With funds earmarked for leak sealing and fire suppression efforts, the state plans to spend $39.4 million in the coming fiscal year on the regional tunnel network left behind after the Big Dig, the unprecedented highway construction project that ran from 1991 until 2006.
The spending projection was included in a $2.2 billion capital spending plan for fiscal 2018, which begins July 1. Gov. Charlie Baker released the plan Thursday, saying it will leverage other public and private funds and lead to total investments exceeding $4 billion.
The capital plan includes limited information about the purpose of the tunnel spending, saying it's for "reconstruction and maintenance the regional tunnel network with state and federal funds along with public-private partnerships."
A Baker administration official provided additional information at the News Service's request.
"Please note that this is referencing investments in routine regular maintenance to the tunnel system, vent buildings and associated equipment within the MHS system," Massachusetts Department of Transportation spokesman Patrick Marvin explained in an email. "Projects include fire standpipe and suppression maintenance and upgrades, routine and emergency maintenance contracts, overhead lighting, leak sealing, pump maintenance and upgrades as well as vent building work."
There are seven major tunnels that are part of the larger 250-mile Metropolitan Highway System in, beneath and around the downtown Boston area. The system includes 227 bridges and viaducts, including the Zakim Bridge, and three of its tunnels — the Ted Williams, Sumner and Callahan -- run under Boston Harbor.
The MHS faces triennial inspections. Here's the 2015 inspection report.