The developers of the proposed Suffolk Downs project can't stop the tides, so they're planning their massive project to roll with the punches as rising sea levels increase the odds the low-lying site on the East Boston/Revere line will flood on a more regular basis.
In a recent presentation to the Boston Civic Design Commission, HYM Investment Group focused attention on steps to help the massive development - some 10,000 housing units, two malls and numerous office buildings - weather climate change. These include garages designed to hold flood waters on their lower levels during storms, other underground water-retention basins, a "tide gate" to block waters from the neighboring Belle Isle inlet and long green spaces that would double as water channels during flooding.
As part of construction - which could take 20 years before the entire project is finished - HYM is also looking at bringing in fill to raise the first floors of some buildings above the level of anticipated floods.
Many of the ground-level features would have double uses, one for dry times, one for days with flooding. For example, HYM is proposing an outdoor performance area that could hold nearly 300,000 cubic feet (roughly 2.2 million gallons) of water during flooding, to a depth of 17 feet:
HYM says the primary flooding threat would come from Belle Isle Marsh and inlet just across Bennington Street from its 161-acre site - which it hopes to stem in part with a flood gate on its side of Bennington. But the company says in bad enough conditions, the site could also expect inundation from Chelsea Creek and even just from the open ocean swamping Revere Beach and continuing inland.
In addition to the steps it's taking, HYM says Boston, Revere and the state should consider several measures that would protect not only the Suffolk Downs land, but all the residents - and the tank farm - that also surround the site, including a berm along Chelsea Creek and a large berm on the Belle Isle side of Bennington Street that could double as dedicated bike lanes in drier weather.
Proposed Suffolk Downs underground retention system and possible city or state berms:
Look at that swale:
Complete HYM presentation to BCDC (116M PDF).