The 5,000 pound inspection vehicle was lowered into the tunnel by a crane. Click here to enlarge imageOther challenges for the project included what many would consider the simple task of communicating from the surface to the crew inside the ISS. The contractor did not feel comfortable relying on two-way radio communications. Instead, the crew used three separate modes: a hard-wired phone system; two-way radios; and air horns for backup emergency communications.
The project remained on schedule even though the original timetable did not include the downtime required each day to retrieve the hard-wired phone system. The crew would lay the phone system as it progressed through the tunnel and then take a day to retrieve the phone line before moving on to the next segment.
The inspection project was performed in three phases, with the first measuring the amount of groundwater infiltrated on a daily basis. Phase two consisted of preliminary man-entry at two access shafts to determine tunnel conditions that could be encountered during the full inspection, and the third phase included the manned inspection with videotaping.
Overall, the inspection team was pleased with the safety conditions found inside the ISS. Ventilation and airflow were extremely positive; so much so, it was actually a little windy inside the tunnel, inspectors said.
The ISS is designed to capture excess wet weather flows and prevent sewer overflows to area waterways. Since inception, it has prevented more than 250 overflows and 40 billion gallons of untreated wastewater from entering Milwaukee-area waterways. Before the system went on-line, there were 50 to 60 sewer overflows annually. Since 1994, that average has declined to 2.5 overflows a year.
"This environmental asset has provided tremendous benefits to the community and helped improve the water quality of area rivers and Lake Michigan," Riley said. "Just like going to the doctor or dentist for regular checkups to make sure you're healthy, it was vitally important that we take preventative steps to make sure the ISS is healthy for the next 50 to 75 years for future generations."