Sustainable Sites Initiative (SITES)

SITES Aims to Transform the Marketplace

12/12/201708/09/2019Jared GreenLeave a comment

ASLA 2017 Professional Communications Honor Award. Ecology as the Inspiration for a Presidential Library Park. Black Locust bridge. Michael Van Valkenburgh Associates / MVVA Inc

With the General Service Administration (GSA) and now the state of Rhode Island adopting the use of the Sustainable SITES Initiative™ (SITES®) certification system for landscape projects, SITES is gaining momentum. The system now has the potential to transform the marketplace for landscape products as well, explained Hunter Beckham, FASLA, a landscape architect; Meg Calkins, ASLA, a professor of landscape architecture at Ball State University; and April Phillips, FASLA, principal of April Phillips Design Works, in a session organized by ASLA professional practice manager Linette Straus, ASLA, at the 2017 Greenbuild in Boston.

Given SITES v2, which covers landscapes, and LEED v4, which covers all types of buildings, now have a number of synergies designers and developers can take advantage of, the potential market impact of SITES is even greater, Beckham said.

Calkins argued that it’s critically important landscape architects and designers leverage SITES to reduce the harvesting of Amazonian hardwoods for seating, decks, and boardwalks. “Some 18 percent of the Amazon has been cut down in the past 20 years.” With SITES, “we can transform the market away from tropical hardwoods.” SITES incentivizes this transformation with its prerequisites that “eliminate the use of wood from threatened tree species.”

For example, Ipe, a rare hardwood that appears once every 7-30 acres and is a signature species in the Amazonian rainforest, has often been used in landscapes because of its durability. But SITES — which refers to plants on the Convention on International Trade in Endangered Species (CITES)’s list of those threatened with extinction and the International Union for Conservation of Nature (IUCN) “red list of threatened species” — prevents the use of this endangered tree species in SITES-certified landscapes.

One big problem with the current approach, Calkins explained, is the “IUCN list is dreadfully behind.” Many tree species were last assessed more than a decade ago, so it allows many woods that are no longer plentiful, like Cumaru.

Another issue: In the Pará state of Brazil, some 28 percent of hardwoods are harvested illegally. Even some Forest Stewardship Council (FSC)-certified woods’ documentation is forged, with “shady chains of custody.” And while the Lacey Act is designed to prevent American companies from purchasing illegally-harvested rare Amazonian hardwoods, “fraud still happens.”

Instead of trying to find the few sustainably-harvested rainforest hardwoods, Calkins called for using alternatives like fused bamboo lumber, which is rapidly renewable and outperforms Ipe in durability; American Black Locust lumber, a hardwood native to the Ozarks and Appalachian regions and can be harvested in one-third the time of Ipe; thermally-modified woods, which are heated so they are twice as hard as the original wood and are disease resistant; polymerized woods, which has been developed in the European Union; and acetylated woods.

Furthermore, “landscape architects need to see environmental product declarations and quantifiable data” for all the products they are considering specifying. The architecture field is “way ahead” of the landscape architecture field in this regard of measuring and verifying the life cycle of products, as there are already a number of independent 3rd party product verification systems.

For Calkins, who researches the sustainability of landscape products, just finding basic information on wood products for landscapes is a challenge. “Corporate sustainability reports are a source of information, as are marketing brochures.” But, again, she is looking for independent 3rd party verification of any sustainability claims, and those don’t seem to exist for landscape products.

To shift the marketplace, landscape architects need to “ask more questions of product manufacturers, demand they disclose information and be transparent, and use environmental product declarations when specifying.”

According to landscape architect April Phillips, who has designed and built SITES-certified projects, the key is to track the sourcing of all materials from the get-go. In a “living roof native landscape” she created for 38 Dolores in San Francisco, she used 44 percent recycled materials and 60 percent regional ones.

38 Dolores / April Phillips Design Works

And for a new, 1,500-acre landscape on the site of a former airport in Alameda, California, Phillips is reusing found logs as benches.

Phillips also made the case for environmental product declarations, claiming that too often the only ones she can find are from products made in the Netherlands or New Zealand. And importing these products to the U.S. only adds to projects’ carbon emissions and is discouraged in SITES.

First SITES v2 Certified Landscapes Create Real Impact

10/11/201608/09/2019Jared Green1 Comment

University of Texas at El Paso / Ten Eyck Landscape Architects

Certifying your landscape project with the Sustainable SITES Initiative™ (SITES®)* can seem like an expensive, onerous process. So why bother? For Jamie Statter, vice president at the U.S. Green Building Council (USGBC), SITES gives landscape architects the “opportunity to do it right” and have an impact in the fight against climate change. In a session at GreenBuild in Los Angeles, she and two SITES consultants working with landscape architects on the first SITES v2 certified projects explained why it’s worth the extra effort.

In the face of sprawl, which is helping to speed climate change, “we must better value land as a resource. Sprawl is not about buildings; it’s about the landscape,” argued Statter. In too many places, sprawl happens because “land and water resources are undervalued.” With SITES, she said, “we can value the elements of the landscape that provide benefits that haven’t been monetized.” Through incorporating an ecosystem services-based approach, land owners can save crucial natural resources, reduce carbon emissions, and even make money.

Under SITES, landscape architects and designers can create broader impact through a range of projects: playgrounds, parks, university campuses, water reclamation projects, transportation systems, military facilities, and others. The site just must be a minimum of 2,000 square feet and must be new construction or a major renovation. The rating system tops out at 200 points, but it only takes 135 to reach platinum. SITES enables many kinds of approaches that fit local climates.

With the recent launch of SITES Approved Professional (AP), landscape architects now have “the chance to get ahead and further differentiate themselves,” she added.

The First SITES v2 Certified Project: The University of Texas at El Paso (UTEP)

Heather Venhaus, an environmental designer and author of Designing the Sustainable Site: Integrated Design Strategies for Small-Scale Sites and Residential Landscapes, was a consultant on the campus redesign project led by Christine Ten Eyck, FASLA, at Ten Eyck Landscape Architects, which was the first SITES v2 certified project, achieving a Silver rating. As Venhaus explained, UTEP is among the top rated campuses for upward mobility, meaning many of its students are the first among their families to attend university, so this project is also about social equity.

For the university’s centennial celebration, they revamped their 11-acre, greyfield campus covered in parking lots, spending some $14 million to transform it into a landscape that not only reflects the beauty of the native Chihuahuan desert ecosystem, but also rebuilds the ancient arroyos (rivers) that were once covered over by parking lots. Due to all that asphalt, the campus had major flooding problems. After those arroyos were restored, the water collected and infiltrated through the campus, managing water from up to a 95th percentile storm event. Any excess now flows out to the Rio Grande River instead of inundating the campus.

University of Texas at El Paso arroyos / Ten Eyck Landscape Architects

Before, the campus was filled with parking lots; now, it has outdoor seating for 1,800. “Spaces for mental respite went up 64 percent.” At night, many of these social spaces have gas fire pits, so students can hold events outside under the starry desert sky. “The campus now helps students’ cognitive abilities, creating spaces for healing nature.”

The transformation led to a 61 percent reduction in water use, with a 60 percent increase in vegetation, and a 98 percent increase in the native plant palette. Some 90 percent of demolition materials were diverted from the landfill and recycled on site. Venhaus said, “let no one tell you it’s hard to recycle asphalt. It’s the easiest thing to do.”

According to Venhaus, they lost points with SITES because they weren’t able to incorporate much recycled local materials. “We just couldn’t get recycled content, because the local market in El Paso didn’t have it.”

But the process was ultimately worth it, and the costs were relatively low. She said it’s possible to “use SITES and stay within budget if you start with the rating system from the beginning, using the pre-design assessment. You may have spend more on materials and documentation, but it’s typically less than 3 percent of the overall budget. About 1-3 percent.”

In an email, Ten Eyck wrote: “We are glad that we mentioned going after the certification at the beginning of the project to Diana Natalicio, the president of UTEP. She was all for it and gave us the back up for pursuing the certification, so we were able to incorporate the SITES strategies from the beginning of the design process. We learned that it can be difficult in remote areas, such as El Paso, to meet all of the criteria, because it is so far away from many manufacturers. The campus is thrilled to have received the certification, and the project is helping to convey to the El Paso region and beyond the importance of connecting people with each other and the beauty of their unique desert regions, away from cars. Campuses of the southwest do not have to copy British or ivy league approaches. Instead, we can celebrate the beauty of the people and the places of the southwest in our own special way.”

The Second SITES v2 Certified Project: Chicago Navy Pier

Bryan Astheimer, an architect and sustainability consultant at Re:Vision Architecture, worked with James Corner Field Operations to achieve SITES Gold certification for the transformation of the Chicago Navy Pier. For its bicentennial the Chicago Navy Pier put out an international design competition to reimagine the pier landscape, which Corner’s firm won.

The pier is the only one of the five Chicago architect and planner David Burnham envisioned as part of the 1919 comprehensive plan for Chicago to actually have been built. For decades it was used by the Navy, and then, in 1995 it was revamped as a “festival pier,” with a convention center, children’s museum, Shakespeare theater, restaurants, and amusement park. For decades, it has been the “number-one tourist destination in the Midwest,” Astheimer said. But the city found that the pier had begun to look “tired, not contemporary.” For many Chicagoans, it’s really a place only for tourists.

The first phase of the pierscape project, some 9 acres, redesigned the entry — the Polk Brothers Park and Headhouse Plaza — and the south dock, the long spine that connects the various rooms of the pier. Field Operations more fully integrated the entry plaza into existing transit systems, adding bike racks, bike share stations.

Chicago Navy Pier entry plaza / Sahar Coston-Hardy

The spine itself is a marvel of landscape engineering. Before, stormwater would simply run right off into Lake Michigan. Now, expansive tree tanks cut right into the pier with giant saws are large enough so they can store any excess water that falls on the pier. “Water is stored in the tanks where it’s used to irrigate the landscape. Any excess is filtered and then discharged.”

The number-one cost item on the project were the thousands and thousands of herringbone-patterned pavers needed to cover the pier. “We ended up custom specifying a paver with UniLock, but they couldn’t meet the SITES specification for 40 percent recycled content. They ended up creating a paver with 30 percent copper slag. It’s now on their website as part of their eco product line.” What began as a limitation ultimately resulted in market transformation.

Astheimer said “SITES makes you think through the site before you begin design. It forces you to use a quantifiable framework that creates learning opportunities” for all the designers and contractors involved. All the challenges that came out of this new process “were all opportunities for learning. Challenges create growth and ultimately value.” He believes that “SITES will drive the industry to become more sustainable and transparent.”

Sarah Weidner Astheimer, ASLA, principal, James Corner Field Operations, wrote in: “We are excited to celebrate the gold SITES certification of Navy Pier’s South Dock, the first phase in its complete renovation. SITES informed much of our design process, from access and circulation studies to plant and material specifications. It was an important tool that kept our client, our contractor, and design team accountable to a high standard of best practices and resulted in an unprecedented project—the transformation of Chicago’s Navy Pier into an authentic and green destination reflective of the city’s identity.”

*SITES was developed through a collaborative, interdisciplinary effort of the American Society of Landscape Architects (ASLA), the Lady Bird Johnson Wildflower Center at the University of Texas at Austin, and the United States Botanic Garden.

Landscape Architects and Their Clients Tackle SITES

11/26/201308/08/2019Jared Green1 Comment

We often hear from landscape architects about the cutting-edge sustainable design practices they are bringing to their latest Sustainable Sites Initiative™ (SITES®)-certified works, but we rarely hear from their clients. In a session at the ASLA 2013 Annual Meeting in Boston organized by Liz Guthrie, ASLA, professional practice manager at ASLA, landscape architects and their clients together discussed their motivation to become certified Sustainable Sites Initiative (SITES) projects, the challenges involved in working with this new 200-point rating system, and the lessons learned.

Why a Sustainable Landscape?

For Richard Piacentini, Phipps Conservatory and Botanical Gardens, the goal was to apply “systems-thinking” to their new Center for Sustainable Landscapes, which received the first four-star rating from SITES (see image above). “We wanted to know how we could truly integrate the building and landscape.”

He said too many buildings are “completely isolated nature.” This is a real problem because humans now spend about 80 percent of their lives in buildings of some kind. With the new center designed by landscape architecture firm Andropogon Associates, “nature is now not that far away.”

In the Bronx, Hunts Point Landing, a two-star SITES-certified landscape developed by the New York City Economic Development Corporation (NYCEDC) and designed by Mathews Nielsen Landscape Architects, shows how a “dead-end” in an isolated and unhealthy neighborhood can be turned into a park, said Kate Van Tassel, NYCEDC. The park is meant to ameliorate some of the health problems in the community, which has some of the highest rates of asthma and obesity in New York City.

The new Hunts Point Landing took shape on the site of an old coal gasification plant. Van Tassel said this little bit of “green space amid industry is very important.” To boost neighborhood health, NYDEC wanted a sustainable park. Old local materials were re-used within the park. Stones from a nearby bridge taken down were turned into blocks to sit on. The waterfront park helped “transform the shoreline into a recreation area.”

In the case of Taylor Residence in Chester, Pennsylvania, Margot Taylor, ASLA, is both the client and landscape architect. Taylor wanted to create a public demonstration project for sustainable landscape best practices on her own property. Her property includes wood systems and meadows. Ecological systems were re-established, with a focus made on soil and plant health. The landscape, which used to be a farm, now “directs, holds, absorbs, and cleans water.” She now has hundreds of people, including lots of school groups, touring the landscape each year.

One of Taylor’s goals in the move to a sustainable residential landscape was to reduce annual maintenance. She wants to get maintenance down to 55 hours a year. She has also “completely gotten mowing out of the system.”

Representing both himself and his client, Hunter Beckham, ASLA, SWT Design, described the design of the Novus International campus in St. Charles, Missouri. He said a “huge number of stakeholders” were involved in creating a sustainable campus, which was designed to yield many benefits for both employees and the environment. There’s a productive, edible landscape: a vegetable garden with bee-friendly plants. There are two bee blocks that provide home to seven different local species. In the first year, the landscape yielded 65 pounds of honey.

This vegetated garden terrace is accessible via a walking loop that circles the entire campus. The loop enables both employees and visitors to take a break from the office and get out in nature. Within the landscape, an old concrete-lined water detention pit was turned into a natural water habitat that manages stormwater and attracts a wide range of wildlife, including snakes.

What Were the Challenges?

For Jose Alminana, FASLA, a principal at Andropogon and one of the guiding forces behind SITES, the benefits far outweighed the challenges. He said achieving 4-stars for the Phipps’ Center for Sustainable Landscapes was no small feat, but perhaps made possible by the fact that “we started with no site.” The design team then had “complete control over the materials used,” which helped them improve site performance and earn points under SITES.

Still, “procuring the sand-based soils was a challenge, given the firms involved in fracking are very interested in applying the same soils to sites where they are extracting gas.” Separately, he added that it was “hard to change the plant palette to accommodate the new soil pH.”

For Signe Nielsen, FASLA, SITES seemed to be an exercise in frustration. She said there were three categories of SITES credits that deeply-urban brownfield sites like Hunts Point Landing “couldn’t take advantage of,” so the project could only get two stars.

She said she couldn’t preserve existing soils and vegetation because “they were highly contaminated.” There was “no structure to adaptively reuse,” so points couldn’t be gotten there either. Lastly, there were no “cultural resources to reuse or enhance.”

She added that working with public authorities, in effect, means “limited opportunities for integrated site design teams,” as many local governments don’t incentivize such groups.

More broadly, she thought that achieving many of the credits related to “recycled content materials will be challenging given the landscape industry has very few competitive vendors in this field.”

Urban public projects may have a challenge earning maintenance points as well, as the landscape architecture firms creating these projects often have “no control over future maintenance.” A firm could create a detail maintenance manual for a park, but then that’s it.

Taylor said working with a historic farm was a challenge in itself. The native vegetation had been stripped and topsoil eroded or compacted. The solution was to “rebuild healthy soil and native plant communities appropriate for different micro-climates.” SITES, she said, “didn’t want to give credits for the landscape’s past use as pastureland.”

She certainly ended up getting credits, though, for the 27 tons of barn stone she cut up and re-purposed on site by hand. “I lost about 15 pounds shifting all that stone out of the dirt.” Still, she thinks she needs to find a “smarter way to manage materials that were unearthed.”

What Lessons Were Learned?

Alminana believes that “integrated design is really the key” to achieving a return on investment for your clients and site performance. “SITES really puts an emphasis on this.” He said, unfortunately, this approach is still not “happening among a majority of the profession or in the public sector.”

Directing himself to those who complain they haven’t earned enough points for their projects using SITES, he said “if you are only focused on points, you are missing the point.”

Nielsen believes SITES can have a potent impact, given “metrics are crucial” and SITES really forces landscape architects to collect data and measure themselves against benchmarks. She said putting all that time into collecting metrics was worth the effort because it helps “clients understand the value of our work.” Landscape architects can measure how well they’ve “reduced noise, saved water, and reused materials.” Beckham reiterated how valuable SITES is as a “framework for accountability.”

Taylor learned that it’s important to “integrate a long-term land management perspective from the beginning,” something that SITES promotes.

The landscape architects all hoped that governments — both local and national — will get moving on incorporating SITES guidelines into their request for proposals (RFPs), which can also help push the landscape materials industry to provide more sustainable options. It will be a back-and-forth process to make SITES more mainstream: landscape architects, and their clients, must push for change among providers of landscape materials, but the market must also provide opportunities to enable that change.

Image credits: (1) Phipps’ Center for Sustainable Landscapes / Denmarsh Photography, (2) Hunts Point Landing / Mathews Nielsen Landscape Architecture, (3) Taylor Residence / Mark Gormel, (4) Novus International / SWT Design

SITES Certifies First Four-star Landscape

11/26/201302/18/2014The Dirt ContributorLeave a comment

The Sustainable Sites Initiative™ (SITES™) announced three new projects have achieved certification under the nation’s most comprehensive rating system for sustainable landscapes.

The newly certified projects are the Phipps’ Center for Sustainable Landscapes in Pittsburgh, which is the first SITES pilot project to have received the maximum four stars; Washington Canal Park in Washington, D.C., which received three stars; and Shoemaker Green, a university green space in Philadelphia that received two stars.

The SITES program is a collaboration of the American Society of Landscape Architects (ASLA), the Lady Bird Johnson Wildflower Center of The University of Texas at Austin, and the United States Botanic Garden. The SITES program was created to fill a critical need for development guidelines and recognition of sustainable landscapes based on their planning, design, construction and intended maintenance. This voluntary, national rating system and set of performance benchmarks can be applied to projects on sites with or without buildings.

The new projects join 23 others across the country that have achieved certification since June 2010 as SITES pilot projects. These diverse projects represent landscapes of various sizes, locations, types, and costs.

“We are very pleased to announce three new certified projects – particularly the first four-star rating,” said SITES Program Director Danielle Pieranunzi, who is at the Wildflower Center. “Each project has achieved a great deal by demonstrating innovative applications of sustainable land design and development practices while meeting the SITES 2009 criteria.”

As with the other pilot projects at universities, corporate headquarters and other landscapes that have previously achieved this recognition, the newly certified projects applied the SITES Guidelines and Performance Benchmarks 2009 and met the requirements for pilot certification. The guidelines and rating system were created by dozens of the country’s leading sustainability experts, scientists and design professionals.

The three newly certified projects incorporate diverse sustainable features:

Phipps’ Center for Sustainable Landscapes, Four Stars, Andropogon Associates, Pittsburgh, Pa (see image above). The Center for Sustainable Landscapes (CSL) at Phipps Conservatory and Botanical Gardens was designed to be the first project in the world to simultaneously achieve LEED Platinum, SITES four-star certification, and The Living Building Challenge (still pending). Built on a previously paved city maintenance yard and documented brownfield, the nearly three-acre site supports a new 24,350-square-foot education, research, and administrative building; manages all sanitary waste and a ten-year storm event on site using a range of green infrastructure strategies; has successfully reintroduced 150 native plant species; and is designed to be net-zero for energy and water. The CSL is open to the public and its building and landscape performance is being extensively researched and monitored to inform the design and construction of similar projects that restore ecosystem services, generate their own energy, and clean and re-use their own waste water.

Washington Canal Park, Three Stars, OLIN, Washington, D.C. One of the first parks built as part of the District of Columbia’s Anacostia Waterfront Initiative, Canal Park is a model of sustainability, establishing itself as a social gathering place and an economic catalyst. Located on three acres of a former parking lot for district school buses, the three-block long park is sited along the historic former Washington Canal system, and is a centerpiece for approximately 10,000 office workers and about 2,000 new mixed market-rate and affordable housing units. Canal Park’s focal point, a linear rain garden, functions as an integrated stormwater system that is estimated to save the District of Columbia 1.5 million gallons of potable water per year. The park also features electric car charging stations and a neighborhood-scale system for capturing treating, and reusing rainwater. Numerous opportunities are provided for residents and workers to enjoy the park, including an ice rink, a café, pavilions and space for concerts, movies, and farmers’ markets.

Shoemaker Green, Two Stars, Andropogon Associates, Philadelphia, Pa. As part of the University of Pennsylvania’s “Penn Connects” campus master plan, this deteriorating site with underused tennis courts was redesigned as a passive open space of lawns, tree-lined walkways, and sitting areas. The green space is both a destination and a pedestrian route from the core of campus to the historic buildings surrounding it. The site can be adapted for multiple events and activities at a wide range of scales, from secluded areas for eating lunch to staging areas for the Penn Relays and graduation ceremonies. Through the innovative use of various sustainable strategies and technologies, Shoemaker Green has also been optimized to capture and control stormwater from the site and surrounding rooftops, provide viable native plant and animal habitats, minimize transportation of materials to and from the site, and serve as a starting point for the development of a sustainable maintenance strategy for the university at large.

The 2009 SITES rating system for the pilot projects includes 15 prerequisites and 51 additional, flexible credits with assigned numbers of points that total 250. The credits address activities such as soil restoration, use of recycled materials and land maintenance approaches. Projects can achieve ratings of one through four stars by amassing 40, 50, 60 or 80 percent of the 250 points.

Based on the experiences of many of the pilot projects, a refined set of guidelines and rating system, SITES v2, is finalized and incorporates added recommendations from technical experts. This enhanced version of the 2009 SITES rating system is ready to be published for distribution and use by the general public.

Image credits: (1) Phipps’ Center for Sustainable Landscapes / Denmarsh Photography, (2) Washington Canal Park / OLIN, Sahar Coston-Hardy, (3) Shoemaker Green / Barrett Doherty

Designing with Soils

11/16/201308/08/2019Jared Green6 Comments

“Growing plants is the goal,” said James Urban, FASLA, Urban Trees + Soils, at the 2013 ASLA Annual Meeting in Boston. To grow healthy plants, one needs healthy soils, and landscape architects who understand soils and know how to call a soil scientist. In a wide-ranging talk, Urban and his co-presenter, soil scientist Norm Hummel, discussed how landscape architects can design with new soils the right way, particularly in challenging, damaged urban landscapes.

Whether natural or man-mixed, soils have physical, environmental, and chemical properties. These are all important to the health of a growing medium. Physical properties include organic matter, water, drainage, and aeration. Environmental characteristics include light and temperature. Chemical elements include the pH balance, and the presence (or not) of phosphorous, nitrogen, and potassium, which are all critical elements for plants.

To determine what kind of soil is needed for a project, Urban said goals and requirements are needed early on in the design process. Questions that need to be asked: “What type of trees and plants are you trying to grow? How big do you want these plants to get?” As an example, depending on the requirements, an oak can grow to 25 feet and last 50 years, or grow to its full extent and live hundreds of years. Landscape architects have think through these things in terms of soil early on.

It’s also important to know how a site is being used. A landscape may have lawn, but is that walked on a few times a year or thousands of times? Urban said the National Mall’s turf gets a quarter of a million visitors per day. That space gets 3,000 events a year. Use will determine what kind of irrigation and soils are needed.

Urban said there are eight critical properties of soils, which soil biologists can test to determine if soils meet specifications. They include structure, texture, density, nutrients, pH, organic matter, and density, which are all “inter-connected.”

More often than not, Urban said trees and plants don’t do well because of the physical properties of soils rather than the chemical. If something goes wrong — a tree is stressed, shows early fall color, or even dies — landscape architects may be planting the wrong trees and plants for the soil types.

Some details on soil’s physical properties: The structure of soils has to do with how well-glued together the soil particles are. Particles are attracted to other particles — and organic matter glues them together. Clay soil has a strong structure due to the stickiness of the soil. Silt soil has a weaker structure, while sand has no structure at all. Sandy soils are useful in areas that need to drain.

Urban added that man-made mixed soils are very different from natural soils. Mixed soils include soils that have been broken apart and put back together.

Soils are also made up of spaces or voids where water can flow. Ideal forest soils have a void space of about 50 percent, while urban compacted soils are around 20-30 percent. With the Sustainable Sites Initiative™ (SITES®), Urban said more landscape architects will need to measure soil structure.

Soil texture is also important to examine. Clay, silt, and sand all have different surface areas given the unique sizes of the particles. Fine sand is .24mm, while silt is 2.4mm, and clay, nearly 24mm. Just within the family of sand, there are huge differences as well, with fine sand having properties distinct from coarse grains.

Hummel, who said he has examined over 100,000 soil samples in his career, said organic matter is a major contributor to soil health. Organic matter can be amended with either peats or composts.

He said many peats are actually not sustainable and shouldn’t be used to augment the organic matter in damaged soils. Peat farming can strip an area of nutrients, creating environmental damage. However, he made an exception for sphagum peat, which is more expensive, but a renewable resource. For Hummel, sphagum peat is “superior to compost, which breaks down rapidly.”

But compost is most often added to soils to boost the amount of organic matter. Compost is often used with disturbed urban soils that have suffered from erosion and compaction. Compost types include yard waste (grass, wood chips), bio-solids (treated municipal sewage), animal manure, and mixed waste. Some regional compost specialties include pine bark and rice hulls. Hummel added that soils have a “disease suppressive capacity.” Still, he cautioned against the practice of using 90 percent compost and 10 percent soil, saying that a “tree planted in that will simply fall over or die.”

Hummel also delved into the chemical properties of soils – and whether it’s possible to chemically amend damaged soils. He concluded that altering the PH balance of existing site soils is “unrealistic.” What’s better is to focus on the availability of nitrogen, potassium, and phosphorous in the soil.

While sending soil samples to a lab will yield data on all these properties, these properties can also be requested in soil specifications. Hummel said landscape architects can even specify things like permeability in soils.

Urban concluded that it’s best to reuse dirt where possible, but sometimes grading and compaction have “killed the soils.” To understand the problems and solve them, landscape architects can use web soil surveys, study soil maps, take their own samples, examine them, and send them to the lab. “Landscape architects need to learn how to do this.”

To learn how to go on to the next step and fix soils, check out Urban’s book, Up by Roots.

Image credit: Sugar Beach, Toronto, by Claude Cormier / Deeproot