Skip to Content Skip to Left Navigation
Water Sense
Urban Water Sustainability Council
Sewer Rehabilitation

The Central Metropolitan Interceptor Sewer (MIS) Improvement Project is a $300 million effort that will add another 50 years of service life to some older MMSD sewers without tearing up major sections of busy streets. 
<><><><><><>
Before and After
Over time, sewer surfaces become rough and jagged as sediment and deposits build up on the walls. Uneven surfaces slow flow down causing additional buildup.  Rehabbed sewers have smooth surfaces created from a cured-in-place liner that hardens like fiberglass. 

The project involves about 50 miles of MMSD sewers, 70 to 115 years old, that collect wastewater from hundreds of smaller local sewers throughout an area of Milwaukee that extends roughly between Capitol Drive on the north, south to Cleveland avenue, and west to 43rd Street These sewers carry 60 percent of the District's wastewater, serving 14 of our 28 communities.  

Prior to the Deep Tunnel, we were never able to clean or inspect these sewers because of their high flow volumes.  When the Deep Tunnel went on line, it gave us the ability to divert wastewater from MMSD sewers and store it in the tunnel.  Only then could workers inspect, clean and rehabilitate the sewers.

Technology, planning keep project ‘almost invisible'

Few people on the street even realize this massive project is underway beneath some of the busiest streets and intersections in the metropolitan area.  The use of trenchless technologies and a competitive bidding process are also saving District taxpayers tens of millions of dollars.
<><><><><><>
Cured-in-place lining uses a felt liner and resin to create a new, smooth pipe inside the existing sewer.  Liner segments are fed into the sewer through a manhole (left).  The tube is inverted as it's inserted into the sewer, exposing the resin to the walls of the sewer.  Once the liner is in place, it's filled with water to expand it to the size of the existing sewer. The water is heated (right) to activate the resin and create a bond between the liner and the sewer that will provide an estimated service life of 50 years.