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BPDA releases draft zoning overlay to strengthen requirements to prepare new development and retrofits for future climate risks

Jan 04, 2021

Fulfilling steps outlined in Mayor Martin J. Walsh’s Climate Ready Boston, the Boston Planning & Development Agency (BPDA) has released a draft zoning overlay that will require new development and retrofits to take additional steps to limit the damage and displacement related to the impacts of coastal storms and sea level rise. The zoning overlay will promote resilient planning and design, provide consistent standards for the review of projects, and maximize the benefits of investments in coastal resilience. 

“In order for Boston to grow and thrive for generations to come, we must make sure that what we are building today is resilient and protected from impacts of climate change,” said BPDA Director Brian Golden. “By updating our zoning code, we are strengthening our tools to protect our city and our shoreline, and following through on the steps outlined in Mayor Walsh’s Climate Ready Boston.”

The Coastal Flood Resilience Zoning Overlay District will apply to areas of the City that could be inundated during a major coastal storm event, known as a 1 percent chance flood event, with 40-inches of sea level rise. Based upon climate modeling, 40-inches of sea level rise is expected between 2070 and 2100, which is within the usable life of most buildings currently undergoing BPDA review. The 40-inch inundation area is integrated into the BPDA Zoning Viewer

All development projects subject to BPDA’s Article 80 Large and Small Project review will be required to undergo Resilience Review, and comply with the Coastal Flood Resilience Design Guidelines. In 2019, the BPDA adopted Coastal Flood Resilience Design Guidelines to provide clear strategies and best practices for developers, business owners, and residents to respond to climate change.  Earlier this year, the American Planning Association (APA) Sustainable Communities Division awarded the BPDA’s Coastal Flood Resilience Design Guidelines with the 2020 APA Excellence in Sustainability Award in the Policy, Law or Tool category.

The Zoning Overlay (Article 25A of the Boston Zoning Code) will provide new definitions and standards for building dimensions and uses to facilitate flood resilient design for new projects and building retrofits. Intended to prevent flood damage by elevating building occupiable space, flood proofing areas beneath flood elevations, and promoting health and safety by preventing uses such as living space below the flood elevation, the specific provisions of the overlay include:

  • Building Height: Projects undergoing Resilience Review will have their height measured from two feet above the Sea Level Rise Base Flood Elevation (SLR-BFE), rather than at grade, which is what current zoning requires.
  • Building Setbacks: Projects will have allowances to extend into side yard, rear yard, and front yard setbacks for structures needed for vertical circulation, such as stairs or ramps to get from surrounding grade to a higher first floor elevation. There are also allowances for side yard and rear yard encroachments for new structures to house mechanical systems to ensure they are not located in basements or beneath the Sea Level Rise Design Flood Elevation (SLR-DFE), which consists of the SLR-BFE plus one to two feet based on type of use.
  • Lot Coverage and Required Open Space: The structures needed for vertical circulation and mechanical systems referenced above will be excluded from measurement of lot coverage and open space
  • Gross Square Floor Area: Will exclude structures needed for vertical circulation and areas devoted to flood protection measures.
  • Limitations on Use Below the Sea Level Rise Design Flood Elevation: For health and safety purposes, uses beneath the SLR DFE are limited to access or vertical circulation structures; flood prevention measures, storage, and parking accessory to non-residential uses.

The BPDA will host virtual public meetings on January 13 and January 15 to discuss and answer questions on the Zoning Overlay District. The public will have until February 12, 2021 to submit feedback. 
The BPDA has also launched the Zero Net Carbon Building Zoning Initiative to assess and identify strategies to strengthen green building zoning requirements to a zero net carbon standard for new construction, to meet Mayor Walsh’s goal for Boston to be carbon neutral by 2050. 

Mayor Walsh’s 2016 Climate Ready Boston report assessed Boston's climate projections and vulnerabilities to climate change, and identified city-wide strategies for reducing vulnerability to sea-level rise, extreme heat, and intense precipitation. The Climate Ready Boston program that followed the report is led by the City of Boston's Environment Department and the BPDA,  in collaboration with many City and community partners and the residents of Boston. The city is also continuing with Coastal Resilience Solutions reports to address eight vulnerable neighborhoods identified in the 2016 report, and follow studies for East Boston, Charlestown, South Boston, and the Moakley Park Vision Plan to incorporate climate resiliency design to address the threat of coastal flooding and storm surge. Resilient solutions identified through Climate Ready Boston are part of and strengthen the strategies outlined in Resilient Boston Harbor to increase access and open space throughout Boston's 47-mile shoreline while better protecting the City.

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