LOOK: Underground work, overwhelming images

More than 3 million pounds of mammoth machinery and she's a thing of beauty.

Last year marked a major milestone in our Project Clean Lake program as tunnel boring machine Mackenzie finished digging the Euclid Creek Tunnel, an 18,000-foot tunnel 200 feet under Cleveland and Lake Erie that will help reduce pollution in our Great Lake by more than 60 million gallons per year.

These are just some of our favorite images from the last 365 days of ECT construction, some coming even after the drilling was complete in August. The project still has more than a year ahead of it as it's not scheduled for completion until 2015.

Project Clean Lake has even more work ahead. It's a 25-year program that will prevent billions and billions of gallons of pollution from entering Lake Erie. It includes a wild combination of seven huge tunnels, as well as green infrastructure projects that will help reduce the amount of stormwater entering the sewer system.

Right now, about 4 billion gallons of combined sewage—sewage and wastewater—are discharged to our Great Lake every year as a result of an antiquated sewer system. By 2035, that amount will be reduced to less than 450 million gallons as a result of Project Clean Lake.