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PORTLAND — It’s not hard to enjoy the Bayside neighborhood on a sunny day.
It’s the wet days that should concern residents and city planners, according to the final report of the Bayside Adapts group.
A synopsis of the report presented to the City Council Sustainability & Transportation Committee Oct. 18 estimates the neighborhood between Back Cove and Forest, Cumberland and Washington avenues could experience sea level increase of 2-6 feet by 2100.
Bayside Adapts recommended the city commit to manage sea level increases of 1.5 feet by 2050 and 3.8 feet by 2100. The city should prepare to manage sea level increases of 3.4 feet by 2050 and 8.8 feet by 2100.
Sea level increases could also affect the harbor side of the peninsula along Commercial Street. But at the outset of the Bayside Adapts meetings in December 2016, city Waterfront Coordinator Bill Needelman say Bayside is the more vulnerable area because it is lower than Commercial Street.
“We have a little work to do in the next 100 years,” Councilor Spencer Thibodeau said Oct. 19. “As we are considering buildings and infrastructure, we should not be considering them for 2017 or 2018, but for the impacts of rising sea levels in 2050 and 2100.”
Before 1870, Bayside was largely under water. Debris from the 1866 fire that ravaged the city’s peninsula became fill that extended land into Back Cove, with more fill extending the shoreline in 1900 and 1940.
The worst-case scenario for sea level rise would bring daily high tides back to the pre-fire shoreline, pushing to or beyond Lancaster, Oxford, Fox and Anderson streets.
“Flooding has been a problem in Portland’s Bayside area for decades. The low-lying neighborhood is already susceptible to flooding during high tides. When coupled with heavy rain, these conditions worsen,” the Bayside Adapts report noted.
Bayside Adapts is the first phase of confronting increased sea levels, and its report concluded there is already a good basis of information available for planning. More information is needed on the status of drainage systems, however, even as the city moves ahead with projects to separate mains for stormwater and wastewater.
One ongoing project affects the flow of stormwater and wastewater from Cumberland Avenue and State Street past Deering Oaks Park and along Marginal Way and Preble Street to Back Cove.
A second project planned for the area at the intersection of Franklin Street, Marginal Way and Interstate 295 has been on hold after bids came in $10 million to $15 million above the 2013 estimated cost of $21.5 million.
Bayside Adapts was not the first effort to understand the potential effects rising sea levels; studies date to 2005, and the city was also part of a research project, with South Portland, by the Urban Land Institute.
Bayside Adapts brought together a working group of residents and business owners, then sponsored a design contest last spring to cultivate concepts to make development, commerce, transportation and residential use viable in the area.
The first-place design by Aceto Landscape Architects proposed unearthing Mill Cove, which sat near the Forest Avenue exit on I-295, to handle some water flow, while also rerouting the highway and placing it on a berm. The “Back to the Mill” concept also suggested putting some neighborhood arterial streets underground and using smaller streets to run through mixed development.
The city has already committed to elevating Somerset Street above the flood plain when the Midtown project, which could bring 440 housing units to Bayside, gets underway.
City Manager Jon Jennings has also committed to a wholesale revision of the city’s zoning codes, which Thibodeau said is the chance for the city to regulate development in the face of more sea water.
A worst-case scenario of Bayside sea level rise puts the intersection of Franklin Street and Marginal Way in Portland under daily high tides by 2100.
Bayside Adapts models show sea level rise in the Portland neighborhood could swamp the area that has been filled in since 1870.