The extensive Emerald Necklace park system is one of Boston’s distinctive urban amenities. Highway expansion beginning in the 1960s severed the system at various points. Today, a broad-based project aims to repair one of the most important and heavily affected sections of parkland.

Project description by jury

The project proposes the reintegration of a roadway and a river through a new green infrastructure that incorporates multi-modal transportation and public recreation. Frederick Law Olmsted’s Emerald Necklace was a pioneering model of urban green infrastructure from the 1880s that has been fragmented by elevated highways built in the last century. This urban operation restores the Charlesgate green area as a critical link in Boston’s regional park system across 1km of new shared-use pathways, over 20km of reconnected greenway and 300m of restored shoreline.

As a Main category prize winner in the regional Holcim Awards 2020, Emerald Gateway in Massachusetts, USA automatically qualified as a finalist in the Global Holcim Awards 2021.

View Global Holcim Awards Entry – Emerald Gateway in Massachusetts

The built environment has a significant role to play in addressing climate change and enabling the transition to a net-zero and more inclusive future. The Holcim Awards for Sustainable Construction global winners showcase the cutting edge of approaches to sustainable design, green architecture, and materials innovation. In the 6th competition cycle, the predominant focus of the entries in the North America region was the sustainable improvement of quality of life. The global prizes were presented at a handover ceremony at the International Architecture Biennale in Venice, Italy. The regional Holcim Awards Main category winners for North America were recognized at the same event.

Sustainability by balancing regional infrastructure with ecology and local urban life 

This project recovers Charlesgate for people and natural systems after it was enshadowed and fractured by elevated roads for a generation. Pathways are designed to double-function for equipment access (lift and vacuum trucks) for viaduct maintenance and repair. Rain-gardens in recreation areas treat roadway runoff, store floodwater and create pollinator habitat. The river's edge is reshaped to protect from floods, and also provide public access and riparian species habitat. The design utilizes standard material palettes of the involved public agencies (transportation, parks and water) in unexpected ways to allow for easy co-maintenance. By integrating considerations of infrastructure, natural systems and public realm, there is sustainability through shared use, maintenance and investment.

• Transportation: Charlesgate restores a critical link in the Emerald Necklace park system lost since the highway era. This link ties together dozens of miles of the most heavily trafficked paths in Boston and nearby communities, significantly improving carbon-free commuting options in the region.
• Water quality: Currently, all nutrient-rich runoff from roadways (25,000m2 of asphalt) around Charlesgate discharge, without treatment, into rivers feeding the Atlantic Ocean. These nutrients cause algae and duckweed blooms, which die off releasing CO2 into the rivers and ocean; and deplete the water of oxygen (eutrophication and ocean acidification). The Charlesgate project routes all runoff into constructed wetlands to eliminate and filter nutrients.