Milwaukee Explores Using Basements for Stormwater Management

We’d like to pass on this approach that the City of Milwaukee is exploring for management of stormwater. Let us know what you think!

image credit:

image credit:


Read More

Minnesota Develops New Option For Property Owners, Municipalities And Others To Save Thousands Of Dollars By Installing Trees For Stormwater Management

Our very own Nathalie Shanstrom and Peter MacDonagh were quoted in today’s article about work on the Minnesota Stormwater Manual. Check out the article here:

Minnesota Develops New Option For Property Owners, Municipalities And Others To Save Thousands Of Dollars By Installing Trees For Stormwater Management

First-Of-Its-Kind Stormwater Crediting System Allows Communities And Businesses To Quantify Potential Of Trees To Manage Stormwater


The state of Minnesota has just developed a first-of-its kind formula and credit system that is transforming the way communities think about trees and stormwater management – and can potentially help them save thousands of dollars by investing in trees rather than pipes. The Minnesota Pollution Control Agency created the credit system as part of a new chapter on trees in their stormwater manual, which also provides recommendations on how to ensure that trees thrive and provide the maximum ecological benefits for planners, developers, landscape architects, and builders.


“To our knowledge, Minnesota is one of the first states, if not the first, to add a chapter on trees to its manual, as well as add analysis on the stormwater benefits of tree and soil systems,” said Nathalie Shanstrom, a landscape architect with the Kestrel Design Group who led the efforts to develop the credit system. “While trees have always provided stormwater benefits, they are just recently starting to be recognized by regulators as viable stormwater control measures. Cities, states and homeowners are taking notice.”


The federal Clean Water Act imposes requirements on stormwater discharges from specific municipal, construction and industrial activities. Minnesota is helping communities use trees and other green infrastructure to help address these requirements while mitigating the high cost of installing only pipes.


“The state encourages Low Impact Development (LID) practices where they are appropriate,” stated Mike Trojan of the Minnesota Pollution Control Agency. “Trees are potentially an important LID practice, and we want to ensure that the trees provide the maximum level of stormwater benefits.” The new credit system is part of Minnesota’s Minimal Impact Design Standards (MIDS), which focuses on treating rain where it falls to minimize negative impacts from stormwater runoff and to preserve natural resources. The credit is based on a formula that establishes criteria and methods to measure the benefits of evapotranspiration, which is the combination of water evaporating from the soil and transpiration from the plants growing in the soil.


An additional focus of the Minnesota stormwater manual is the importance of planting trees properly with adequate soil volumes, even in urban areas. The manual recommends soil requirements of two cubic feet of soil for a square foot of canopy area – the minimum for a healthy tree.


Tree size is crucial for maximizing stormwater benefits. For trees that are planted and maintained correctly and provided with adequate soil volume, the state is therefore giving credits based on the projected mature canopy size. If a tree is planted with less soil than it needs, the credit is reduced.


“Trees are the oldest form of green infrastructure in cities, but the urban forest is now broken,” said Peter Macdonagh, of Kestrel Design Group. “Planting trees in appropriate quantities of good soil and using stormwater and its nutrients to irrigate is beneficial to the urban forest and reduces city taxes by tens of millions of dollars. Minnesota’s visionary rule incentivizing correct tree-planting to manage urban stormwater will clean our lakes, rivers and oceans to be safely swimmable and fishable.”


Cities like Minneapolis, which do not have the space for open planters due to concrete and pavement, have already begun to invest in innovative solutions to attain the greatest stormwater credit possible. Through the use of products like the Silva Cell, which creates an underground framework that provides soil access to support long-term tree growth, the city is planting achieving the proper soil volume.


“States as diverse as Washington, Texas and Minnesota are looking for smart solutions that help them address stormwater management, and the Silva Cell system is the perfect tool,” stated Graham Ray, CEO of DeepRoot. “Depending on the size and design of the system, thousands of gallons of runoff can be prevented from entering, overwhelming or polluting sewers, creeks and adjacent watersheds. As more urban centers realize that they can save millions through the use of trees, we anticipate more people will turn to solutions like the Silva Cell.”


The new approach that Minnesota is taking is also leading to economic, ecological and community benefits to local residents. For example, trees lead to lower vacancy rates in business developments and have a number of aesthetic, energy, health and environmental benefits. Tress can help reduce asthma rates, reduce crime, and can serve as “nature’s air conditioners” in the hot summer.


As states look to alternative solutions to manage stormwater effectively, Minnesota and its new credit system is showing what can be done through simple formulas and technology that help incentivize sustainable, tree-filled communities.


To learn more about the new Minnesota stormwater credit, visit:


To learn more about the Silva Cell, please visit:


Read More

Project Update: 17th Street Residence Hall

I took advantage of this beautiful Friday morning to get out and take photos of one of our more recent landscape installations. The 17th Street Residence Hall at the University of Minnesota, Twin Cities campus, was wrapped up last year, and we’re nearing the end of the warranty period. Luckily, most of the plant material seems to have survived our long, cold, snow-filled winter and came out unscathed. I hope to get back out to the site at various seasons for more photos. It was difficult to get a good picture, but the Kentucky Coffeetrees look especially good. We were lucky to get some great plant stock at the time of installation.






Read More

Where in the World is Peter MacDonagh?

Peter-Amdam-1Those are big shoes I’m trying to fill. It’s very windy in Holland, but these clogs helped keep my feet on the ground, and these clogs are safety rated also! I had a great trip to look at Urban Trees & Greenroofs in Amsterdam, Malmo & Stockholm. I was honored that Joris Voeten biked with me around Amsterdam showing me lots of Amsterdam SBSS (Sand Based Structural Soil) projects. He also took me to this amazing little village of Dutch houses, windmills, barns, etc. collected from Holland. It’s like Disney World, but authentic in every way. Later, Tobias & Jonaton showed me a whole array of different green roofs in Malmo; then it was back to Urban Trees in Stockholm with Sophia, Orjan & Bjorn, here’s an inadequate but grateful thank you to them all. I learned that when have almost no land that isn’t under water and it’s all sand (Holland) or when you have lots of land, but it seems to be all rock, people can be extremely creative & inventive. My trip & my hosts instructed & inspired me in many ways, and I will start writing a blog in the near future to tell you about it. All the best, Peter

Read More

Stormwater and Silva Cell Webinar

Join Kestrel and DeepRoot at their upcoming webinar:

Webinar: techniques for directing water into silva cells
Tuesday, june 17th 2014, 12:00 – 1:00 PM EDT (9:00 – 10:00 am pdt)

Join us for a webinar with L. Peter MacDonagh, FASLA and Marcy Bean of Kestrel Design Group to learn about techniques for directing stormwater into Silva Cells.

On-site stormwater management and mimicking pre-development hydrology are becoming increasingly important design imperatives at every level. Trees and soils in suspended pavements are part of the toolkit for implementing meaningful stormwater control measures.

This webinar will discuss some of the most common techniques for directing stormwater into Silva Cells, including catch basins, curb cuts, and pervious pavement. Each technique will be examined using real-life project examples, with a discussion about why the solution was chosen for the site in question. We will walk through the logic behind the design, including project goals, pre-treatment, water distribution, and maintenance.


Title: Techniques for Directing Stormwater into Silva Cells
Date: Tuesday, June 17th, 2014
Time: 12:00 to 1:00 PM EDT (9:00 to 10:00 AM PDT)

We hope you can join us to learn expert techniques for directing stormwater into Silva Cells – Please register for the webinar here!

Read More

New data: “Sidewalk work blamed for toppling 3,000 Minneapolis trees last summer”

Image by David Joles, Star Tribune

Image by David Joles, Star Tribune

An interesting article was posted today on the Star Tribune website regarding the loss of large existing trees in last years wind storms. I am honestly surprised by the correlation of sidewalk work to the loss of these trees. In my opinion, it emphasizes the importance of planning for ultimate tree growth at the time of planting. Check out the full article here:



Read More