Boston aims to help developers plan for rising seas

A rendering shows the South Boston Waterfront with a 7½-foot rise in sea level. Arrowstreet

Mayor Martin J. Walsh wants to make it easier for Boston’s building owners and developers to prepare for future flooding and rising sea levels.

City officials say the mayor has directed the Boston Redevelopment Authority and the city’s environmental services and inspectional services divisions to reduce the red tape involved with building or modifying a structure if it’s for the purpose of making it less prone to flood damage.

In particular, the three city agencies will determine whether it’s OK to raise height restrictions to accommodate putting mechanical systems on a higher floor, or on the roof. To avoid flood damage, electrical and HVAC systems would be located above the ground floor. But that could take away from valuable office or residential space. An extra height allowance could give owners and developers room to make up the difference.

“If we’re working with a project and they want to raise their ground floor or even to plan to raise their ground floor, they’re going to end up having to make up that space somewhere else in the building,” said John Dalzell, a senior architect at the Boston Redevelopment Authority. “It becomes a [financial] barrier because it makes the project less feasible.”

The directive from Walsh is still new — the mayor issued it last week — so it’s unclear what kind of changes will be implemented. The scope of this city effort is still being defined, although it could involve some revamping of city zoning codes.

Among the ideas being considered: measuring the height of a building from the top of a flood-proof level or from the top of an earth berm built to protect the property. In other words, a certain amount of “flood resistant” footage wouldn’t be counted against a building’s height limit.

Some waterfront developers are already considering sea level rise in their designs. Most notable is the new Spaulding Rehabilitation Hospital that opened in the Charlestown Navy Yard two years ago. In that building, the primary electrical operations are on the roof, the ground floor is intentionally 2½ feet above the 500-year flood plain elevation, and the landscaping is designed to serve as a shield to protect against a major storm surge.

But existing buildings could also use the city’s help.

For example, Boston Redevelopment Authority officials have discussed the possibility of moving electrical systems out of the basement at 255 State St., a 12-story office building next to the Boston Harbor Garage. Michael Aalto, a spokesman for the owner, Pembroke Real Estate, said the company wanted to know if it could build more office space on the roof to make up for any space that would be lost to the relocated electrical systems.

Vivien Li, president of the Boston Harbor Association, praised the Walsh administration’s effort, saying it’s important to recognize the need to prepare now for the potential devastation that storm-related surges could bring.

“With so much development happening on the waterfront, you want them to think proactively,” Li said.

The impact of such changes could be seen on properties away from the waterfront, as well.

David Begelfer, chief executive of the real estate trade group NAIOP Massachusetts, said he suspects that the owners of smaller buildings in a flood plain farther from the shore will probably see a bigger benefit than the companies with waterfront towers.

That’s because developers usually get certain height and floor-area exemptions from the city when they build downtown or along the water.

“In reality, when it comes to the major buildings that are built — the proposals that are built in the Back Bay, the Financial District — the height is going to be negotiated anyway,” he said. “This is probably more designed for the smaller projects, or the mid-size type of properties . . . than it is for the large-scale projects.”