On May 7, 2023, Kuressaare Hospital reported a mass outbreak of illness within the island of Saaremaa's capital city, with symptoms including diarrhea, vomiting and abdominal pain. The Health Board subsequently confirmed the presence of E. coli bacteria in the drinking water.

A total of 53 people sought emergency medical care due to illness caused by the contamination.

It was determined a few weeks later that the contamination was caused by wastewater entering the water line. The sewer pipe responsible for the contamination ruptured on May 4, and the first case of illness was recorded two days later.

This Monday, Saaremaa municipal government and TalTech released an expert assessment on the causes of the water system contamination.

Saaremaa Municipal Mayor Mikk Tuisk said that the municipality had commissioned the study from TalTech to help prevent similar issues from occurring again in the future.

Incomplete documentation, insufficient oversight

Ivar Annus, a professor of urban water systems at TalTech, emphasized that the aim of this expert assessment was not to assign guilt.

Annus noted that interviews conducted as part of the assessment indicated deficiencies in the water system's construction documentation, and that oversight did not meet contractual requirements. Moreover, there were no documented records of geodetic measurements conducted in the affected area, or of the flushing of the reconstructed pressurized sewer pipe.

According to modeling results, the rupture caused pressure to drop in the water system, both in the immediate area and more broadly across town, making it likely that wastewater entered the system during and immediately following the incident. This low pressure resulted both from the pipe rupture itself and from subsequent emergency operations.

"In the case of such incidents, water sampling should begin immediately," Annus noted. However, in Kuressaare that May, water samples didn't start being taken until after cases of illness had already emerged.

Annus also noted that communication with the public must also be clearer, as residents were confused by the Health Board's communications at the time — particularly regarding whether water deemed unfit for drinking could still be used for other purposes, such as brushing teeth or doing laundry.

Tuisk said that a key lesson for Kuressaare Municipality is that going forward, in times of crises — whether involving water or electricity — the municipality itself will be taking a leading role in the response.

Kuressaare Veevärk exploring permanent chlorination

Martin Haug, a board member at local water utility company Kuressaare Veevärk, stated that water supply incidents are an unavoidable part of water management, but noted that each case is unique, making it difficult to come up with a one-size-fits-all response plan or guarantee that such incidents won't happen again. Even so, he added, risks can be minimized.

According to Haug, the company has improved its internal procedures for handling simultaneous system failures, changes in water flow dynamics or the detection of microbiological contamination.

"If there is any suspicion whatsoever that intersecting communications pose a risk, and if it hasn't been 100 percent confirmed that this risk has been mitigated, we require measurements or excavation to verify the situation," he noted.

Kuressaare's drinking water monitoring plan was also updated last year, increasing the number of control points as well as the frequency of water sampling.

This year, Kuressaare Veevärk will also start looking into the feasibility of a permanent chlorination solution.

"This will certainly require broader public debate on whether such an approach is acceptable or not," Haug added.

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