San Francisco’s trouble with tunnels continues this week. The Municipal Transportation Agency has revealed issues with the Twin Peaks Tunnel, which was completed two years ago, and the fix will be expensive.
The 2-mile-long tunnel project consisted of seismic retrofitting and the replacement of rails, ties and ballast rock. However, it was decided that the contractor would reuse the old ballast of the 100-year-old tunnel, a decision that went against the project contract. To make matters worse, the ballast was not cleaned, and now there is more mud than rock serving as the track bed.
According to Muni Supervisor Rafael Mandelman, the reason the contractor left the ballast in place was due to a higher level of heavy metals found in the rock. It made the process of disposing or handling the ballast more expensive.
Tom Maguire, Muni’s director of sustainable streets, says the decision was a joint one made by the contractor and agency staff.
Inspections have determined that track stability issues are prone to happen at one particular location on the east half of the tunnel. The cost to address the problem will run in the tens of millions of dollars. Muni officials have not determined a timeline for the reconstruction.