Monitoring Well: All Facts You Should Know

Groundwater monitoring wells are primarily used for observing groundwater levels and flow conditions, collecting samples to determine the quality of the groundwater, and assessing the hydraulic characteristics of strata that contain water. Continue reading, you will learn more about monitoring well.

What is Monitoring Well?

Where water meets impermeable material, like a layer of solid rock, aquifers create an underground water reservoir. However, due to the different soil permeability in the area, it lacks the flat, level top that we would expect from surface water, which makes it more difficult to measure the level inside the underground reservoir. It is therefore not unusual to find multiple distinct aquifers at various depths in the same area because they may form at various depths as well. Monitoring wells are drilled and used to check the level of these reservoirs in order to learn more about this water resource.

How Are Monitoring Wells Used?

Monitoring wells, otherwise known as “observation wells,” are primarily used for measuring groundwater levels, flow, and quality. They enable technicians to examine the well’s condition without requiring direct access by taking groundwater samples and performing health assessments.

In order to determine the quality of groundwater, water samples must be taken and sent to a lab where they are examined for any hazardous substances, biological samples, tracer studies, and measurements of water levels. The aquifer—a rock that stores and transmits groundwater to the well—and the populations of groundwater species that live there can both be evaluated with the aid of monitoring wells.

The aquifer can be kept free from contaminants like runoff and pests by performing proper installation, routine maintenance, and using top-notch monitoring well equipment. Municipalities and homeowners can save money by reducing the number of resources required for good maintenance by using cameras and other high-tech equipment.

What is Groundwater Quality Sampling?

Monitoring wells enable evaluation of the chemical, biological, physical, and/or other characteristics of groundwater within an aquifer, as well as the direction of groundwater flow. Wells are frequently sampled on a regular basis (e.g. monthly, quarterly, annually), as directed by local, state, or federal regulatory agencies, to understand trends over time and to make decisions about necessary remedial actions.

What Are Groundwater Monitoring Well Installation Basics?

At locations where various contaminants, such as petroleum compounds or chlorinated solvents, are known to be present or are suspected to be present, groundwater monitoring wells are frequently installed.

What is Monitoring Well Design?

Depending on their intended use, the diameter of a monitoring well may vary. These wells are typically made of stainless steel or polyvinyl chloride (PVC). The materials used to build monitoring wells and the kind of equipment used to install them are determined by site-specific elements like the project goals and the local geologic conditions.

How Are Monitoring Wells Installed?

Monitoring wells are installed into the underlying aquifer by various types of drilling methods, including:

• Hollow Stem Auger
• Solid Stem Auger
• Direct Push
• Air Rotary
• Mud Rotary
• Water Rotary
• Sonic

What Are the Monitoring Well Issues?

If a monitoring well is not constructed or installed correctly, it may produce groundwater samples that are not only of poor quality but also do not accurately reflect the groundwater conditions under a Site. Therefore, information gathered from a well that was improperly developed or installed may result in incorrect conclusions about the environmental quality of the Site and, ultimately, the implementation of improper corrective actions that could present financial and/or health and safety risks to property owners, operators, and the general public.

How Are Monitoring Wells Developed?

In order to confirm that the good materials are in place, monitoring well development typically occurs at least 24 hours after installation is complete and involves extracting large amounts of water from the well while evaluating specific water quality parameters. Various techniques, such as bailing, pumping, surging, backwashing, jetting, and/or airlift pumping and surging with compressed air, can be used to monitor the progress of a well.

In accordance with the U.S. Environmental Protection Agency (EPA), well development activities must continue until the water inside the well is clear of sediment and the pH, temperature, turbidity, and specific conductivity stabilize. Development might need to go on for several days if there is a lot of sediment still in the water. Sampling can start after the well has been constructed and the parameters of the groundwater have stabilized over the necessary period of time.

How Are Monitoring Wells Installed?

Since there is no one-size-fits-all approach to installing wells, it is crucial to choose the best drilling technique based on the goals of the project and the physical environment where the well will be located. Inadequate installation or maintenance could pose a serious threat to groundwater quality because these kinds of wells are purposefully placed in regions that may be affected by high levels of pollutants.

The following are some of the drilling methods used for monitoring well installation:

Hollow-Stem Augering

Attaching the spiral-shaped drill bit to a hollow stem as opposed to a solid one is known as “hollow-stem augering.” The hollow stem acts as a temporary casing to stop the borehole’s sides from collapsing. This technique enables quick, simple, and affordable drilling into clay and soft soils.

You can get continuous cores by locking a thin-walled tube into the lowest auger and inserting it there. The tube needs to be retracted using a wireline to hoist it up once the hole’s depth exceeds the auger’s length.

Cable Tool Drilling

When using a cable tool, the drill bit that will be lifted and dropped alternately has a claw bit attached to a weighted drilling string. The ground material becomes looser after being lifted and dropped repeatedly and combines with water to form a slurry. Then, a bailer is used to periodically remove the slurry and tiny rock fragments from the hole.

As drilling progresses, steel casing should be driven into the ground to reinforce the borehole wall in softer soils to prevent collapse. A well can then be built inside the steel casing after this is finished.

Rotary Drilling

To obtain rock samples or to drill deep observation holes, rotary drilling is a technique. This technique involves driving a rotating drill bit, also known as a rotary, into the ground until a hole with a large diameter is created. Typically, casings are used during drilling to keep the well hole from collapsing.

Two rotary drilling methods used in monitoring well installation include:

• Mud Rotary Method

The drill bit is connected to hollow drilling rods in the mud rotary method. The drill bit then starts to rotate quickly in order to drill through the borehole. Drilling fluid is pumped through the rods and up between the rods and the borehole to remove drill cuttings. In order to cool the fluid and keep the borehole from collapsing, it then flows into a mud pit and is pumped back through the rods. In order to ensure that all of the drilling fluid is removed after construction, it might be necessary to engage in extensive remediation.

• Air Rotary Method

The air rotary method involves forcing air down drill rods using an air compressor. Air is used as the drilling fluid. Then, between the drill string and the hole wall, the air escapes through the drill bit and returns to the surface. The ascending air pulls cuttings out of the ground and collects them near the drilling rig. To prevent contaminated materials from entering the borehole, the air in the area should be filtered both during and after drilling.

How Do Monitoring Wells Differ from Water Wells?

It’s a common misconception that water wells and monitoring wells are the same things. However, monitoring wells enable technicians to gather groundwater samples, measure water flow, and evaluate the well’s condition without the need for direct access. As an alternative, water wells draw water for domestic, industrial, or commercial use from the ground using pipes and pumps.

Conclusion

It might not appear to be an easy task to install a monitoring well. But with the right equipment and knowledge, it can be accomplished quickly by a group of knowledgeable experts.