The T is already spending more money every year repairing storm damage and that's even before we get hit by something like Hurricane Sandy - or worse - in the coming decades according to a study published last week.
The report, by Michael Martello and Andrew Whittle in Communications Earth and Environment, paints a grim worst-case picture that would make the 1996 Muddy River flooding that shut Kenmore station for several weeks look minor: In the worst case, in a "100-year-storm," a rising Boston Harbor would pour into the T, starting at Aquarium, and flood all four subway lines and the Silver Line tunnel downtown with corrosive salt water, up to a depth of 15 feet, causing billions of dollars of damage in addition to the flooding along low-lying stretches of the T, such as almost all of the Blue Line in East Boston and Revere.
The authors caution, however, that the worst-case scenario assumes no new mitigation effects are in place before a Sandy-like storm hits.
In February, the BPDA agreed to spend $880,000 to study ways of fortifying Long Wharf, under which the Aquarium station largely sits, against rising sea levels, both to protect the historic wharf and to keep it from becoming a flood gateway to the rest of downtown. The city is also in various stages of planning for heading off future catastrophic inundations, through everything from turning parks into sort of giant sponges to sop up water to possibly building a flood barrier across Fort Point Channel. And the Army Corps of Engineers, which has proposed a $52 billion system to protect New York City, says it will begin looking at Boston as well.
Their report estimates that the MBTA's costs for dealing with just today's flooding issues has doubled since 2008, to $24.4 million a year and will likely more than double again by 2030. They detail would could happen in a "100-year storm," similar to what happened in New York when Sandy hit:
Here, we observe widespread flooding throughout Greater Boston, with inundation along the entirety of the Blue Line, significant portions of the Orange, Red, and Silver Lines, and at critical rail maintenance facilities along the Orange, Blue, and Red Lines. The results ... show widespread flooding along the at-grade portions of the system with significant volumes of inflow into underground portions of the system, primarily through tunnel portals, that generate inflows one order of magnitude greater than other ingress pathways at transit stations (e.g., station entrances, ventilation shafts, etc.). The analyses show widespread flooding throughout the underground portions of the system in Downtown Boston, due to the interconnected nature of the underground space that allows floodwaters to inundate adjacent lines in the system. ... Here, we expect flood depths exceeding 5 m [roughly 15 feet] along the majority of the Red, Orange, Blue, and Silver Line tunnels reaching to the crown of the running tunnels. At this level of saltwater inundation, we expect most linear assets (i.e., rail, signals, power, lighting) and stations to sustain damages equivalent to at least 75% of replacement cost.
Considering the projected extent and severity of saltwater inundation across the entirety of the system, we estimate $5.3B (2020 USD) in direct flood damages to the MBTA rail rapid transit system, with expected losses of ~$1.2B to the Red, Blue, and Orange Lines. ... We further observe that damage to connecting stations (i.e., stations where passengers can transfer) are expected to contribute $1.4B in flood losses, a greater proportion than any single line in isolation. We note the significant uncertainty in transit station replacement cost estimates largely informs uncertainty in station flood damage cost estimates, as well as uncertainty in overall flood damage estimates.