Zagreb to monitor groundwater near 33,000 tonnes of industrial waste

Zagreb has selected a company to monitor groundwater near a site containing around 33,000 tonnes of hazardous industrial waste, renewing attention on a long-standing environmental issue close to one of the Croatian capital’s drinking water supply areas.

According to Jutarnji list, the City of Zagreb has awarded the monitoring contract to ALS Environmental Croatia, based in Kastav, to measure groundwater levels and assess water quality in the Savica area.

The site is known for the so-called Savica tar pits, where industrial waste has been identified in three lakes near the Petruševec water supply area. The location is particularly sensitive because of concerns about the potential impact of contamination on groundwater.

The presence of hazardous industrial waste at Savica has been documented for years. The site was identified as contaminated with tar, a by-product of industrial processes, and has been included in official city documents addressing the protection of Zagreb’s water sources.

The City of Zagreb’s remediation programme for water-source protection zones identifies contamination at the Savica lakes and recommends systematic monitoring of groundwater levels and quality.

The purpose is to assess whether pollution could affect groundwater flowing towards the Petruševec water supply area and to establish how conditions change over time.

Is Zagreb’s drinking water at risk?

The existence of hazardous waste near a water supply area does not, by itself, establish that drinking water is unsafe.

The Institute for Water Management Josip Juraj Strossmayer said in September that it had been conducting regular groundwater monitoring at 14 measuring stations, or piezometers, in the Petruševec area since 2022. It reported that the chemical status of the monitored groundwater was good in 2025.

Piezometers are monitoring wells used to measure groundwater levels and collect samples for quality testing.

The new contract is intended to provide further information about groundwater conditions around Savica. The latest monitoring results will be important in determining whether contamination is changing and what additional action may be required.

For Zagreb, the priority remains understanding the environmental impact of the historic waste deposits and ensuring that groundwater around the city’s water supply areas is properly monitored.