Maple Leaf reservoir dig – enough dirt to land a 777

Two years from now, all this will be under 30 feet of water. Work will have begun on a new park on top, where the waters of the old, open Maple Leaf Reservoir glistened for the past 100 years.

This is the last, and largest, piece of the city’s program to bury four open reservoirs. It’s also by far the most eye-catching (and ear-numbing) project in the neighborhood, perhaps in the city.

Before it’s done, that rising mountain of dirt at the top end of the reservoir will contain 65,000 cubic yards of soil. If it were concrete, there would be enough to build the third runway at Seattle-Tacoma International Airport.  Or to assemble a moon rocket.

The mountain is as high as it will get in this photo (those are the new concrete reservoir walls being built in the foreground). The dirt is being stored on site – and up to its neighbors’ second or third floors – because it would be too expensive to truck away and haul back again, said Duane Narruhn, the project’s construction resident engineer.

Total cost of the finished reservoir – but before building the park – is estimated at $27.4 million plus tax. The park money comes from the Parks and Green Spaces Levy, approved by voters in 2008.

Water will flow into the 60 million-gallon tank from the site’s east end, and exit through a massive “mechanical vault” that’s 30 feet in diameter, said project manager Stephanie Murphy, seen here in front of the vault. Murphy, an engineer, has managed all four buried reservoir projects.

The program to cover the city’s open reservoirs picked up speed after the terrorists attacks of Sept. 11, 2001, heightened security concerns, but has the bonus of creating 76 acres overall of new open and park space, in our case with a prime view of downtown.