Planning Board signs off on Avalon Bay open‑space plan beneath Lechmere viaduct with refinements requested

The Cambridge Planning Board on April 15 concluded a design update for PB‑175, the Avalon Bay open‑space and multiuse‑path element at NorthPoint/Lechmere, and asked the applicant to refine some final details before construction. The board voted 7–0 to end the design update and directed staff and the applicant to continue finalizing plantings, material selections and accessibility details.

Background and scope Emily Carmody, vice president of Avalon Bay's capital projects group, said the open‑space and multiuse path work was originally part of a special permit approved in 2015 and amended several times thereafter. Construction of the two residential buildings on the site is complete, she said, but the open‑space and the section of the multiuse path beneath the Green Line viaduct were delayed while MBTA and MassDOT completed the Green Line Extension and Monsignor O'Brien Highway improvements. Avalon Bay and its consultants returned to the board with a refined plan that adapts the earlier design to the as‑built viaduct and roadway alignments.

Key design elements Landscape and design consultants presented a linear open space under the elevated viaduct that includes: - A 12‑foot multiuse path that connects to the parkland and sidewalks to the south and east; the path was adjusted to maintain safe turning radii where it navigates infrastructure supports. - A dog park sized to fit within the narrow strip, with double‑gated access and a low, visually open fence. - Passive seating and sculptural "letter" seating elements intended as gathering/wayfinding features and visual identity for the Lechmere area. - Low‑maintenance hardscape, granite salvaged stone elements and fitness/active elements (outdoor exercise equipment) integrated along the linear plaza beneath the viaduct.

CDD comments and constraints Susanna Bigelow, urban design staff, said staff was "generally very pleased" with the design and the effort to retain the earlier design vocabulary while responding to the changed site constraints. Staff recommended stronger spatial organization to clarify activity zones (for example, grouping fitness equipment and defining edges between the path and the dog park), more planting where feasible along the southern edge and careful attention to permeable paving and irrigation details.

The team explained one core constraint: much of the open area sits beneath the viaduct and will receive limited rainwater and seasonal water; the consultants said they worry that shade‑tolerant plantings could struggle without irrigation and winter watering. For that reason the design favors durable hardscape treatments in the deepest shaded area and concentrates planting in edges where soil and sunlight conditions are more favorable.

Next steps and board action Board members praised the adaptive reuse of the viaduct zone and encouraged additional refinements. Mary Flynn and others urged designers to explore additional small‑scale trees or clustered plantings where possible and to provide more formal definition of the different activity areas. The board voted 7–0 to conclude the design update and directed staff and the applicant to return to continuing review with the items listed in staff comments (final fencing, light fixture specification, planting palette and maintenance/irrigation plan).

Ending Avalon Bay said it has received MBTA review and is close to finalizing the MBTA license needed to construct work within the transit easement. If the remaining procedural items are completed, the team said, work could proceed as scheduled.