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Green Line Infrastructure

A Saint Paul Conservation Journey

The light-rail transit 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 water conservation 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 Challenge

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.

“The Green Line infrastructure improvements show what’s possible when cities, regional planning authorities and watershed districts come together with a single purpose – conserving water and protecting our lakes and rivers. Now, for thousands of light rail riders each day, there’s greater visibility for water-related improvements and a deeper understanding of how and why water conservation is important for everyone.” – Forrest Kelley, Regulatory Division Manager for Capitol Region Watershed District.

The Solution

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.

The total cost of the project was approximately $5,000,000 and was covered by a variety of funding sources including a State Clean Water Fund Grant of $665,000 and cash and in-kind contributions from CRWD, Metropolitan Council, and the City of Saint Paul.

Results

It is estimated that the Green Line project will reduce stormwater runoff by more than 50 percent and remove 80 pounds of phosphorus and 40,000 pounds of sediment annually. Additionally, thousands of riders each day interact with the District’s interpretive signage near the practices along the line, which describe the improvements and explain their importance in English, Spanish and Hmong. The addition of tree trenches, rain gardens and other vegetation to the project has a significant impact on climate change, reducing the urban heat island effect, improving air quality and protecting pollinator habitats.

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