MWRA: Old water tunnels in poor condition
Can't be repaired without shutting them down
STATE HOUSE NEWS SERVICE
CAST IRON AND STEEL PIPES and valves integral to the tunnel system that provides 60 percent of the water to eastern Massachusetts communities served by the Massachusetts Water Resources Authority are in such poor condition that the system’s overseers have avoided engaging them due to fears of a catastrophic failure.
Authority officials have been aware of the system’s problems for years and now appear poised to try to reach agreement this year or in early 2017 on long-term plans to create redundant water flow systems that would enable them to address the infrastructure vulnerabilities associated with tunnel networks that are 46, 53 and 66 years old and run beneath communities just north and south of downtown Boston.
“They need to be maintained and right now we have no ability to bring the tunnels down to maintain them,” MWRA Executive Director Fred Laskey told the News Service in an interview Wednesday afternoon. “If something went wrong and there was a leak that developed, it would be catastrophic.”
The system’s three Metropolitan Tunnels are the 5.4-mile City Tunnel, built in 1950 and running from Weston under Newton to Chestnut Hill; the 7-mile City Tunnel Extension, built in 1963 and running under Brighton, Cambridge, Somerville, and Medford to the Malden line; and the 6.4-mile Dorchester Tunnel, which was built in 1976 and stretches from Chestnut Hill under Brookline to Morton Avenue in Dorchester. The three tunnels come together at Shaft 7 at Chestnut Hill.
According to MWRA documents reviewed by the News Service, authority officials believe there is a “low risk of failure” in the concrete-lined, deep rock tunnels and concrete vertical shafts that link the tunnels to the surface. The tunnels and shafts require little or no maintenance. The shafts are located in Weston, Chestnut Hill, Allston, Somerville, Malden, West Roxbury, and Dorchester.
However, many of the pipes and valves at the top of each shaft, which are accessed through subterranean vaults and connect to surface pipe networks, have long since passed their life expectancy estimates and are in “poor condition,” according to the authority. Officials are unable to even inspect the aging equipment without shutting the system down, which is not an option due to the lack of a redundant system to keep water flowing to residents and businesses in eastern Massachusetts.
“Valve reliability for the Metropolitan Tunnels is a concern,” authority officials wrote in documents that MWRA Board members have been reviewing in anticipation of a meeting Thursday morning in Marlborough devoted entirely to the situation. “These valves can cut off a majority of the system’s capacity to supply water and due to the physical condition, age, and environment in which they are installed they have not been exercised for fear of breaking them in a closed position.”
The City Tunnel and the City Tunnel Extension were constructed with valve-based dewatering provisions aimed at allowing for the removal of the tunnels from service for inspection or repairs. But in two shafts, both roughly 375 feet below ground, authority officials are unsure whether the valves are in the open or closed position and whether the exposed piping is pressurized and “live” or not, according to authority documents. One chamber “is completely under water and has been submerged for decades.” At the end of the City Tunnel Extension, officials are unsure about the condition of pipe couplings and bolts between tunnel isolation valves and the top of the shaft. “Staff are hesitant to dig up this section as disturbing the pipe could lead to a failure which would require shutting down the tunnel,” officials wrote in documents on the status of the tunnel systems.
According to the authority, “all the potential failure points cannot be mitigated or addressed without tunnel isolation and complete replacement or maintenance of failed or failing components at some point in the future.”
Authority staff have explored 30 options for tunnel redundancy and are recommending a “preferred alternative” to the board. The alternative calls for a new 4.5-mile northern tunnel from Weston under Waltham to the Belmont line. A new 9.5-mile southern tunnel would run from Weston under Newton and Brookline to Lower Mills in Dorchester.
Interim improvements could “bridge the gap” to the long-term plan. Authority staff prefer what they call the “all-tunnel redundancy alternative” featuring two new deep rock, 10-foot diameter tunnels beginning in Weston near the Massachusetts Turnpike/Route 128 Interchange.
The estimated midpoint cost of the northern tunnel is $472 million; the midpoint of the southern tunnel: $1 billion. The combined $1.475 billion cost of the tunnels corresponds to an estimated 17-year construction schedule and includes allowances for a 30 percent contingency and 4 percent annual construction cost escalation. Staff is recommending that work start first on the northern tunnel.
The authority recently marked its 30-year anniversary and its work over that time has focused on infrastructure needed to ensure the cleanup of Boston Harbor, metropolitan Boston area beaches, and the Charles River, as well as bringing water and sewer infrastructure into compliance with federal drinking and clean water laws.
“Now that we’ve come out the other end of that it’s clear that we have some glaring weaknesses in our water systems,” Laskey said. “In particular we have a real lack of redundancy, which really can prove to be a dangerous situation.”
In 2010, about 2 million eastern Massachusetts residents were ordered to boil their drinking water after an MWRA pipe breach in Weston disrupted the supply coming toward Boston, and sent 8 million gallons per hour into the Charles River. Recalling the three-day crisis that ensued, Laskey speculated about the economic and public health impacts that would result if one of the tunnel systems in need of repairs failed and was offline for weeks or months. “It would be horrific,” he said.
Business losses of approximately $200 million per day are expected for a “total water loss event” associated with tunnel failure, with an additional $100 million per day in losses for residents, according to staff estimates.Laskey said he does not expect the MWRA Board to reach a decision on a course of action when it meets to focus on the issue Thursday morning in Marlborough. However, he said he hopes the board can agree on a plan by the end of 2016 or in early 2017.
“It’s an important strategic decision,” he said. “It has a major impact on the Commonwealth and the cities and towns that are going to pay the freight.”