Groundwater Level Monitoring with standpipes and piezometers
Groundwater level monitoring measures the water level in the ground, and the pore water pressure in specific layers, at installed standpipes and piezometers. It establishes the design groundwater level, checks the performance of dewatering, tracks pore pressure build-up and dissipation during compaction, preloading and consolidation, and watches for effects on neighbouring structures. Readings are taken manually with a dip meter or automatically with data loggers.
When the test is used
Typically used for…
- Dewatering systems and excavations below the water table.
- Consolidation with preloading and vertical drains.
- Dynamic compaction and vibro works in saturated soils.
- Seasonal and tidal groundwater variation for design.
Limitations
- A standpipe shows the combined water level over its response zone; a sealed piezometer is needed for a single layer.
- Instruments must be protected from damage on an active site.
- Readings need a consistent datum and frequency to be useful.
The test type, number and locations are agreed with the consultant for each project.
How the test works
A borehole is drilled to the target layer and a standpipe with a slotted section, or a piezometer sealed within the layer, is installed with a filter and bentonite seals. The top is protected by a cover and surveyed.
Water levels are read with a dip meter, or pressures are logged automatically by vibrating wire or pressure transducers, at the agreed frequency, and plotted against time and the works.
Test planning inputs
- Purpose: design level, dewatering performance or pore pressure response.
- Instrument type, locations and response zones.
- Reading frequency and trigger levels where used.
- Datum and survey reference.
- Reporting requirements.
Calibration and equipment checks
- Instrument installation records and response tests.
- Baseline readings before the works start.
- Logger and transducer calibration checks.
Test execution controls
- Installation depth, filter and seals recorded.
- Readings taken to a consistent datum and frequency.
- Instruments protected and checked after damage.
- Logger data downloaded and checked.
Interpretation and reporting
The test plan, the raw record and the interpretation are kept separate, so it is always clear what was specified, what was measured and what it shows.
What is specified
Monitoring purpose, locations and any trigger levels agreed with the consultant.
What was measured
Installation logs and readings for each instrument.
What it shows
Time plots and interpretation, in the monitoring report.
Deliverables
- Monitoring plan
- Installation records
- Reading records and logger data
- Time plots
- Monitoring reports
Discuss the testing your project needs.
Share the project stage, the ground conditions and the specification or acceptance criteria.