|27th St. Deep Tunnel Extension
A piercing air horn cuts the spring air, signaling people in the immediate area that a controlled blast is about to occur 300 feet underground in this Milwaukee neighborhood at 31st Street and Hampton Avenue.
Someone yells, Fire in the hole.”
Within seconds, a series of concussions rise up from below, the sound waves rattling nearby windows.
The horn blares one more time signaling the all clear.
It's a familiar scene for the miners who do this type of work for a living. Dressed in rain gear and safety equipment, they ride an enclosed cage hooked to the end of a crane to their office” deep under the earth.
There, the workers use a bulldozer to move the pieces of bedrock that they blasted out and the muck,” as they call it, is lifted out of the hole by the same powerful crane that lowered them into the shaft.
Workers use controlled blasting to carve out a starter tunnel for the massive tunnel boring machine that will drill a two-mile long extension to the Milwaukee Metropolitan Sewerage District's (MMSD) Deep Tunnel system.
The tunnel boring machine needs a special electric line to energize its motors that, at maximum output, use enough electricity to power 2,300 homes.
It's hundreds of feet long and equipped with a 23-foot diameter cutting head. About 35 semi trucks will deliver the machine to the job site in pieces.
Part of MMSD's $1 billion Overflow Reduction Plan
The $80 million 27th Street Deep Tunnel is one of many projects aimed at reducing the risk of basement backups for homes and businesses and sewer overflows to Lake Michigan.
Water reclamation facilities can efficiently clean only a certain amount of wastewater a day. When it rains and excess water gets into the sewer system, you need Deep Tunnels to store the extra water until the reclamation facilities have time to handle the extra flows.
MMSD's new Deep Tunnel will connect directly to the existing system, providing an extra 27 million gallons of storage. Upon completion, the District's total Deep Tunnel system will store 521 million gallons, an increase of 28% over the first phase of the system that stores 405 million gallons.
Since its first full year of operation in 1994, the Deep Tunnel has prevented more than 71.5 billion gallons of wastewater from polluting Lake Michigan.