The hundreds of litres of spent oil and diesel that flowed into Lunzjata Valley in Kerċem, as a result of the Good Friday blackout, have been cleaned up and the valley turned to its previous state.
The power failure, which plunged Malta and Gozo into darkness on April 2, also affected a public sewer system which overflowed into the valley.
An estimated 400 litres of oil and diesel, which had been illegally dumped in the sewage system, had to be painstakingly removed manually by Water Services Corporation employees. This oil was released into the watercourse when the pumping station failed.
The Lunzjata Valley, which leads down to Xlendi, forms part of the Wied tal-Kantra Natura 2000 site and is protected under EU regulations because of its ecological importance.
The site hosts species and habitats of national and European importance. The valley itself is home to the only known Gozitan population of the Maltese freshwater crab (Potamon Fluviatile Lanfrancoi), which is endemic to the islands and ever decreasing in density because of a variety of reasons, including habitat degradation.
A Mepa spokesman said the authority put in all its resources and efforts into ensuring that the least possible damage was caused to this ecosystem. It worked in close collaboration with the police, the Water Services Corporation, the Civil Protection Department and Alpha Briggs, a company focusing on emergency response services for the containment and recovery of oil spills.
The oil slick had extended considerably downstream.
Now that the clean-up operation has been concluded, the authority is carrying out in-depth studies to establish the extent of the damage to the watercourse and the plants and animals that depend on it.
A number of specimens of the freshwater cab were noted on site following the clean-up but the status of the population is still unknown and requires further assessment, the spokesman said.
A spokesman for the Water Services Corporation said it was in the process of installing a special "supervisory system" which would detect possible overflows well in advance of them happening. This would enable it to act as soon as a power failure results in a possible overflow of sewage.
Moreover, the spokesman said, the corporation was also looking into installing generating sets with automatic changeover in the coming weeks, enabling pumping stations which end up without power to get it from nearby stations.
The installation of generators at each of the 100 pumping stations across the islands, 13 of which are critical and considered as very important, was not feasible, the spokesman said, since most would end up resembling "mini power stations".