HOUSTON – Under Post Oak Boulevard, and in the shadow of Williams Tower, is a 120-foot-long tunnel dug by hand.

The meticulous work was done by crews installing a 12-inch sewer line as part of the “Boulevard Project.”

The size of the tunnel is only three feet by three feet; requiring special training to work in such a confined space.

“It's the special kind of guy to go in there and do what they do,” said construction superintendent Roman Trevino.

Working 10 hour days, and at a rate of 1 foot an hour, crews used small shovels and spades equipped with air compressors to dig the tunnel. Only two people are allowed in the tunnel at a time; one to dig, the other to transfer the dirt and clay to small rail cart. Trevino said in his 20 years of construction work he has only seen one other tunnel dug by hand.

Dive into the hole at 5pm on #kprc2 Posted by KPRC2 Robert Arnold on Friday, August 4, 2017

“It's muscle is what it takes, a lot of effort to get in there and do what they do,” said Trevino.

Extra fresh air is pumped into the tunnel to make sure crews have plenty of oxygen and each crew only works for two to three hours at a time.

“When you're working a confined area, you're working on your knees, you get cramps and so forth,” said Trevino.

The tunnel is part of a massive project to redevelop Post Oak from Richmond to the loop.

“We're rebuilding the boulevard to make it one of the great boulevards in the United States,” said Bob Ethington, director of research and economic development for Uptown Houston.

Ethington said once the project is complete Post Oak will be widened from 120 feet to 136 feet, sidewalks from 4 to 12 feet, there will be a dedicated bus lane, nearly a thousand live oak trees and flowers planted. Ethington said the improvements were needed to keep up with a booming population.

“The density of this area is going to become more and more dense,” said Ethington.

Hand tunneling was chosen for this part of the project to minimize the amount of street being torn up and heavy equipment snarling traffic, and to cut down on unforeseen problems that typically come with projects using large machines.

“Sometimes we hit things that we just don't know are there and we just don't want to take that chance,” said Ethington.

Trevino said hand tunneling allows a crew to move slowly and avoid cutting utility lines. The entire project is expected to be wrapped up by the end of next year.