Piezometer standpipes are tubes with a perforated part, which is placed in the ground in order to determine the groundwater level (i.e. the phreatic water table) or to monitor the quality and quantity of the groundwater. You can find the best piezometers for measuring groundwater levels at Gouda Geo-Equipment.
How our piezometer standpipes determine groundwater levels
The perforated part of the piezometer standpipes is called the filter tube and is in general 1 or 2 meters long. The “blind” or imperforated part of the piezometer standpipes is called the riser tube. The diameter of the standpipe is large enough to ignore for the capillary to rise inside the tube. This implies that the water level inside the piezometer standpipes indicate the position of the phreatic water table when the groundwater has had sufficient opportunity to enter the tube and stabilize. The time it takes to stabilize and to consider the data as correct, depends on the purpose of the measurements and soil type.
By placing a perforated tube in the ground, you can take either groundwater samples, determine the groundwater level, sample and to measure the thickness of floating and sink layers, and / or to determine the permeability of the ground (at the height of the filter).
The piezometer standpipes can be placed in the ground in different manners dependent on the purpose of the measurements and groundwater tests. The position and the length of the filter tube may vary. In principle two different filter positions are possible, i.e.:
- The filter tube intersecting the groundwater level
- The filter tube below the groundwater level
When the filter tube is placed as such, that it intersects the groundwater level, it will be made possible to locate a floating layer containing hydrocarbon particles.
A nylon filter stocking placed around the filter tube combined with coarse sand or gravel deposited around the filter tube, prevents that soil particles pour through the slot perforations and cause clogging of these slots. A bentonite plug positioned at the right depth(s) above and possibly below the filter tube guarantees that only groundwater from the targeted soil layer is extracted.
The piezometer standpipes for measuring groundwater levels are traditionally placed using CPT drilling techniques. It is much more efficient and economical to place these standpipes using the direct push capabilities of a CPT penetrometer pushing rig. This can be done using 55 mm casing tubes and a so-called lost tip. These casing tubes and tip are pushed to the desired depth. Subsequently the piezometer standpipe, composing of a filter and riser tubes, stocking and bottom plug, is lowered into the string of casing tubes. The string of casing tubes is pulled up the same moment the void between the string of casing tubes and piezometer standpipe is filled out with coarse sand. As soon as the string of casing tubes is fully retracted, the hole can be finished off with soil and a protective cylindrical case or street-covering hood can be placed to protect the standpipe.
In general, the exact position of the piezometer standpipe is determined using a theodolite and this position is logged in a (triangular) coordinates grid in order to store the measured data in a Geographic Information System (GIS). Multiple piezometer standpipes can be part of such a measuring grid.
Groundwater level measurements can either be done manually using one of the groundwater level meters or automatically by means of submersible piezometer dataloggers (Divers). The latter enable more frequent measurements, e.g. every single hour or several times per day. The Gouda-Geo piezometer standpipes for measuring groundwater levels are made of high-density polyethylene (HDPE) and are in accordance with Kiwa K561 class A regulations. The slots are 0.3 mm wide. The full product range comprises the following:
Use our equipment to gather data about the soil or groundwater levels
Aside of piezometer standpipes, you can also use our pore pressure meters to gain more data about the characteristics of the groundwater at your investigation site. Contact us to learn more about these products and choose those that suit your projects best. You can either call (0)715 318 475 or send an email to firstname.lastname@example.org. Gouda Geo-Equipment is your Dutch CPT manufacturer with years of experience. We develop professional geotechnical equipment for over companies in over 131 countries and you can reach us 24/7.