Reshaping Downtown Minneapolis
Looking to reduce traffic congestion while refurbishing its downtown streetscape, the city of Minneapolis, MN, recently completed the first of several major reconstruction projects. The Marquette Avenue and 2nd Avenue (MARQ2) project was the first such effort aimed at reshaping transportation in the Twin Cities. Funded as part of an Urban Partnership Agreement grant, the $37 million project included the complete 24-block renovation of both Marquette and 2nd avenues.
Both streets were rebuilt from building front to building front. Both include two bus and two traffic lanes (four lanes total), new transit shelters, wider sidewalks, more trees, and new landscaping.
Among the many challenges posed during the project was how to mitigate stormwater runoff. “We have long had capacity problems with stormwater management downtown,” says Lois Eberhart, water resources administrator for the city of Minneapolis. “We needed to find a new way of dealing with stormwater.”
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The MARQ2 project was the first
effort aimed at reshaping transportation in the Twin Cities. |
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| The Silva Cell application allows a tree to achieve maximum root growth. |
After hearing about DeepRoot’s Silva Cell system, specifically its ability to catch and filter stormwater runoff while providing maximum soil volume for tree root growth in difficult urban environments, Eberhart invited DeepRoot to make a presentation. Less than two years later, groundbreaking began on the largest Silva Cell project to date, covering 48 linear blocks. In addition to the installation of nearly 11,000 Silva Cell frames supporting 185 trees, the project replaced previously impervious sidewalks with pervious pavement, allowing for greater infiltration and filtration of stormwater within the system.
Each Silva Cell group holds approximately 580 cubic feet (16 cubic meters) of bioretention mix soil and can store 116 cubic feet (3.2 cubic meters) of stormwater. Over the entire project site, that’s nearly 21,600 cubic feet (0.5 acre-feet, or 611 cubic meters) of stormwater storage capability.
The Silva Cells are able to capture and treat the “P” storm, or average storm equivalent, which in Minneapolis includes 90% of rain events (less than or equal to 1.03 inches, or 2.62 centimeters, in a 24-hour period).
“We’ve modeled a 10% reduction in peak flows (peak storm event) to our stormwater system as a result of this installation,” says Bill Fellows, project manager for the city of Minneapolis.
Based upon the data values from research done by Prince George’s County, MD, the filtration offered by the soil within the Silva Cells will remove more than 80% of phosphorous; 60% of nitrogen; and more than 90% of lead, copper, zinc, and iron.
“I’ve seen different products come on the market, but what is infinitely better with Silva Cell is the fact that you actually get much more uncompacted soil volume for the tree roots,” says Chris Behringer, an urban design engineer from SEH Inc., which worked in conjunction with the city on the project. “Unlike structural soil alternatives, the Silva Cell application provides greater filtration benefits while allowing a tree to achieve maximum root growth. Instead of your typical 5- to 10-year lifespan, we’re now hoping for 30 to 40 years, maybe more. And as trees mature and their root systems grow, the filtration capability also improves.”
“This corridor is full of utilities, and there were few possibilities of adding more storage for stormwater,” says Eberhart. “One of the beauties of the Silva Cell system is that existing utilities to a great degree could stay in place. It definitely gave us the best solution.”
March-April 2010
Reshaping Downtown Minneapolis
Looking to reduce traffic congestion while refurbishing its downtown streetscape, the city of Minneapolis, MN, recently completed the first of several major reconstruction projects. The Marquette Avenue and 2nd Avenue (MARQ2) project was the first such effort aimed at reshaping transportation in the Twin Cities. Funded as part of an Urban Partnership Agreement grant, the $37 million project included the complete 24-block renovation of both Marquette and 2nd avenues.
Both streets were rebuilt from building front to building front. Both include two bus and two traffic lanes (four lanes total), new transit shelters, wider sidewalks, more trees, and new landscaping.
Among the many challenges posed during the project was how to mitigate stormwater runoff. “We have long had capacity problems with stormwater management downtown,” says Lois Eberhart, water resources administrator for the city of Minneapolis. “We needed to find a new way of dealing with stormwater.”
|
The MARQ2 project was the first
effort aimed at reshaping transportation in the Twin Cities. |
|
| The Silva Cell application allows a tree to achieve maximum root growth. |
After hearing about DeepRoot’s Silva Cell system, specifically its ability to catch and filter stormwater runoff while providing maximum soil volume for tree root growth in difficult urban environments, Eberhart invited DeepRoot to make a presentation. Less than two years later, groundbreaking began on the largest Silva Cell project to date, covering 48 linear blocks. In addition to the installation of nearly 11,000 Silva Cell frames supporting 185 trees, the project replaced previously impervious sidewalks with pervious pavement, allowing for greater infiltration and filtration of stormwater within the system.
Each Silva Cell group holds approximately 580 cubic feet (16 cubic meters) of bioretention mix soil and can store 116 cubic feet (3.2 cubic meters) of stormwater. Over the entire project site, that’s nearly 21,600 cubic feet (0.5 acre-feet, or 611 cubic meters) of stormwater storage capability.
The Silva Cells are able to capture and treat the “P” storm, or average storm equivalent, which in Minneapolis includes 90% of rain events (less than or equal to 1.03 inches, or 2.62 centimeters, in a 24-hour period).
“We’ve modeled a 10% reduction in peak flows (peak storm event) to our stormwater system as a result of this installation,” says Bill Fellows, project manager for the city of Minneapolis.
Based upon the data values from research done by Prince George’s County, MD, the filtration offered by the soil within the Silva Cells will remove more than 80% of phosphorous; 60% of nitrogen; and more than 90% of lead, copper, zinc, and iron.
“I’ve seen different products come on the market, but what is infinitely better with Silva Cell is the fact that you actually get much more uncompacted soil volume for the tree roots,” says Chris Behringer, an urban design engineer from SEH Inc., which worked in conjunction with the city on the project. “Unlike structural soil alternatives, the Silva Cell application provides greater filtration benefits while allowing a tree to achieve maximum root growth. Instead of your typical 5- to 10-year lifespan, we’re now hoping for 30 to 40 years, maybe more. And as trees mature and their root systems grow, the filtration capability also improves.”
“This corridor is full of utilities, and there were few possibilities of adding more storage for stormwater,” says Eberhart. “One of the beauties of the Silva Cell system is that existing utilities to a great degree could stay in place. It definitely gave us the best solution.”