This post is written by Katrina Marland and originally appeared on Loose Leaf, the blog of American Forests. 

American Forests has had a lot to say over the years about the relationship between forests and water. From protectingsourcewater to managing overflow in cities to advocating for forests’ integration into the Clean Water Act. And of course, we’ve been planting trees to restore watersheds for decades. Despite all this, the message about forests and water only really hit home for me when I learned about the water in New York City.

The Big Apple has more than eight million people living it, and all of them need water. How one city can provide clean drinking water for this many people boggles the mind — or at least, it sure boggled my mind. That is, until I found out that a lot of the work is done before the water even arrives in the city.

Good old NYC receives 90 percent of its water from the well-forested mountains that cover the rest of the state: the Catskills.New York City’s watershed spans the Catskill Mountains and the Hudson River Valley. This watershed includes two reservoirs, which together deliver roughly one billion gallons of water to New York City every day. But here’s the kicker: the water that comes from the reservoir in the Catskills is such high-quality water that it doesn’t need to be artificially filtered. The water that comes out of the faucet in an eighth-story apartment in the middle of the concrete jungle is the same water that flows through the remote forest upstate. That forest does such a good job of cleansing and purifying the water that there is no need for any additional filtration.

Think about the implications of that for a minute. Not only is it a concrete, quantifiable example of a benefit of forests that is often overlooked, but it also equates to a lot of money in the bank. The cost of constructing and maintaining a filtration plant that could process those one billion gallons every day would be truly incredible. To put it in perspective, the city is currently spending roughly two billion dollars to build a filtration plant to filter water that comes from the Croton Reservoir, which accounts for only 10 percent of the city’s total water use.

Forests take on a whole new value when you realize how much money they may be saving you. In 2007, the Environmental Protection Agency tested NYC’s Catskills water to make sure that it still met the requirements for unfiltered water, and it passed with flying colors. To continue taking advantage of the water-cleansing properties of their watershed, New York City designates funds for conservation in the Catskills. The cost is minimal, especially compared to the alternative, but the benefits are a healthy forest and a healthy watershed, with all the benefits provided by both. I call that a win-win.

Learn more about the role that forests play in your water and how you can help protect them by visiting American Forests’s Forests & Water page.

Image: mwanner

As Installation Coordinator, a big part of my job at DeepRoot is working with contractors to help make sure that they are comfortable installing the Silva Cell and to act as a technical resource when needed. Many contractors have questions about productivity during Silva Cell installations, which is what I want to talk about today.

Let me start by saying that any discussion of productivity and productivity rates is challenging because of the number of variables involved. Factors such as the length, width, depth (number of layers), access, working room, size of equipment, motivation of the workers, etc. will all effect the productivity rate that is ultimately achieved.

With that said, here is some general information that will help guide conversations about productivity when installing the Cells.

Assuming the excavation has already been done and the aggregate sub base prepared, a four man crew (3 laborers and 1 operator) should be able to complete an installation of 100 to 150 Silva Cell frames in an 8 hour day. “Complete” here means installing the frames and the geogrid, filling the frames with soil, backfilling around the outside and attaching the decks.

The two most time-consuming tasks during the installation process are excavating the Silva Cell area and then filling the frames with soil and backfilling around them. Laying out the frames, stacking the layers, attaching the geogrid and installing the decks takes very little time in comparison.

Here are two photos from of a project where the crew completed the installation of 90 frames in a day (10 frames x 3 layers x 3 trees):

*Surface area = approximately 9.3 sq meters x 3 = 27.9 sq meters.
*Volume = 9.3 sq meters x 1.219 meters (3 layers x 16 inches/layer) x 3 = 34.0 cu meters

Here is an example of a larger site and larger equipment, where the crew completed an average of 204 frames in a day (34 frames x 3 layers x 2 trees):

*Surface area = approximately 29.3 sq meters x 2 = 58.6 sq meters.
*Volume = 29.3 sq meters x 1.219 meters x 2 = 71.4 sq meters

(Calculation includes 1.5 inch/.0381 m space between frames and the 4 ft x 4 ft/1.22 m x1.22 m tree opening.)

As with any type of construction, there are too many factors to offer any type of guarantee for installation times, but hopefully these examples will give you some idea of what to expect on your projects. Please feel free to contact me (pat@deeproot.com) with any questions or to discuss the specifics of your project.

Last year, the Uptown Circle, in Normal, IL, was honored with the IL-ASLA President’s award. Now it’s been awarded an EPA “Smart Growth” award as well.

Rob Gray wrote about it last year:

Designed by Hoerr Schaudt Landscape Architects, the Uptown Normal Circle is an unusual roundabout in the heart of a new redevelopment district in Normal, IL. It was conceived to showcase Normal’s commitment to sustainability and creates a space where naturally-cleansed stormwater, public space, and transportation work in unison.  As the Circle calms traffic, it also provides a central green gathering space with seating, a water feature, shade, and an open plaza.

A major element of the project is sustainable stormwater management; capturing, storing, cleansing and recycling much of the stormwater in Uptown Normal.   Runoff is collected from several streets adjoining the Circle and is stored in a 75,000 gallon underground cistern. Water captured and retained in the cistern is then either used for irrigation of turf and plant material in the district or is introduced into the Circle.

Water collected in the cistern is pumped into a series of terraced filtration bogs where it is cleansed as it flows slowly through the plant material around the circle. The water is then pumped into an underground reservoir, treated by a UV filter and then circulated through a shallow stream-like water feature that entices interaction on a hot summer day. On its journey through the Circle, the water becomes a demonstration of sustainability in an urban environment.

Trees are a critical part of the redevelopment and we utilized Silva Cells throughout, both within the park space of the Circle and along several blocks of streetscape improvements.  We were looking for a solution that would provide the best growing conditions for the diverse collection of large caliper shade trees planned for the project.  Recognizing the importance of the ring of London Planetrees would play in the design of the Circle, the Silva Cells provided the ideal means to integrate trees into a plaza that primarily consists of paving.  The Silva Cell system also enhances the stormwater retention capacity of the area helping to alleviate burden on the regions network of streams and rivers.

The Uptown Circle has been embraced as a new symbol and focal point in the community. Its unique role as an example of high-performance infrastructure, integrating multiple civic elements such as roadways, pedestrian corridors, stormwater quantity and quality control and public space into a single project, has distinguished it from traditional forms of urban redevelopment.

Images: Hoerr Schaudt Landscape Architects

Man, those Torontonians! They continue to impress us with their aggressive green infrastructure policies. Back in January of 2010, Toronto became the first North American city to make installing green roofs on new commercial, institutional, and multifamily residential developments compulsory – now that requirements will apply to industrial developments as well. 

Like street trees, rain gardens, and other landscape features, green roofs are environmentally-friendly tools to help reduce urban heat island effect (thereby reducing energy demand), absorb significant amounts of stormwater on-site (avoiding sewer overload), and provide a pleasant habitat for local wildlife – as well as just adding a great deal of beauty to our urban spaces.

According to Toronto’s standards, small residential and commercial buildings (less than six stories, I believe) are exempt.  Beyond that, the larger the building, the larger the requisite green area. For the biggest structures, up to 60 percent of available roof space may require vegetation.

Industrial buildings have less strict requirements – only 10 percent of available roof space must be covered, unless, according to Kaid Benfield’s article about it, “the building uses ‘cool roofing materials’ for 100 percent of available roof space and has stormwater retention measures sufficient to capture 50 percent of annual rainfall (or the first five mm from each rainfall) on site.”

Buildings may request variances from Toronto’s City Council to have a smaller green roof than is mandated, but but to do so will cost. The collected fees, which are adjusted by building size, are then invested in incentives for further green roof development

Last fall, Green Roofs for Healthy Cities announced that Toronto’s green roof requirements had already yielded more than 1.2 million square feet (113,300 square meters) of planned new green spaces throughout the city. By their math, this will result in taking more than 435,000 cubic feet of stormwater offline and energy savings of over 1.5 million KWH each year.

Curious about what the wording for all of this looks like? Read Toronto’s municipal bylaw that includes standards for when a green roof is required and find out what elements are required in the design.

Image of Toronto City Hall’s green roof: Bricoleur Urbanism
Image of Toronto’s green roofs over time: GreenRoofs.org

Last week we attended a Silva Cell green roof installation at the Medical Mart and Convention Center in Cleveland, OH.

This project was designed by URS Corp. and installed by Independence Excavating.

There are two main areas of Silva Cells on the site. These pictures show the first area, which is part of a green space/festival space built over structure.

There will be trees in long planters at the borders of the space with intermittently placed concrete pads between for displays, etc.  The majority of those pads are supported by Silva Cells in order for the trees to share soil volume in the planters.

The second Silva Cell area is across the street to the south and is part of the green space/festival being constructed over the top of the convention center. There the Silva Cells will be used to provide soil volume to the street trees along the drives at on the east and west sides of the space.

Both phases of the installation are on structure.

All in all, about 70 trees will be planted on the site.

See more photos of the installation on our Facebook Page.

Today we have another reprinted post from Bert Cregg, an Associate Professor in the Department of Horticulture and Department of Forestry at Michigan State University. It originally appeared on his blog, The Garden Professors.

As usual, the beginning of spring is a busy time on the research side of my appointment.  This past week we began setting up for a major new project.  The goal of our newest study is to look at physiological traits of street trees that may enable them to better withstand future climate change.

If you think about it, trees that are planted today may experience future climates in their lifetimes that will be different than the climates under which they were selected.  So how do we ensure that trees that are planted today can withstand a potentially different environment in 50 or 75 years?  It’s a very complex question.  An easy response would be to plant species or seed sources that have evolved in warmer, southern locations.  The problem is climate change is predicted to occur gradually so southern trees moved northward today will be subject to increased frost and freeze damage in the interim.

Grad student Dana Ellison (L) and undergrad research aide Aniko Gaal (R) pot up shade tree liners for a new project.

Another approach, and the one we are investigating, is that trees that are best suited for the future may be those that have a high degree of phenotypic plasticity.  What is phenotypic plasticity?  Simply stated is the relative ability of a species or genotype to acclimate to changes in their environment.  In our case we are going to look at the photosynthetic response of a range of street tree cultivars in order to identify their optimum temperature for photosynthesis or Topt.  But we know from other studies that Topt can vary depending on the environment to which trees are acclimated.  So we will acclimate our trees to a range of temperatures in a greenhouse study and determine which species or cultivars are best able adjust their physiology to changing environmental conditions.  In addition to the greenhouse study we will out-plant trees from the same cultivars in a parallel field study with the Greening of Detroit.  Working with the Greening we will identify sites around Detroit with contrasting temperature regimes and plant trees at these locations.  We will follow up with a similar suite of measurements as our greenhouse trial.

Will one study tell us everything we need to know about selecting street trees for a changing climate?  Of course not.  But it provides some important base line information and insights on approaching the problem.  Trees in urban and community forests are already operating at the margins and subject to myriad of stresses.  The argument can be made that urban ecosystems are among those most at risk under climate change.  Trees are an important component of many climate change mitigation strategies but they must be able to survive and grow in order to contribute this function.

The study “Urban tree selection in a changing climate” is funded by Michigan State University Project GREEEN, with material and in-kind support from J. Frank Schmidt and Sons Nursery, Nursery Supplies, Inc., Renewed Earth, Inc., and the Greening of Detroit.

Top photo: Stuck in Customs
All other photos: The Garden Professors

Man. The day is finally here. The Silva Cell installation guidelines are now available on our YouTube channel.

This should be helpful for anyone looking for detailed Silva Cell installation instructions and examples. While we expect it to be of interest to landscape architects, architects, and engineers who design using the Silva Cell, it may also be valuable for owner’s representatives, QA/QC, and other people involved with the construction process.

The full video runs just a smidge over 13 minutes. If you’d rather watch it in sections, we have it broken out in to those as well.

Part 1: Overview of the Silva Cell system
Part 2: Preparing for the installation
Part 3: Preparing the excavation area
Part 4: Preparing the base aggregates
Part 5: Constructing the first layer
Part 6: Constructing the second layer
Part 7: Attaching the geogrid
Part 8: Loading the soil
Part 9: Backfilling the perimeter
Part 10: Adding the strongbacks
Part 11: Installing the decks
Part 12: Finishing the backfilling
Part 13: Adding the geotextile fabric
Part 14: Placing the aggregate base course
Part 15: Installing the curbs and pavement
Part 16: Installing root barrier

We hope to have a version of the video available in Spanish later this year.

A quick disclaimer: this video is meant to be a general overview of the installation process. Individual designs may include elements or adaptations that  are not covered in the video.  Please contact us (info@deeproot.com or 415-781-9700) to discuss the specifics of your project further.

This post originally appeared in Next American City.

In February, the U.S. Forest Service published a report indicating that cities around the country are losing around 4 million trees per year. Of the 20 cities included in the study, 17 showed significant losses of canopy cover, and 16 showed significant increases in impervious hardscape (or paved surfaces that don’t absorb water). At the same time, cities like Los Angeles, New York, Salt Lake City and Philadelphia continue to announce “Million Tree” planting initiatives as part of citywide green infrastructure efforts.

But are these initiatives likely to result in long-term success for urban trees? I’m not optimistic. That’s because we can’t expect to increase canopy cover, environmental utility or tree mortality rates simply by increasing the number of trees we plant — we have to change how we plant them.

Trees are a huge asset to their communities, yet we frequently fail to plant them in viable conditions where they can grow to maturity. Why are mature trees important? As trees grow, they provider greater and greater economic and environmental value, becoming increasingly effective at lowering temperatures, reducing energy costs, enhancing property values and calming traffic. At mature sizes, trees begin to function as meaningful green infrastructure.

For example, a study by U.S. Forest Service researchers shows that a tree with a 30-inch trunk circumference delivers 70 times the air quality benefits of a tree with a 3-inch trunk circumference. Urban trees are a part of almost every development, yet mature urban trees are rare, and might be the most underutilized resource for leveraging maximum value and utility from public spaces.

There can be many reasons why urban trees fail to grow to useful sizes, but the most critical is that they generally don’t have access to sufficient amounts of soil, resulting in a short death and replacement cycle. We remove them — at ongoing expense — before they ever grow big enough to make much environmental or economic contribution. According to the Maryland Department of Natural Resources, the average lifespan of a tree in a downtown area is less than 10 years. At a time when we are facing more serious environmental threats than ever before, leveraging the many benefits that trees offer is critical.

Planting trees in conditions that will support long-term growth is the first way in which we need to revise our assumptions about trees as green infrastructure. For trees to live to 60, 70 or 80 years old they need adequate amounts of high-quality soil — around 1,000 cubic feet per tree. Our estimates indicate that trees planted in 1,000 cubic feet of soil pay back their costs after around 20 years. And those trees should be around and contributing substantial economic value for many decades beyond.

Properly planted trees also play an important role in stormwater infrastructure. This is arguably where they have the greatest value. The soil trees grow in alone is capable of managing rainfall events of up to two inches, which is greater than the average storm event in many places. As trees grow bigger and put out fuller canopies, their capacity to manage stormwater via interception (the amount of rainfall temporarily held on tree leaves and stem surfaces) increases, which can provide significant additional stormwater benefits beyond storage in the soil.

I’m not trying to pick on Million Tree initiatives. Garnering public support and involvement in tree planting is an important part of the long-term success of the urban forest. My point is simply that we need to pay attention not just to quantity of trees, but to quality andperformance. That must start with ensuring that they have access to adequate soil volumes, even in paved areas like sidewalks, parking lots and plazas.

Some cities across North America are beginning to address the problem of in adequate planting conditions by setting soil volume minimums for street trees. Toronto, Ontario has the most ambitious program: Their Green Standard calls for street trees in shared soil volumes to receive a minimum of 15 cubic meters (529 cubic feet) per tree, and for single trees to receive a minimum of 30 cubic meters (1,059 cubic feet) per tree. The West Virginia Department of Environmental Protection, Athens-Clark County in Georgia, Markham, Ontario and the Denver Parks Department are some of the other municipalities that are setting soil volume minimums to ensure the long-term viability of their trees.

We make massive investments in “gray” urban infrastructure features, like pipes and light poles, with the expectation that they will perform as efficiently and effectively as possible for decades — even though they lose value as soon as they go online. Trees work in the opposite way and require us to plan a little differently, yet the potential payback is enormous. Designing conditions for trees to grow and thrive in urban areas will significantly leverage their value and effectiveness to the community at large, and we all stand to benefit.

This picture is of the Venice Island Recreation Center, in the Manayunk neighborhood of Philadelphia, PA.  The island sits between the Manayunk Canal and the Schuylkill River and between the Lock and Cotton Street. And in about three months, Silva Cells will be installed here. It will be the first usage of this product by the Philadephia Water Department.

Once completed, the Venice Island Recreation Center will actually sit atop a large water storage facility, which is designed to hold the run off from the 100 year storm event from a multiblock area. The Silva Cells will hold water from the rec center building and the parking lot before it enters the tank, thereby capturing the 90% rain event for the smaller catchment area.

You can read more about this project on Naked Philly.

A combined sewer overflow (CSO) – the “the discharge of wastewater and stormwater from a combined sewer system directly into a river, stream, lake or ocean” – sounds bad enough. But have you ever seen one?

This 2010 footage of the Gowanus Canal, in Brooklyn, is pretty sobering. Can there be any question that we need to urgently prioritize design solutions that manage stormwater where it falls?