Hydrogeological drilling
Groundwater studies, observation and monitoring wells, pumping tests.
Hydrogeological wells are drilled to study the level, quality and reserves of groundwater. Unlike an ordinary supply well, their main job is not to deliver water but to measure and observe: how much water the aquifer can yield, how it moves and how it changes over time.
Where they are needed
- Water-supply projects — proving reserves for a village, town or industrial well field.
- Environmental monitoring — tracking groundwater contamination around fuel depots, landfills, plants and oil and gas facilities.
- Construction — designing dewatering for excavations and watching the groundwater level.
- Drainage and land improvement — controlling rising groundwater on farmland and in residential areas.
Types of well
- Test-production wells — drilled for testing and, if the result is good, put into service as supply wells.
- Observation wells (piezometers) — to measure drawdown around a pumped well and for long-term level records.
- Monitoring wells — for regular water sampling, usually upstream and downstream of a site.
- Dewatering wells — to lower the groundwater level temporarily during construction.
How a monitoring well is built
A monitoring well must not change the water it samples, so it is usually built from PVC pipe. The screen is set only against the aquifer being studied, with a gravel pack around it. A bentonite seal above the screen keeps water from other layers and from the surface out. The top is closed with a lockable protective cover.
Pumping tests
Water is pumped from the well at a set rate while the fall in level is timed in that well and in the observation wells, followed by the recovery once the pump stops. From these readings the hydrogeologist calculates the key parameters: the well's specific capacity, the aquifer's transmissivity and the radius of influence. A test can run from a few hours to several days.
At the end of the test, water samples are taken for chemical and bacteriological analysis.
Work sequence
- Agreeing locations, depths and well design from the hydrogeologist's brief.
- Drilling and logging the geological section.
- Installing the screen string, gravel pack and bentonite seal.
- Developing the well until the water runs clear.
- Pumping test and level readings.
- Water sampling and handing over data for the report.
When you get in touch, tell us the purpose of the work, the site, the number and depth of wells and, if you have one, the hydrogeological brief.