Municipalities warned after two massive communal hot water tanks collapse
Two underground heat storage tanks recently collapsed in the Netherlands, prompting warnings to about fifteen municipalities with similar installations. The tanks store thousands of liters of heated water to warm homes and buildings.
One of the incidents happened in Nagele, a village in Noordoostpolder, Flevoland. Earlier this year, it became clear that a potentially dangerous situation was developing in a grassy area above one hot water tank, possibly caused by subsistence.
“There was a large crack in the grass. We immediately put up fences so children from the adjacent daycare couldn’t fall in,” said Ruut Schalij, project leader at energy cooperative Energiek Nagele, told Nieuwsuur. The tank was part of a pilot project to store solar-heated water for winter use, but the collapse was too severe to repair.
Independent research by engineering firm Sinko and TNO found the company that installed the tanks used materials unable to withstand prolonged exposure to hot water. Sinko researcher Marcel Keus said, “If you have any knowledge of construction, you know that.” Mayor Roger de Groot warned other municipalities with similar tanks, some of which are located under schoolyards and playgrounds.
In Wernhout, a tank heating a local football club and sports hall also collapsed, creating a pit several square meters wide. Keus noted, “Plastic joints become brittle when exposed too long to water that heats and cools repeatedly. Aluminum pipes were breached, making them vulnerable to corrosion.” The village is home to fewer than 5,000 people, and is part of Zundert, Noord-Brabant.
The installing company, HoCoSto, admitted materials were used incorrectly but blamed overfilling in Nagele for the collapse. CEO Siebe Geerts said the company is inspecting all tanks to ensure other municipalities are safe.
Some municipalities, including Utrecht, Soest, Vlieland, and Veenendaal, have cordoned off their tanks, while most see no need for precautions. Both incidents lacked calculations for the structural capacity of the tanks.
Despite the failures, officials emphasize the importance of pilot projects for the energy transition. Alderman René van Amersfoort said, “It would be a shame if incidents like this stopped us from innovating.” Keus added, “Agreed, but that doesn’t mean we shouldn’t think about basic things, like what materials to use.”
