Control and maintenance
The maintenance of the drain starts with the regular check of the drain and if necessary, cleaning and repair of the end pipe. Whether major maintenance is required depends on the result of the check. In this chapter, we will treat the topics of control and Maintenance
Drainage end pipe
Periods with lots of rain can be used to check if all end pipes drain well enough. You can collect water from some pipes and the quantity that has been removed can be measured. This can be converted into millimeters per hectare. To do this, you have to track the number of seconds it takes to collect 1 liter. And with this information, you can use the following formula:
- L = Lengtt of the drain pipes (meters)
- A = Length between two drainage pipes (meters)
- T = the time measured(seconden)
- M = amount of drainage in 24 hours (millimeters)
The outcome of this formula must be at least 7 millimeters. If the results show that too little water is being discharged, the power tube must be checked first. It is possible that during application this has been applied in ascending order. By pushing down on to the tube, it may completely disrupt the drain or cause the end tube to separate from the drain. If the end pipe is correct, the cause must be sought in the drain.
To investigate the probable cause of a poorly running drain, several drill holes can be made. In these drill holes, water must not flow over the surface of these boreholes. Even more accurate is the installation of several vertical groundwater level pipes, with a length of approximately 1.20 meters. If this is perforated over its deepest length over which a sleeve has been pulled, an excellent filter is obtained. The water level can be read regularly in this tube. By placing them right next to the drains and between the drain, the influence of the drain can be measured. By placing one or more at several distances from the power tube, an impression of the hydraulic gradient is also obtained and the presence of airlocks or a negative gradient can also be demonstrated. The water level can be checked approximately 24 hours after the monitoring wells have been placed or drill holes have been made. With good drainage, the results should be as shown in figure 1 A. In this case the groundwater level may be above the drain, but no more than 10 to 15 cm. If the results are as indicated in figure 2 B, then either;
- the ditch level is temporarily too high, which results in drains being underwater
- the drainpipe is too small in relation to the surface
- the tube is clogged, soiled, or disturbed
If the pipe dischargers to little or no water, the casing material or perforations in the drain may be blocked (figure 1C). This can be seen through puddles forming on the plot while the groundwater level is low and the drains do not or hardly drain. In this case, the drainage works well, but the cause is compacted or congested soil. This can occur on a plot that has been cultivated under unfavorable conditions. Grassland is sensitive to this, for example, when it has just been sown. The cutting (clay) or compacting (sand) can then easily occur during an intensive rain shower. Even after heavy leveling, there is a risk of disturbance in the profile. Even after heavy leveling, there is a risk of disturbance in the profile. In these cases, the solution must be found in a profile operation. A poorly permeable layer can easily occur deeper in the profile. This can be caused naturally, but it can also occur after processing. This can be solved through profiling. There is various equipment for this. The entire profile can also be poorly permeable. This cannot always be improved through profiling. Figure 2 F, shows excellent draining, but the drain distance is too great. In this case, interim drainage will often be necessary. When checking the drain trench, one more borehole must be made, or one monitoring well must be placed in the drain trench. One hole or monitoring well approximately one meter from the drain and one hole or monitoring well must be placed in the middle between the drains. In figure 2 F it can be established that the drain trench is poorly permeable. The cause may be that the side of the drain trench is smeared while digging the trench.
Remaining control methods
In addition to monitoring the construction of drainage and the operation via monitoring wells and measuring the discharge, there are other monitoring methods. Such as the method in which a transmitter is placed in the drain using a hose. The transmitter emits radio waves which are received above-ground. This way, a possible malfunction can be accurately traced to less than half a meter. This can prevent unnecessary digging. The pierce ability can be checked with a piercing device. The back pressure which the head of the piercing device experiences in the drain is thereby measured. If the resistance is too high, the pipe may be dirty or there may also be obstacles in the drain. Sometimes deformation of the pipe has already occurred during construction. The drain can also be compressed if the location of the drain is too shallow or damaged during deep tillage. Another device is the drain scope. A recording device and a light source are placed in the drain through a puncture in the drain. This way you can look into the drain and, if desired, record the degree of pollution or malfunction on a photo.
End pipes have to manage large amounts of water. And are also easily disturbed or damaged. By regularly checking them and then systematically inspecting them in spring and autumn, disturbance in the drainage system can be limited. The disturbance can occur due to vegetation, grazing livestock, but also due to the mechanical cleaning of ditches. Pipes damaged by frost or ice must also be repaired as quickly as possible. When draining iron-rich water, the power pipes must be cleaned a few times a year. This takes relatively little time. Often the first few meters of the pipes contain a lot of rust. This can easily be removed with a hose of only a few meters.
Especially in the periods after the construction of the drainage, contamination with soil particles can occur. Since the soil around the drain has not yet stabilized. This is most common with fine-sand lutum poor soil. The parts are easily moved with incoming water in and around the drain and can deposit in the drain and the perforations. The wrapping material can also become clogged this way. The change of this increases if the groundwater is higher during the construction of the drainage. There is also a risk of soil being washed in if the encapsulation material is too coarse or if it is completely lacking. On calcareous soils, an organic coating such as coco’s or coco’s peat may be completely digested. Iron can also disrupt the drainage of water. This can be temporary, but also permanent if there is a water supply from seepage.
If through observation it appears that the drains have insufficient water discharge concerning the measured groundwater level, some randomly selected drains can be flushed through. If there are no complaints about the drainage condition of the plot after drainage and the drains are being used regularly, then there isn’t a reason to flush the drains. This is because unnecessary flushing can also set soil parts in motion in such a way that they settle in the drain immediately after flushing. As a result, the contamination after flushing is even greater before ‘cleaning’. If contamination is still observed regularly, maintenance once every 5 to 10 years is useful. If you have iron it is sometimes necessary to flush every year or even several times a year. It is not useful to clean through automatic data. It is recommended to always start with a random check before monitoring.
The time of flushing is important given the risk of discharge of the loosened material. This chance is greatest when the pipe itself drains water. The amount of water entered is usually only for loosening the dirt in the drain. The excess groundwater that is discharged through the drain is also responsible for the removal of the dirt from the drain. Cleaning of drains in the summer, when the groundwater level is low, is therefore not recommended. The most favorable time is between November and the beginning of March. During this period a lot of water is being drained because the precipitation exceeds the evaporation. When cleaning is done in autumn, you will notice the advantage of a better functioning drain in spring.