Interlocking Pavers - A Cost-Effective, Long-Term Solution in Cold Climates

When the city of North Bay, Ontario, explored the use of interlocking concrete pavers for its heavily trafficked downtown city center in the early 1980s, officials of this city of 54,000 wanted to know they’d be getting the most for their money. Not only did the resulting installation meet aesthetic and functional goals, it has since become a model of low-maintenance cost savings that has proved durable well beyond its projected lifespan of 20 years.

At the time of its completion in 1983, the $3 million, 150,000 sf (13,900 m²) Main Street project, which included roadway and sidewalks constructed on the full width of the road allowance, was hailed for its aesthetic contribution to a revitalized downtown business and retail district. When surveyed eight and 16 years later, the pavement was found to be performing exceptionally well under high traffic and extreme weather conditions, with little evidence of distress, despite minimal maintenance needed. In fact, after 12 years, a city official confirmed that there had been no maintenance at all. In addition, a 1999 life cycle cost analysis that compared the concrete paver installation with a local control section of hot-mix asphalt pavement found a difference of about $76,000/lane-km in maintenance costs favoring the concrete pavers.

Thirty-two years later, the installation is still performing, though finally ready for replacement, says Adam Lacombe, P. Eng, North Bay senior capital program engineer. The city is budgeting for a paver replacement to begin in 2017 or 2018. “Main Street has always been the centerpiece of the city, and the [pavers] set it off,” he says. “We are [considering] replacing them for their aesthetic quality and lifespan.”

Extreme Applications

The Main Street project was conceived at a time when the city of North Bay was planning to update its central business district with a more people-friendly scale and unified appearance. As part of the transformation, approximately 50 percent of the on-street parking was recommended for removal. In its place, designers envisioned wider sidewalks, boulevard areas and the addition of trees and planting areas, new benches, underground wiring and new streetlights.

Aiming to attract shoppers to a refreshed retail destination at a time when traditional Main Street businesses were losing business to shopping malls, North Bay’s Engineering and Public Works Departments gave interlocking concrete pavers first consideration in part for their potential to create an aesthetic identity for the district. But another major goal was to find a pavement that could handle an expected traffic volume of 8,000 vehicles per day (5 percent delivery trucks and buses), as well as snow removal and harsh weather conditions.

In North Bay, temperatures can range from −40 C in winter to 35 C in summer, and punishing freeze-thaw cycles occur throughout the winter months, with frost depths of up to 8 ft (2.4 m). The Main Street roadway would be subject to approximately 300 tons of salt annually, as well as the regular impact of the carbide steel blades used on snow-removing graders, slushers and plows.

At the time of the project’s conception, interlocking concrete pavers were already in use in high-load, harsh-weather projects around the world, and were just beginning to gain wider interest for heavy-use projects in North America. Just one year before the North Bay Main Street pavement was installed, 610,000 sf (56,700 m²) of interlocking concrete pavement was used in what is now called the Pier IX Terminal, in Newport News, VA. This facility handles ground storage of coal, so the pavers are subject to high loads from coal storage piles and abrasive loads from steel-tracked bulldozers. This provided an example of durability in an industrial setting.

North Bay officials had some experience with concrete pavers, which had successfully performed in an area around city hall for five winters under de-icing salts. But that area was not subject to vehicular traffic, so additional evidence was sought to prove the material and its installation could withstand projected traffic load and environmental conditions long-term.

A seminar that brought in experts from Australia, England and the Netherlands demonstrated to North Bay stakeholders how pavers had performed successfully under extreme loads and weather conditions in container ports, airports and roadways. Presenters offered compelling evidence that, when designed and executed correctly, the installation would withstand the rigors of a heavily trafficked Northern Ontario Main Street.

Best Practices Defined

The manufacturers, designers, engineers and installers involved in the Main Street installation set their sights on creating a state-of-the-art model showcase for what was recognized as a high-profile project. The pavers were manufactured to resist abrasion and freeze-thaw conditions, meet compressive strength and absorption standards, and were subject to a salt immersion test. Installation included a compacted subbase and base, edge restraints in the form of cast-in-place concrete curbs, concrete collars around utility structures such as manholes to offer a stationary restraint for the pavers, a herringbone pattern to provide the greatest degree of interlock (except in the crosswalks, which use a running bond pattern), and a slight crown in the roadway to allow for natural settling and drainage after construction. Sub-drains were utilized in some locations and surface water was designed to flow to catch basins and storm sewers.

During construction, installers performed regular density checks of the base with a nuclear density gauge to achieve the specified level of compaction that is critical to long-term performance. Nearing the end of installation, a plate compactor was used to force bedding sand into the joints and to facilitate the process of paver interlock, which in turn enables the transfer of vehicular load from paver to paver.

From today’s perspective, the North Bay Main Street project helped define best practices for interlocking concrete pavement manufacture and installation, some of which later became ASTM and CSA standards, including those for compressive strength, freeze-thaw durability and dimensional durability, and remain in use today.

Test of Durability

At eight years post-construction, an engineering consultancy performed a detailed condition survey and non-destructive deflection testing of the Main Street pavement. The survey found that about 4 percent of the approximately 57,000 sf of pavement surveyed had depressions concentrated in an area that had been subject to improper repair of the base when reinstalled after utility repairs. Another section that showed spalling resulted from incomplete joint filling and subsequently pavers losing interlock. Aside from this, the report concluded that the pavements provided “excellent performance…surface deformation occurs in less than 1.5 percent of the pavement areas surveyed,” and that the pavers were in “very good to excellent condition.”

Sixteen years after completion, in 1999, a geotechnical engineering consultant performed another condition survey that included a comparison with a local control section of asphalt pavement. It concluded that the interlocking concrete pavement showed little evidence of distress, with pavement condition indexes (PCI) for tested sections averaging 70 on a scale of 0 to 100 (with 100 showing no distress).

At 20 years, North Bay Public Works confirmed that the pavement was expected to be serviceable for another 15 to 20 years with only minimal maintenance anticipated.

A Cost-Effective Option

As part of the 1999 survey, a 40-year model was used for a life cycle cost analysis comparing the pavers and an asphalt street model that concluded rehabilitation of the pavers would be required at Year 21 in order to maintain a pavement PCI of 60. For the asphalt pavement, rehabilitation would correspond to years 18, 27 and 36 to maintain a PCI of 60.

At a 4 percent discount rate (corresponding to a secure investment of 6 percent and inflation of 2 percent), interlocking concrete pavements were shown to be more cost-effective than asphalt pavements. The study did not reflect costs to the public in downtime from routine maintenance and repairs. Interlocking concrete pavers can have a significant benefit in terms of reduction of these user delay costs because traffic can be restored very quickly after repair; also, less maintenance downtime is required over the pavement’s lifespan.

Since 1983, North Bay has continued using interlocking concrete pavers in public sidewalks, boulevards, its train station and lengthy promenades along its award-winning Lake Nipissing Waterfront Park. In 2010, it added a one-block section of pavers in a roadway that complements nearby Main Street and sets off a roadway island park. Likewise, cities across the United States and Canada have since chosen pavers for a variety of low- and high-impact projects, taking advantage of their endurance, aesthetic qualities and green attributes, more recently including permeable installations that aid in stormwater management.

The details of North Bay’s Main Street pavement rehabilitation are still to be determined as the city works on a new land use and urban design plan, says Mr. Lacombe. A rough estimate for replacing the pavement, including design and construction, is currently $2.4 million, he says.

North Bay faces the same decisions as hundreds of cities across North America: how to replace an aging downtown roadway in a way that’s economical in the short and long term, while taking into account aesthetic and environmental considerations, and the needs of stakeholders. The Main Street project offers strong evidence that interlocking concrete pavers are suitable for high-impact applications, and can be the most cost-effective pavement solution when considering total cost of ownership over the long term.

http://interlockdesign.org/Taking-the-Long-View

Stormwater Master Class Series at Forester University Expands

Jeffrey L. Bruce FASLA is now teaching Fundamentals of Green Infrastructure for the Post-Construction Stormwater BMPs Master Class Series at Forester University.

http://www.foresteruniversity.net/masterseries-postconstruction-Stormwater-BMPs.html

Daylighting Takes Off as Cities Expose Long-Buried Rivers

There's likely an underground stream in your city, but it may soon be seeing the light.

Uncovering buried streams has had huge impacts in places as diverse as Seattle, Washington, Kalamazoo, Michigan, and even Seoul, Korea—improving local water quality, providing habitat for fish and birds, and turning neglected parking lots and roads into public parks that boost neighbors' property values and can revitalize entire cities. And city planners everywhere are starting to take note.

In Yonkers, the fourth largest city in New York State, officials are a third done with a "daylighting" project—a term for the opening up of underground streams (see "11 Rivers Forced Underground"). In addition to exposing a waterway that had long been covered, the effort has already sparked plans for a new minor-league ballpark and new housing.

"I credit the city and the people who ... figured that having a nice river in a downtown was something that was, economically, really good," said Ann-Marie Mitroff, director of river programs for Groundwork Hudson Valley, an environmental justice nonprofit.

But why are all these streams covered at all? Flash back more than a hundred years. In many urban areas around the world, small streams were just getting in the way. You couldn't build on top of them, and the rapidly growing populations in many cities were throwing all their sewage into open water.

Often, engineers found that the simplest solution was to bury the streams, routing the water into pipes and paving over the top. In Yonkers, "the Army Corps of Engineers put a parking lot on top of it, which everybody thought was progress," Mitroff said. [Editor's note: A spokesperson for the U.S. Army Corps of Engineers says there are no records of the agency covering streams in Yonkers, and said the Corps would not have had jurisdiction to do so. They pointed to local authorities as most likely responsible; National Geographic has been unable to confirm that.]

In some cities, more than 70 percent of streams have been paved over. In many cases, city residents don't even know that there are buried waterways under their feet.

Now, new research and a desire to revitalize urban cores is leading to a host of daylighting projects. Uncovering buried streams has been proposed in San Francisco, Baltimore, and Detroit, as well as in smaller urban areas nationwide.

Uncovering streams can help reduce flooding. When it rains in a "natural" watershed, soil and plants absorb the water. When it rains onto a parking lot that drains into an underground pipe, the potential for flooding is much larger.

According to a new report from advocacy nonprofit American Rivers, released July 17, urbanization increases the likelihood of floods getting worse. One study found that paving over 25 percent of a watershed could turn a formerly rare severe flood into a twice-a-decade event. When more than 65 percent of a watershed is paved over, those so-called "hundred-year-floods" could hit every year.

Watch the Money Flow

Early daylighting projects, like Arcadia Creek in Kalamazoo, focused on the economic benefits of bringing streams back to the surface. Turning a parking lot into a 3/4-mile-long (1.2-kilometer-long) strip of Arcadia Creek in downtown Kalamazoo created a park that hosts five annual festivals and generates $12 million in annual tourism dollars.

But Arcadia Creek isn't really a creek. According to a report from the Virginia Tech Water Resources Research Center, the Arcadia Creek project and similar ones do "not resemble streams per se, but rather canals with surrounding parkland ... [the streams] are very controlled water channels [with] concrete-lined basins."

In Seoul, a $384 million project daylighted three miles (five kilometers) of stream that has most of its water pumped in from a river seven miles (11 kilometers) away. Both parks have been successful in boosting the economic value of the surrounding land and bringing locals a little closer to nature.

Digging up a stream isn't cheap. In Hutchinson, a town in rural Kansas, daylighting just three city blocks of Cow Creek cost more than $4 million, including relocating four buildings out of the new floodplain. But compared to the cost of unearthing, replacing, and reburying the city's aging pipes, building a new downtown park was an easy choice.

Not all daylighting projects need to be the centerpiece of an urban revitalization project. In Washington, D.C., the District Department of the Environment (DDOE) is undertaking small daylighting projects of a few hundred feet (around a hundred meters) in upper Northwest D.C., which is more suburban than urban, despite its location within the nation's capital.

Each project will create a small amenity for immediate neighbors, but they are mostly intended to mitigate local flooding and improve water quality. "Water in a pipe is not exposed to biological processes that break down pollution," said Steve Saari, watershed protection specialist with DDOE.

A recent EPA study found that streams exposed to sunlight are up to 23 times more efficient at processing nitrogen, which left unprocessed can cause dead zones where fish cannot survive.

Return of a "Living Stream"

In Yonkers, the uncovered stream is "a living stream," Mitroff says. The first reopened part of the stream (which opened in 2012) is already filled with fish and "fairly good-size" American eels, up to 18 inches (46 centimeters) long. "It's remarkable," Mitroff said.

In D.C., only months after daylighting a tributary to Rock Creek, "we've seen a lot more birds, and a lot more unusual birds," said Saari. And, he added, "we had frogs. It was incredible."

http://news.nationalgeographic.com/news/2013/07/130730-daylighting-exposing-underground-rivers-water-urban-renewal/

Reconsidering the Underworld of Urban Soils

by Laura Solano

Look down. If you are in a city or large town, below you is a vast network of hidden systems that support your life: pipes that carry natural gas, potable water, stormwater, sewage, and communications wires. These pipes rarely come to mind, but we agree that their operation is for the common good, that survival is not possible without them, and that armies of workers should keep them running. Surrounding those pipes are soils that are equally critical to our existence but to which we give much less attention. If we truly understood the delicacy of soil as a dynamic living system integral to the health of our towns and cities, our neighborhoods and families, we would be more cautious about how it is perceived, treated, and protected. Healthy soil performs important functions such as sequestering CO₂, mitigating stormwater runoff, supporting plant life, and sustaining the microbial populations that form the basis for all living things. So essential and complex are the conditions for soils in more developed areas that a new branch of science has arisen and is now being intensively pursued: the science of urban soils.

The Challenges of Urban Soils

Urban soils are are naturally-occurring soils that have been disturbed by development in a way that affects their functioning and properties. Urban soils are distinguished by a number of similar features: Their horizons (the natural vertical order of soils) have become jumbled by excavation. This makes urban soil horizons confoundingly diverse; one layer may be hospitable, but adjacent layers may not be, creating abrupt changes that can cause impermeable interfaces. Soil structure (the balance of solids and pores) has been crushed out of existence by mechanical compaction that chokes off water and air exchange. Organic matter (the source of plant nutrients) is low or missing from lack of replenishment, and this imbalances the soil biological community (bacteria, fungi, nematodes, arthropods, earthworms, insects, and more). Soil volumes that are important for plant health decrease because of interruptions from urban debris such as construction waste and rocks. Finally, the predominance of pavement separates soils from natural inputs such as nutrient-rich leaf litter, and this separation causes the nutrient cycling system to slow or shut down.

In the urban environment, soils are likely to be sealed off from the agents that build healthy soil—including wind, precipitation, ice, temperature, gravity, and mineralization—which frequently have been replaced by anthropogenic processes detrimental to soil functioning. Urban soils often become defined by human activities and land use histories at a particular location rather than by the continuum of geologic processes. This disrupted order makes urban soils particularly challenging to analyze, manage, and construct.

Urban Soils in the Service of Stormwater Management

Urban soils have the potential to be an important partner in stormwater management, use, and protection. The Natural Resources Conservation Service has recognized that soils with good infiltration and permeability can significantly reduce stormwater runoff rates and volumes that might otherwise overwhelm and impair the performance of the chain of water bodies that sustain our water supplies and the ecosystems that are necessary for healthy living [1]. Good infiltration reduces runoff by letting water soak into soils before it builds up to damaging volumes and velocities that would erode topsoil and carry both silts and pollutants to waterways. Permeability influences how quickly absorbed water drains through soil to useful depths for plants and recharge. Water that reaches root zones reduces irrigation needs. Some soil can filter toxic compounds or excess nutrients by holding them, degrading them, or otherwise making them unavailable. All of these benefits are feasible when soil has adequate pore space, which is only possible when soil’s natural physical texture and structure have been preserved or created.

Over-compaction of soils is one of the greatest deterrents to implementing best practices for stormwater management, because crushed particles minimize pore space and prevent water and air from moving through. In a study by the University of Florida, soil compaction from construction vehicles reduced infiltration by 70 to 90% [2].  This is perilously close to impermeable pavement.While people recognize that reducing pavement is the primary way to improve stormwater management, few see the same connection with soil. It is not enough to substitute pavement with plant beds if nothing has been done to prevent construction compaction. Without a soil management plan that includes practices for dealing with compaction before, during, and after development, urban soils will continue to become, plot by plot, a decommissioned resource in stormwater management.

 A Partnership between Urban Soils and Vegetation

The greatest positive effect of healthy urban soil is most evident in plants, the workhorses of the environment that clean the air, absorb CO₂, abate high temperatures, support wildlife, slow stormwater runoff, and keep erosion in check. In recent years, there has been resurgence in support for increasing the vegetation and tree cover in American cities. We are well aware of the positive ecological, social,[3]  and economic value of plants for individual properties, community open space, and urban regions [4]. Ecologically, a single large tree in the city is said to be ten to twenty times more beneficial to the environment than a single tree in the forest [5]. Yet the health of urban trees is declining at a rapid rate. A recent study by the U.S. Forest Service looked at twenty cities and found that they are losing tree canopy cover on average by 3% per year [6]. While this loss may seem small, over time the cumulative effects are severe. For example, Washington, D.C. lost 64% of its acreage-coverage from 1973 to 1999 at an average annual rate of 2.5% [7]. Still we continue to ignore the most basic need of trees: healthy soils. On most urban sites, fertile topsoil is absent, plant roots are restricted, air and water movement is suppressed, and nutrients cannot be exchanged. All this puts plants at an extreme disadvantage. The evidence of poor soil is all around, telegraphed by unhealthy plants. So if trees are to become “beautiful utilities” as urban tree expert Henry Arnold [8] suggests, then soil must also be treated in projects as an essential utility: analyzed, engineered, budgeted, scrutinized, and maintained.

Advocating for Soil

There are sound economic reasons to invest in good soil. As one of the core infrastructural materials in every urban landscape project, soil needs only to be tended more carefully to make it a viable component of stormwater management. Using soils to store and retain water as part of the stormwater management system can reduce costs for piping, drainage structures, runoff storage tanks, irrigation systems, and infrastructure maintenance and can provide more flexibility in design, since hard systems can add horizontal and vertical complexity that limits design options. Plants (especially street trees) with well-functioning soil are more able to start and sustain the nutrient cycling system without big infusions of maintenance after establishment and in maturity. When they do get maintenance, they are more likely to respond. Healthy soils beget trees that live longer and grow bigger, enabling them to cast more shade, and absorb more CO₂, and runoff. Even asphalt benefits from healthy trees, since shade improves its performance and durability [8]. Last, trees in good quality soil are far less prone to infection and pests, virtually eliminating the need for chemical treatments [9]. Investing in soil is critical for the long-term health of urban trees and by extension for the success of sustainable landscape projects and green infrastructure programs.

Why then do urban soils get so little attention when they are such a critical part of our environmental infrastructure and, ultimately, of human well-being? Some of the unawareness stems from societal and governmental ignorance. While keeping water and air usable is an unquestioned necessity, few people have the same association with city soils. For the most part, urban soil is considered mysterious, complex, and costly. Design professionals have an important role to play in dispelling unwarranted concerns and helping solve tangible problems: They should lead the way, project by project, educating their clients, agencies, and others about the need for healthy soil. Before that happens, designers must step up their own soil education. My interactions with colleagues suggest a dearth of understanding of basic soil science and the need for soil management in landscape projects. Often other landscape architects reach out for soil advice only when something has gone wrong. Designers do however have a thirst for this information as is shown by the increasing number of packed sessions in soil education at the annual meeting of the American Society of Landscape Architects (ASLA), the professions’ largest organization. Perhaps the neglect is also due to the fact that soil is not yet a hip topic; it has no visual presence. For many, design attention is reserved for visual effects; the hidden, infrastructural elements of landscape have long been considered the domain of engineers and scientists.

In my work as a landscape architect at Michael Van Valkenburgh Associates, soil discussions begin early, sometimes in the concept phase and always by schematic design. Soil is always an item on the design checklist. Just as all practitioners request surveys to locate utility lines, we request USDA soil tests to understand what we have to work with. Partnering with soil scientists, we have learned to interpret laboratory tests so we can ask the right questions and frame discussions. We keep up with developments in soil science (biology is the big topic now), often consult allied professionals, incorporate quality control practices into our specifications, and closely monitor sourcing, blending, and installing of soils during construction. We consider soil rigorously, as we do any other product or system in our projects.
I don’t mean to imply that assuring good soil is obvious or easy; it is neither, even for a firm that has been attempting it for twenty years. Every project brings unique soil challenges and clients with different agendas. The client may be unfamiliar with non-traditional stormwater approaches and therefore reluctant to consider soil-dependent systems. Brownfield properties often have contaminated soil or no useful soil at all. In other kinds of properties, existing soils could be reused if amended, but space may be too limited to manage soil-blending operations. Sometimes soil chemistry is limiting. For example: elevated pH from concrete or limestone rubble can interrupt nutrient exchange and narrow plant selection; high salinity in soil near tidal waters wreaks havoc on water uptake and cellular structure in plants. Local contractors often have no experience with installing designed soils. In my experience, construction managers show little tolerance for any aspect of landscape construction that is dynamic, an inherent characteristic of soil in particular and landscapes in general. Unless we have a repeat client, the process of educating, convincing, and making monetary tradeoffs to get good soil starts anew on every project. Sometimes we battle the sins of others’ projects in which someone tried but failed to improve soils. Projects with unsuccessful or difficult soil processes often produce rumors that the landscape architect specified unrealistic soils that cost too much and slowed the schedule, even if the problem was caused by the laxity of a member outside the design team.

Repositioning Soil as Infrastructure

How can we begin a campaign for good urban soil? We can start by talking with city hall, one of the biggest makers of landscapes and planters of trees, about the importance of soil. How many of the thousands of landscapes planted every year include soil improvement? Atlanta, Detroit, Denver, Los Angeles, and many other cities have tree-planting programs. Ambitious past and current mayors like Richard Daley and Michael Bloomberg launched campaigns to plant a million trees. Despite current commitments to increasing urban vegetation through tree planting, under current practices the mortality rate for young street trees is shockingly high: Some studies have found that over twenty-five percent of newly planted trees die within two years of installation [10,11], wasting already strained public funds and leaving behind a depressing reminder of failed nature. Wouldn’t it be more strategic to forgo planning one million trees in poor soil and instead plant 500,000 trees in good soil? [12]

To be stewards of urban soils, we need to ask pointed questions early in and throughout projects and insist on satisfactory answers that ensure positive long-term results for stormwater and planting. When zoning requires developers to add or replace trees, we need to ask for more than in-kind caliper inches and to require a soil management plan. When contractors install soil, they need to treat it like the valuable commodity it is or bear the cost of remediation. State and municipal specifications (which are used by contractors defensively instead of proactively) already define which dirt is suitable for backfill—why not extend this thinking to include requirements for the type, procurement, handling, and installation of planting soil? Landscape architects and anyone else who works with the landscape need to heed these too. Such guidelines should not be overly technical or onerous. Plant species should be matched to soil conditions, especially its pH and water supply. Trees should be planted at the right elevation to expose the root flare so soil doesn’t suffocate the tree. Adequate soil volume (800 to 1400 cubic feet per tree) and shared root space to encourage root spread should be provided [13]. Soils should be arranged to mimic the horizons in nature in which the top is rich in nutrients, the middle has the correct structure to encourage root growth, and the bottom is drainable. To resist compaction and maintain water and air exchange, soils higher in medium-to-coarse sands (rather than easily compactable fine sands and loam) should be used, and limits on density should then be set. Wet or frozen soils should not be moved or installed. To promote water and air exchange, rootball zones in tree pits should be exposed and at least half of the surface area of a plant bed should be left open, or a simple aeration system should be installed. Well-aged compost should be used to to provide 5% to 10% organics to the top layer of soils. And last, utilities should be placed at least three feet from trees.

There are more technical elements and specifications to consider, especially for sites with no soils, but as Stuart Shillaber the superintendent of horticulture at Boston’s Rose Fitzgerald Kennedy Greenway Conservancy advised me recently about introducing organic maintenance, “be happy when someone can implement 60% of the program. The rest will come when clients see results.”

The installation and upkeep of our existing “hard” utility systems requires substantial public and private investment. Creating well-functioning soils would not require large funds from the public since this work can be achieved project by project.  Upkeep of hard utilities is costly and disruptive; not so for soils that can be tended several times a year with substantially less trouble. The ASLA estimates that every year nearly 4.6 million acres are affected by public and private landscape projects [14]. Making headway on a quarter to third of that amount would start a revolution.

The Future of Urban Soils

From my vantage point, prospects for improving urban soils are good. In my thirty-year career as a landscape architect, there has never been a time of greater interest, research, and resources for managing urban soils and as many successfully constructed projects using urban soils. Advocacy for higher quality soil is rising nearly forty years after Dr. Phil Craul (professor emeritus at SUNY) and his colleagues started the field studies on urban soils that led to his 1992 publishing of the seminal Urban Soil in Landscape Design. Today, the USDA’s National Resources Conservation Service has substantial mapping, literature, and research on urban soils [15]. Ted Hartsig, a division chair of the Soil Science Society of America, tells me that the organization recently formed an urban soils division and committee whose focus is issues of urban soils including morphology and classification, the relationship of chemicals and nutrient quality, physics, biology, and structure, as well as the restoration and management of these soils. Urban soils studies are proliferating at public and private universities like Johns Hopkins and Kansas State.

Most critically, the public is starting to understand at the personal level of their gardens that the old adage “better to put a $5 tree in a $50 hole than to put a $50 tree in a $5 hole” is correct. Remember that until professionals and individuals teamed together to demand action, climate change was downplayed. Landscape architects and other professionals must play a part, whether through projects, lobbying our government, writing articles, lecturing, self-education, or speaking up in any propitious situation. We can be plausible leaders in the discussion to invest in another underworld utility, the first that is purely for the public good.

References

[1]  Soil Quality Information Sheet. Soil Quality Indicators: Infiltration”, Natural Resources Conservation Service, USDA, January 1998 http://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs143_019144.pdf

[2]  J.H. Gregory, M.D. Dukes, P.H. Jones, and G.L. Miller, “Effects of urban soil compaction on infiltration rate,” Journal of Soil and Water Conservation, Volume 61, Number 3. http://abe.ufl.edu/mdukes/pdf/stormwater/Gregor-et-%20al-JSWC-compaction-article.pdf

[3]  Geoffrey H. Donovan, David T. Butry, Yvonne L. Michael, ScD, Jeffrey P. Prestemon, Andrew M. Liebhold, Demetrios Gatziolis, Megan Y. Mao, American Journal of Preventive Medicine, “The Relationship Between Trees and Human Health: Evidence from the Spread of the Emerald Ash Borer,” Volume 44, Issue 2, pp. 139–45, http://www.ajpmonline.org/webfiles/images/journals/amepre/AMEPRE_3662-stamped_Jan_8.pdf

[4]  “Statistics on the Economic Value of Trees,” Conservation Montgomery, http://conservationmontgomery.org/resources2.html

[5]  “Study: Nations urban forests losing ground; New Orleans, Albuquerque, Houston losing Trees.” News Release, USDA Forest Service, February 23, 2012, http://www.fs.fed.us/news/2012/releases/02/urban-forests.shtml

[6]  Stephen C. Fehr, “Mayor Working To Keep It Green; Williams Pleads For More Trees,” Washington Post, November 17, 1999, http://caseytrees.org/wp-content/uploads/2012/02/02.01.1999-original-article-washingtonpost.pdf

[7]  Henry Arnold, “Sustainable Trees for Sustainable Cities,” Arnoldia, Volume 53, Number 3, 1993, http://arnoldia.arboretum.harvard.edu/pdf/articles/1993-53-3-sustainable-trees-for-sustainable-cities.pdf

[8]  E. Gregory McPherson and Jules Muchnick, “Effects of Street Tree Shade on Asphalt Concrete Pavement Performance,” Journal of Arboriculture, Volume 31, Number 6, November 2005, 303, http://www.fs.fed.us/psw/publications/mcpherson/psw_2005_mcpherson001_joa_1105.pdf

[9]  “Basics of Organic Maintenance”, UMass Extension, Center for Agriculture, http://www.extension.org/pages/62978/basics-of-organic-landscape-maintenance

[10]  “New Research Survey Suggests Urban Trees are On the Decline,” Public Radio International, March 16, 2012, http://www.pri.org/stories/science/environment/new-research-survey-suggests-urban-trees-are-on-the-decline-8967.html

[11]  Jacqueline W.T. Lu, Erika S. Svendsen,
Lindsay K. Campbell, Jennifer Greenfeld, Jessie Braden, Kristen L. King, and Nancy Falxa-Raymond, “Biological, Social, and Urban Design Factors Affecting Young Street Tree Mortality in New York City,” City and the Environment, Volume 3, Issue 1, 2010, http://digitalcommons.lmu.edu/cgi/viewcontent.cgi?article=1069&context=cate

[12]  “As City Plants Trees, Some Say a Million Are Too Many,” The New York Times, October 18, 2011, http://www.nytimes.com/2011/10/19/nyregion/new-york-planting-a-million-treestoo-many-some-say.html?pagewanted=all

[13]  James Urban, Up by Roots: Healthy Soils and Trees in the Built Environment, International Society of Arboriculture, 2008

[14]  “What is Landscape Architecture?” American Society for Landscape Architects, http://www.asla.org/nonmembers/LicPac99.htm

[15]  Soil Quality Information Sheets, Soil Quality Institute in cooperation with the National Soil Survey Center, NRCS, USDA; and the National Soil Tilth Laboratory, Agricultural Research Service, USDA, http://soils.usda.gov/sqi/publications/publications.html#utn

Suggested Reading

Timothy A. and Philip J. Craul, Soil Design Protocols for Landscape Architects and Contractors, Jon Wiley & Sons, 2006.

James Urban, Up by Roots: Healthy Soils and Trees in the Built Environment, International Society of Arboriculture, 2008

“Standards for Organic Land Care, Practices for the Design and Maintenance of Ecological Landscapes”, NOFA Organic Land Care Program publication, Northeast Organic Farmer’s Association, 2011. http://www.organiclandcare.net/sites/default/files/upload/standards2011.pdf

“Landscape Performance Series: Benefits Toolkit, Fast Facts Library, Scholarly Works”, Landscape Architecture Foundation, http://lafoundation.org/research/landscape-performance-series

http://landscapeurbanism.com/article/reconsidering-the-underworld-of-urban-soils/