Werner Sprung greeted us in his office at 9 am. Two plates of pastries, a jar of water taken directly from the groundwater, and an espresso. The onsite lab at Holding Graz tests the groundwater daily for pollutants. The site is a water protection area. The building is new, compartmentalized with electronically locked doors and nearly no overhead lights required. Floor to ceiling windows illuminated the hallways. A modest two stories but thoughtfully laid out with a parking garage partially below ground level.
Before we began filming Werner stated that he trusted we wouldn't use the video for the Green Party, who would rather "throw Molotov cocktails" at him. I assured him that my interest was artistic and not propagandistic and that, while I intended to express the concerns of members of the activist group, my aim was to show the ZSK as an urban design project. I was transparent about my intention to ask him about the protest during the interview and he agreed.
Sprung showed us a presentation of the Zentraler Speicherkanal on powerpoint that included the profile of the city and the sewer system. The extent of the catchment area, the age and history of the sewer system. The statistics that he drew out, one of which was repeated, was that the combined sewer overflow would reduce 70% of the untreated wastewater entering the Mur. Prior to the ZSK only 30% of the combined sewer overflow is treated when there was rainfall. A few minutes into the presentation I realized that the only thing more mind-numbing than a powerpoint presentation is a powerpoint presentation on video. It’s not the content nor presenter, it’s the format. The audio into the C100 had reset to microphone rather than XLR when I unplugged it for transport and most of the footage was unusable. Amateur mistake.
The rainwater diversion was a motivating factor that I had heard again and again. But the benefits of the ZSK were not just reducing untreated wastewater entering the river, but the additional storage that would allow for Holding Graz to clean and renovate the existing sewers, some of which are over a century old. Currently, in order to renovate sewers, a line would be closed and the wastewater would be diverted to the Mur, increasing contamination.
The origin of the sewers in Graz followed a deadly flood in 1880 (1860?), the creeks were covered to reduce flooding; subsequently the pipes of homes were connected to the covered creeks. The idea of connected a rainwater runoff to the existing covered creeks was to wash away the smell that accumulated in the sewers.
Werner's response to the protest was that he could not understand why anyone would be against the improvement of the water quality of the Mur. He described how brown streaks can be seen on either side of the Mur during rainy days, and how anything, even bicycles, can be found in a sewer. He laughed at the suggestion of ignoring the organic waste that entered the Mur because fish liked it. His role at Holding Graz was system optimization. It was in his essay that I had first learned about the ZSK.
After the presentation, Sprung offered to show us the wastewater treatment plant.
The great thing about a city employee is they usually know a lot about random information about the built environment that would be otherwise difficult to obtain. While visiting the Schloßberg I had noticed that buildings in Graz are almost uniformly capped at four stories. The explanation, Sprung said, was that the building regulation was informed by the air quality concern for stagnating pollution that is typical for the geographic location of a city at the base of a mountain range. That is, the concern for the tiny particulate matter that the tree defenders were describing was already inscribed into the city code. But if growth was underway and height is capped, then the result is sprawl.
We passed through a 10 km long tunnel, part of the freeway that passed under the city. The design of this tunnel, Sprung noted, was a compromise between planners who wanted to add a freeway through the city and opposition that worried about the effects of automotive amputation. (It reminded me of an alternate universe in which Robert Moses’ Cross-Bronx Expressway had been designed with an iota of compassion for community.) Fortunately, tunneling is a specialty of the Austrians, and can be seen in the Schloßberg tunnels, which were used as bomb shelters in WWII. Under the Graz Hauptbahnhof there are tunneled wine cellars, no longer in use, and of course the sewer and combined sewage overflow, which are also tunnels, though constructed differently than the technique Sprung described, that is produced through the use of explosives, allowing the surrounding rock to collapse to a certain distance to increase the load pressure, like a keystone arch, before being reinforced with metal and then covered in cement. The Montanuniversitaet Leoben is one of the institutions that specialize in this peculiar form of engineering.
At the treatment plant, Werner walked us through the stages of purification, from untreated water to initial solid suspension and separation, large and small sand and gravel, bacterial treatment in anaerobic digesters (which predate New York’s Newtown Creek facility by three decades), into another holding tank and out to the final stage before being sent into the Mur. The water isn’t potable, but there are plans to implement higher purification, such as pharmaceuticals, in the coming decade. I asked Sprung about the impetus to create the wastewater treatment plant, whether the European Union Wastewater Framework directive included mandatory renovation of the sewer system. It did not, he answered, because such a directive could not be enforced across the continent, due to a lack of funding. We saw only two other people while on the tour; most of the processes in the plant must be automated.