefore, required to provide essential information on groundwater fluctuations as well as dewatering requirements.

Additionally, the chemicals used in drilling fluids, particularly oil-based muds (OBM), have come under heavy scrutiny due to the presence of toxic chemicals and additives. In this case, hydrogeologists will assess nearby groundwater sources and analyze their susceptibility to contamination from drilling fluids.

What We've Learned

The success of drilling and construction operations depend heavily on the subterranean conditions at the proposed site. Aquifer locations and groundwater movements are just some of the elements that need to be properly investigated to ensure that neither the drill site nor the surrounding waterways are compromised during construction.

As such, hydrogeological professionals must be consulted as early as possible when formulating drilling plans and construction methodologies.