On May 7, 2023, Kuressaare Hospital reported a widespread outbreak in the city of illnesses characterized by diarrhea, vomiting and abdominal pain. Following this, the Health Board detected the presence of E. coli bacteria in the drinking water.

It was determined a few weeks later that the contamination was caused by wastewater entering the drinking water system. The sewer pipe that served as the source of the pollution had ruptured on May 4, while the first reported case of illness occurred on May 6.

On Monday, the Saaremaa municipal government and Tallinn University of Technology (TalTech) published an expert assessment of the causes of the water network contamination. Municipality Mayor Mikk Tuisk stated that the municipality had commissioned the study to prevent similar incidents in the future.

Monitoring not in line with contract

Professor of urban water systems Ivar Annus stressed the expert assessment was not conducted to determine culpability.

He noted that interviews conducted for the assessment suggested deficiencies in the construction documentation of the water network and that supervision did not comply with contractual agreements. Additionally, there was no documented evidence of geodetic measurements carried out in the accident area or of the flushing of the reconstructed pressurized sewer pipe.

According to modeling results, the accident caused negative pressure in the water network both in the affected area and across the city. This made it likely that wastewater entered the system during and immediately after the incident. The negative pressure was caused both by the pipe rupture and by the emergency response measures that followed.

"In cases of such accidents, water sampling should begin immediately," the TalTech professor said. However, in the Kuressaare case, water samples were taken only after illness cases had already appeared.

Annus also stated that the messaging to residents should be clearer. Many locals found the Health Board's communication confusing, particularly regarding whether the water that was deemed unsafe for drinking could still be used for brushing teeth or washing clothes.

Mayor Mikk Tuisk said the key lesson for Kuressaare Municipality is that in crises — whether related to water, electricity, or other issues — the municipality will take the lead in crisis management going forward.

Permanent chlorination solution sought

Martin Haug, a board member of Kuressaare Veevärk, stated that accidents are an inherent part of water management. Each incident is unique, making it difficult to develop a universal approach or guarantee that such events will not recur. However, risks can be minimized.

Haug said the company has updated its internal procedures regarding how to respond when there is a simultaneous failure in the network, a change in water flow dynamics or a microbiological finding.

"If there is any suspicion that intersecting utility lines pose a risk, and if it is not 100 percent confirmed that the danger has been mitigated, we will require measurements or excavations to verify the situation," he explained.

Additionally, in 2024, Kuressaare's drinking water monitoring plan was updated, increasing the number of control points and the frequency of sample collection.

This year, Kuressaare Veevärk will also begin researching a more suitable permanent chlorination solution. "This will certainly require broader public discussion on whether it is a desirable or undesirable measure," Haug said.

--

Follow ERR News on Facebook and Twitter and never miss an update!