Page 26 - Energize August 2022

NEWS

One small sensor helps: Toutvenant
The mix of sand and gravel that is
The Grensmaas project excavated is called ‘toutvenant’. In the
south of Limburg, it consists of 80% gravel
and 20% sand. It is excavated with huge
excavating machines and transported
with specially designed trucks. “More to
n the Dutch province of Limburg, the Grensmaas Consortium extracts about one hundred the north of the province, the toutvenant
thousand tonnes of gravel every week, a quantity that requires an enormous logistical consists more of sand than gravel. That has
Ioperation. Stopping the process is not an option, and certainly not unannounced. With to do with sediments from the time of the
one single sensor, Hans van der Meer can monitor that risk. ice age.” The gravel is rinsed and sorted
Hans van der Meer, head of production and technical services at Grensmaas gravel using an ingenious system of conveyor
extraction site says, “To give you an idea, one ton equals eleven wheelbarrows. On an belts, sieving machines, washers, screw
annual basis, we extract four and a half million tonnes of gravel at this site. And this gravel conveyors and so on. Each dimension of
extraction is an important part of the Grensmaas project. It is the financial engine and gravel has its own final destination, from
therefore one of the three important pillars of the project. Thanks to this gravel extraction, asphalt to decorative gravel.
there are no costs for the taxpayer, and we create high water protection and nature During our visit, the Grensmaas shows
development. We call it self-realisation,” Van der Meer explains. its capricious nature. “Look”, says Hans,
“the river is much wider now than a few
Gravel extraction weeks ago. Because of the rain, the river
Back to the gravel extraction - what better example of a win-win-win situation could be now takes up much more space and
found in this country? In 1993 and 1995, the province of Limburg was confronted with two mountains of gravel, which were lying
floods on the river Meuse, which caused €200 million in damage. Society demanded more on the bank a fortnight ago, are now in
flood safety, but the cost of some €700 million was a stumbling block for years, until an the water. There is also a huge difference
agreement was made with Consortium Grensmaas - a partnership of contractors, gravel between summer and winter. In summer,
producers - and ‘Natuurmonumenten’ - the Dutch organisation for the conservation and the average flow is about 40 m3 of water
development of nature. Both high-water safety and nature development would be paid per second; in winter, it can be as much as
for with the proceeds from sand and gravel extraction along the Meuse. In the meantime, 2500 m3. During the floods of 1993 and
the river has been given 350 ha extra space to drain off water. That is the size of some 500 1995, it was around 3200 m3.”
football fields. The stream bed was widened, banks lowered, and dikes raised.
The residents noticed it immediately: after long periods of rain the water level rises less Water level
quickly and stays lower. The land in the south of Limburg now stays dry at the same water Due to the nature of the production
level as in 1993 and 1995. And along the Maas, 1000 ha of new natural features are being process, progress is largely dependent
created, which in time will attract a million cyclists and walkers, as studies have shown. on the water level in the Meuse. This
Back to gravel extraction for the Grensmaas project, with which the Consortium must water level fluctuates greatly, which is
recoup its investment of €700 million for flood protection and nature development. That also affected by the operation of the
depends on the smooth running of the logistical process. “All the minerals are transported locks. Van der Meer wanted to be able
by barge, and the ships have to be able to come and go continuously. It is a constant puzzle to monitor and record the water level
to be able to transport everything at the right time,” Van der Meer underlines. properly, also for the communication with
Rijkswaterstaat. “In the harbour, I have
mounted a level sensor on a mooring
post that communicates the water levels
with the cloud via a LoRa network. This
system from Keller gives me up-to-date
information about the water level on
a dashboard in my office. The firm’s
Martijn Smit helped us get the system up
and running and thanks to the sensor’s
communication with the company’s
own Kolibri cloud, we now have all the
information we can from that sensor.”
If the water level is too low or too
high, the process may come to a halt. “We
had a feeling the water level fluctuated
much more than the Directorate-General

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