The light-rail transit (LRT) Green Line links Downtown Minneapolis with Downtown Saint Paul along the University Avenue corridor. This long-awaited Metro Transit LRT line was first proposed during the 1990s, with construction beginning in 2010.
Green Line construction was a perfect opportunity for CRWD to build green infrastructure practices along the route to help control flooding, manage runoff and improve water quality. With eleven Green Line green infrastructure projects along the route, CRWD sought to connect a variety of sustainable stormwater management features, with the goal of treating stormwater, educating the public and adding beauty to University Avenue. Project partners included the Metropolitan Council, City of Saint Paul and Ramsey County.
The $1 billion, 11-mile Green Line project had several unique challenges. First, the linear tract of land offered limited space for green infrastructure improvements. There were also numerous above- and below-ground utilities, as well as contaminated soils, that complicated the process Finally, a limited budget for the project forced CRWD and its partners to get creative with green infrastructure practices.
CRWD and its partners used four types of Best Management Practices (BMPs) to improve water quality and control runoff volume along the Green Line. First, CRWD constructed rain gardens and stormwater planters in the boulevard on nearby side streets. Rain gardens and planters help control erosion and filter stormwater runoff, in addition to beautifying neighborhoods, while helping stormwater soak into the ground instead of flowing into the storm sewer.
The City of Saint Paul built infiltration trenches on two side streets. An infiltration trench helps stormwater runoff (and the pollutants it carries) soak into the ground, filtering out impurities before entering the storm sewer. Finally, the Metropolitan Council created more than five miles of tree trench and planted more than 1,000 trees on both sides of University Avenue. Tree trenches are built adjacent to storm drains and include permeable surfaces that draw stormwater down into the ground.