This summer, two dangerous storms passed through the Bolesławiec municipality and city. The first occurred on June 25, and the second on the night of July 29–30. Both caused flooding. During the second storm, 80 liters of water fell per square meter.
The problem was that the sewer system was designed according to generally accepted standards and can handle such heavy rainfall for no longer than 15 minutes. On the night of the storm, the heavy rain lasted an hour and a half.
“No sewer system in the world is capable of taking in that much water,” explains Grzegorz Kozłowski, technical director at PWiK. “And we were still lucky, because the storm’s epicenter was in Leśna. The entire city there was flooded, along with the water intakes and treatment plant. Those facilities remained out of operation for a long time,” the director adds.
PWiK is responsible for removing flooding caused by the sewer system. Flooding from other sources is handled by the State Fire Service. On that fateful night, all available PWiK forces were sent to deal with reported flooding.
“All available equipment was sent into the city,” says Józef Król. “After the operation, we received several messages of thanks for our quick response and arrival at the scene. After the downpours, we also investigated the causes of the flooding and advised affected residents on how to protect themselves against damage in the future. In this case, the simplest and most effective solution is to install backflow prevention valves,” Król adds.
Besides the extreme rainfall, which had never previously been recorded in our area, the causes of flooding outside the city should be sought in the lack of maintenance managers for drainage ditches.
“Many of the ditches have been filled in or concreted over,” says Józef Król. “No one maintains them, and during such downpours the water has nowhere to flow. Ceramiczna Street, which is flooded from the direction of the fields, is one example. A separate problem is the sewer network in the municipality, which was designed and built solely as a sanitary sewer system. If someone illegally connects a roof drain to it, or simply opens a manhole cover while trying to prevent flooding, disaster is inevitable. We had such a situation during the rainfall on June 25 in Łąka. At the time, the sewage pumping station was at risk of flooding. Illegal connections to the sewer system are punishable by heavy fines of up to 10,000 zlotys, including imprisonment. We conduct systematic inspections in this area, and following the recent events, we will be forced to report such cases to the police,” adds the PWiK president.
In the city, the situation is different: rainwater from roofs and yards may be discharged into the sewer system. The sewer network is capable of receiving it, except, of course, in such extreme circumstances as the rainfall on the night of July 29–30.
“It is worth mentioning on this occasion that the sewer network is technically sound, systematically inspected and cleaned when necessary,” says Grzegorz Kozłowski. “The problem, however, is the street inlets, commonly called manholes, which are the responsibility of road administrators. The inlets should be cleaned regularly and kept continuously clear. Our company has an agreement with the District Office in this area, but it includes a clause stating that we clean the inlets upon request—unfortunately, in most cases only after they have become completely clogged with sand and gravel. Ideally, they should be cleaned twice a year,” the director adds.
(information: ii)