Green Line Green Infrastructure Practices – Water Quality


Green Infrastructure Definition: 
A stormwater management approach that utilizes natural landscape features and hydrologic processes to treat stormwater by infiltrating, evapotranspiring, and/or reusing runoff. Green infrastructure also achieves other environmental goals such as carbon sequestration, reductions in urban heat island effect, improved air quality,

improved wildlife habitat and increased opportunities for outdoor recreation.

FB_train and tree trench     OLYMPUS DIGITAL CAMERA 

The Project
Metropolitan Council constructed the Green Line, a two-way commuter rail system from downtown Minneapolis to Downtown Saint Paul. The Green Line enters the western boundary of the City of Saint Paul, Ramsey County, and CRWD on University Avenue, continuing to the Capitol Grounds, through downtown Saint Paul, and  ending at the Green Line Operations Facility in the Lowertown neighborhood of Saint Paul. Green Line trains will begin running in 2014.The construction of the Green Line was an opportunity to build and demonstrate stormwater BMPs in a highly urbanized area along a large linear tract of land. Construction of the eleven green infrastructure projects began in spring of 2011. The projects were installed along University Avenue and adjacent streets along portions of the light rail running through Saint Paul. The drainage area is 111 acres of highly developed land with large tracts of industrial, commercial and residential areas. The percentage of impervious surface is high in this area, so large amounts of polluted rainwater flows to the storm drain system and ultimately the Mississippi River. Four types of practices are used to improve water quality and control runoff volume along the project area:

  • Rain gardens were constructed in the boulevard on four side streets by CRWD;
  • Five side streets have stormwater planters in the boulevard constructed by CRWD.
  • Two side streets have infiltration trenches constructed by the City of Saint Paul.
  • More than five miles of tree trench with over 1,000 trees was constructed by Metropolitan Council on both sides of University Avenue in Saint Paul.

It is estimated that the project reduces stormwater runoff by more than 50% and removes 80 pounds of phosphorus and 40,000 pounds of sediment annually. Wow!

Project partners
Metropolitan Council
Ramsey County
City of Saint Paul

Project Funding
Minnesota Clean Water Legacy Fund
Metropolitan Council
City of Saint Paul

Construction details
Construction of the tree trench began in spring 2011 starting on the western end of the train corridor. Construction of the other green infrastructure projects coincided with the construction of the rail line. The first side street green infrastructure practice was constructed in September 2011 — the Aldine Street Stormwater Planter – and all projects were complete in summer 2012.

All projects were inspected during construction to ensure proper installation, and temporary erosion and sediment controls were maintained to prevent polluted runoff flowing to the newly constructed BMPs and the Mississippi River.  CRWD has installed monitoring equipment to assess the performance of these projects and data collection from the sites began in .

Public Education and Outreach
With ridership rates estimated at 42,000 trips per day by 2030, there is tremendous opportunity for public education regarding the importance of sustainable stormwater management in urban areas. Interpretive signage has been installed to describe the purpose and function of the clean water projects. The signage has been translated into Hmong and Spanish.

Click for a  printable pdf of the Green Line Brochure
Interpretive Signs of Green Infrastructure Features on the Green Line

raingarden tree trench infiltration trench stormwater planter
Raingarden Tree Trench Underground Infiltration
Stormwater Planter
Jardines de lluvia Zanja de árboles Zanja de infiltración
Jardineras de agua
Vaj dej nag Kab ciav ntoo Kab qhov av xau Thaj chaw nroj tsuag
rau dej nag

Project Funding
The total cost of the project is approx. $5,000,000 and is 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.

Metropolitan Council’s Central Corridor Light Rail Transit Website
City of Saint Paul’s Green Line Website Information
MN Clean Water Fund
US EPA’s Green Infrastructure Website