Brussels has an unusual reason for being slow to repair its infrastructure: city officials claim mice ate the plans. The Belgian capital has the worst traffic in Europe, and plans to spend more than $575 million on what one local news site describes as “urgent repairs” to road tunnels over the next few years.

Unfortunately, the city’s ability to fix its major underground thoroughfares—some of which are literally falling apart—has been hampered by the fact that the original plans were chewed through by rodents decades ago, as CityLab reports.

During a meeting last week about the city’s road tunnel issues, former officials from the traffic agency Mobiel Brussels admitted that in the 1990s, a creative storage solution ruined most of the master plans for bridges and tunnels in Brussels.

In the ‘90s, Mobiel Brussels was temporarily housed in a hotel room, and there wasn’t enough space for archived documents like, say, master plans. So the agency stuffed its bridge- and tunnel-related paperwork into the pillars holding up a highway viaduct.

As one might expect, the underside of a bridge is not the best place to keep an archive of important documents. Most of the documents were destroyed or at least significantly damaged by rodents. A host of Belgian mice probably have nice little nests made out of shredded blueprints.

Brussels civil servants clearly need a crash-course in archival science.

[h/t CityLab]