Q&A on the Schellingwoude Water Main Break
Situation
What happened?
Around 2:00 a.m. on the night of August 30, a large wastewater pressure pipeline operated by Waternet ruptured near Schellingwoude. As a result of the rupture, a large volume of sewage flowed into the surface water system. This led to a sharp drop in the oxygen level in the water, causing, among other things, fish mortality.
What is the contaminated area?
- Amsterdam North
- Zunderdorp
- Ransdorp
- Monnickendam / Waterland
The contaminated area includes parts of Amsterdam-Noord and the surrounding rural areas where the effects of the pressure pipe rupture are noticeable. Due to precipitation and the flow of the water system, the contaminated and diluted water has spread through Zunderdorp, Ransdorp, and toward Monnickendam, among other places.
This has also affected the municipality of Waterland. The area around Monnickendam is part of the region where measures are being taken and where water quality is being monitored.
Because the situation is evolving and water quality varies by location, the area is continuously monitored.
How is the situation now compared to the first few days after the breakup?
The situation has changed. Several measures have now been taken to improve water quality, including the installation of aeration pumps and the deployment of additional pumps to supply cleaner water. Recent measurements show that water quality is improving in parts of the affected area, although it remains inadequate at some locations.
Why was the initial estimate two to three days, when recovery is now taking longer?
The earlier estimate of two to three days referred to the expected time it would take to flush the contaminated water out of parts of the water system. That was not a forecast for the repair of the damaged pipe itself. It later turned out, moreover, that the extent of the contamination was greater than initially assumed and that the affected area was larger.
Why has water quality improved in some places but not yet in others?
The water system consists of many small ditches and waterways. As a result, the contaminated water does not spread and dilute in the same way everywhere. Flow rates, oxygen levels, and weather conditions also vary by location.
When did you start removing the dead fish?
HHNK and Waternet jointly began removing the dead fish on Wednesday, September 2. In the days leading up to that, the extent of the pollution was not yet fully clear. Based on reports of dead fish and the measurements taken, it became clear on Monday, August 31, and Tuesday, September 1, that the situation was more serious and widespread than initially assumed.
How many kilograms of dead fish have been collected so far?
We do not measure this. Removing the dead fish is part of the joint effort to restore the area as quickly as possible.
Why weren't the fish culled until later?
In hindsight, the cleanup of the dead fish could have been started sooner. In our initial assessment, we assumed that the sewage had been significantly diluted by the heavy rainfall over the weekend and that the impact on surface water would therefore be limited. In the days that followed, it became clear that the extent of the pollution was greater than initially thought. It also became clear that the affected area was larger.
In addition, the water system in this area is complex. As a result, the contaminated water could not simply be pumped out at a single location. Initial indications and reports—including reports of dead fish—made it clear that additional measures were needed.
Are fish still dying?
No, we haven't received any more reports of dead fish or fish in distress. The oxygen levels in the water are also recovering well.
Noticeable effects in the area
Why do I see grey water or brownish-black flakes in the water?
Due to the discharge of sewage, the water grey may be discolored or dark in color, and brown or black flakes may be visible. These may include diluted sewage and fecal matter. They may also be small pieces of peat that float to the surface due to gas formation. We are observing that the discoloration is now rapidly receding from the area.
Why does the water smell different than usual?
The discharge of sewage has introduced additional nutrients into the water. This triggers various natural processes in the water. Among other things, these processes can produce a gas that smells like rotten eggs. As a result, this odor may be noticeable in the area for a short time.
Where is the contaminated water discharged?
This is discharged either via the Kadoelen pumping station into the North Sea Canal or via the De Poel pumping station into Lake Markermeer.
Why have some locks been hit harder than others?
Local variations may arise due to differences in water flow, water depth, oxygen levels, and the paths along which the contaminated water has spread.
Using the Water
Recreation
Can I swim or go boating in the affected area?
Due to a break in the pressure pipe, sewage has entered the surface water. Therefore, the recommendation is not to use the surface water in the affected area.
Can I swim in places where the contaminated water has been discharged, such as the Markermeer?
It is always a good idea to check the current swimming advisory for a particular swimming location. The province is responsible for ensuring the safety of swimming waters and, based on the water quality data it receives, may issue a negative swimming advisory or a swimming ban for official open-water swimming locations. For more information, visit www.zwemwater.nl
What are the risks of coming into contact with the water?
To do so, please contact the GGD.
What should I do if I've come into contact with the water?
In that case, follow standard hygiene practices: rinse with tap water and soap, and keep an eye on it. If you develop any symptoms, contact your family doctor or the GGD.
How long is the recommendation in effect?
The advisory will remain in effect until measurements show that water quality has sufficiently recovered. A further announcement regarding this will be made on www.hhnk.nl/persleidingbreuk
Animals
Can my pet drink from or swim in the water?
If your pet is showing any symptoms, consult your veterinarian. Before swimming, it’s a good idea to check the advice that applies to a particular swimming location. The province is responsible for ensuring the safety of swimming waters and, based on the water quality data it receives, may issue a negative swimming advisory or a swimming ban for official open-water swimming locations.
Agriculture
Can I use water from the ditch for watering?
As long as this advisory remains in effect, it is not recommended to use surface water from the affected area.
I watered my vegetables with the contaminated water. Can I still eat them?
To do so, please contact the GGD.
What alternatives are there to irrigation?
Rainwater is the very best, so we always recommend it.
Measures and Recovery
What measures have been taken since the pipe burst?
A detour route for wastewater discharge was immediately set up. In addition, aeration pumps have been installed, additional pumps are being used to supply cleaner water, dead fish are being removed, and surface water is being monitored at various locations.
What are you doing to prevent further fish deaths?
To increase the oxygen content in the water, aeration pumps have been installed at several strategic locations. In addition, extra pumps are being used to bring in cleaner water and further dilute the contaminated water.
Has the pressure line been repaired yet?
No. Waternet is working on the repair. It is expected to take at least two weeks.
Why does recovery take at least two weeks?
Repairing a pressure pipeline of this size is technically complex. Waternet is working day and night on the repairs. At the same time, wastewater discharge must continue to be ensured via a temporary diversion route. For this reason, the repairs are expected to take at least two weeks.
Is there still a danger to the surrounding area from the pipe break itself?
At this time, there is no danger to the surrounding area from the pressure pipe.
What will happen if there's a lot of rain again?
Various scenarios have been developed to address changes in weather conditions. The organizations involved are closely monitoring the situation and will take additional measures as necessary.
What tests do you perform?
Water samples from the ditches are collected and analyzed several times a day at various locations. Among other things, the water quality and its changes are monitored.
How often are measurements taken?
Samples of the ditch water are taken several times a day at various locations.
When will the test results be available?
We expect the results of the water samples approximately 15 business days after sampling. Our specialists will then evaluate the results. Only then can we draw reliable conclusions about water quality.
How long will you continue to take measurements?
The parties involved will continue to monitor water quality as long as there is cause to do so and until there is sufficient understanding of the recovery of water quality.
Which organizations are involved in the measurements?
Sampling is performed by an accredited laboratory with expertise in aquatic sediments and surface water.
Communication
How can I stay up to date on new developments?
We are sharing the latest updates regarding the water main break on our website www.hhnk.nl/persleidingbreuk
Where can I go with questions?
Through the contact form you can submit your questions. We are available by phone on weekdays from 8:00 a.m. to 5:00 p.m. at our general phone number, 072 - 582 8 282.
Can I report dead fish?
Yes. If you see dead fish or fish gasping for air at the water's surface, please call us during business hours (8:00 a.m.–5:00 p.m.) at 072-582-8-282, and outside business hours at 0800-1430.