After several old buildings at the Milwaukee Regional Medical Center were demolished, an abandoned pedestrian tunnel network was left behind -- along with the potential for security issues, structural failure and unwanted groundwater seepage. Removing the tunnel network was a costly and disruptive proposition. Plus, the owner wanted to maintain the option of re-opening these tunnels in the future. The best solution was to abandon the tunnel in place and fill it with a material that could be easily excavated in the future.

The project consisted of two tunnel sections. The first tunnel connected two recently demolished buildings and was approximately 577 cubic yards, while the second tunnel connected four buildings and was roughly 2500 cubic yards. Original project plans called for filling the tunnel via gravity using as many as eight access shafts, however, MixOnSite was able to provide a more efficient solution using Geofill LD. 

Using this highly pumpable and flowable foam concrete material, MixOnSite filled the entire tunnel complex from just three locations which helped minimize disruption to the hospital services and other construction activities. From these access points, a system of 2” PVC injection pipes were installed along with bulkheads in key locations to assure 100% of the tunnel was filled.

Using our dry mix equipment, MixOnSite produced at a rate of 400 cubic yards per day. Densities ranged from 26 to 30 PCF with strengths of ~50 PSI. Our foam concrete material worked extremely well as a tunnel fill material and will remain easily re-excavatable should the owner choose to access the tunnels in the future.