Tests fail to identify source of Saue water contamination

Tests have failed to identify the source of E. coli contamination found in private wells in the northwestern part of Saue town in mid-August, ERR reported. No contamination was detected in the public water supply.

After the bacteria were discovered, Saue municipality took water and soil samples, inspected wastewater systems and pipelines, and involved the Environmental Board, Health Board, Rescue Board, AS Tallinna Vesi and the Estonian Geological Survey.

Estonian Geological Survey hydrogeologist Andres Marandi said the available information suggested that several factors may have contributed to the contamination. Microbiological contamination may already have been present in the soil and shallow groundwater, while low summer water levels, the condition of private wells and excavation work on Rauna Street may have affected the movement of water through the soil.

The municipality received its first report of a possible water-quality problem on August 17. Three more reports followed the next day, after which the municipality informed residents about contamination in private wells. A crisis committee met on August 19, and the first water samples were collected.

Eleven samples were taken in total. Three samples from the public water supply were clean, while seven of the eight samples from private wells were contaminated with E. coli.

Authorities examined several possible causes, including on-site wastewater systems and holding tanks, the potential impact of construction work on Rauna Street, and soil samples from risk locations. Deficiencies were found in on-site wastewater systems on several properties, but none could be identified as the cause of contamination in the area’s wells.

Repeat samples taken on September 2 showed that coliform bacteria levels had fallen in several wells. This indicated that the situation was improving but did not establish where the contamination had originated.

On September 2, the Environmental Research Centre collected 10 soil samples from five locations on behalf of Saue municipality and the Environmental Board. The results did not point to a specific source of contamination.

The Environmental Board also investigated a report that a sewer pipe had leaked on Rauna Street during construction. The municipality said that minor leaks may have occurred during the reconstruction of property-specific pipelines, but their scale was not sufficient to cause widespread groundwater contamination. Soil samples taken from Rauna Street supported this assessment.

Camera inspections of AS Tallinna Vesi pipelines in the area also found no broken pipes. The municipality said it would continue spot checks of well water in the affected area.