Three years after Massachusetts authorities vowed to close all leaks in Boston’s Big Dig underground highway system, it’s still leaking.

In fact, the Boston Globe reports almost 2 million gallons of water flow through one of the tunnels each month – a nearly 20-percent increase over last year’s volume.

The state is now spending about $5 million a year to plug leaks, the Globe reported. One official notes they’re making progress, with only about 800 leaks left compared to more than 3,500 in 2004.