A few years ago I wrote an article about how LEED v4 addressed designing for trees, soils, and stormwater (green infrastructure). Two big things have changed since then, so a follow-up explaining what’s new in this sustainable building certification system is in order:
- Project registration for LEED v2009 was extended by two years – by extension, the transition to LEED v4 has been delayed by the same amount of time.
- LEED purchased SITES (a landscape certification system) and in time may be incorporating the relevant parts of SITES into what were once LEED’s weakest sections: site (landscape) and water.
What does the acquisition of the SITES program mean? How will it be blended with LEED? What are the key elements of the SITES rating system? And, most critically, how will this affect the treatment of trees, soils, and stormwater?
Is LEED the leader?
I wrote in 2013 that LEED was the most widespread and successful third-party sustainable rating system for buildings on earth, and could be for all built spaces, both indoors and out, if it also incorporated a less well known system: SITES (Sustainable Sites Initiative). By adding SITES into its certification program LEED further solidifies its leadership position, with no serious contenders on the horizon. If you want to rank sustainability of the built environment, LEED is still the franchise to invest your time and money in (this is my honest opinion; I have never worked for or received any consideration from LEED).
My earlier pieced touched only briefly on LEED 2009, because at that time it was about to expire. Now, however, that deadline has been extended because LEED users felt the schedule for transitioning to the newer version was too aggressive (it takes a long time to become proficient with each new version of LEED). The delay in transitioning from LEED 2009 to LEED v4 is unfortunate from a green infrastructure standpoint: because of the extension, thousands of projects will become LEED certified that are very deficient in regards to soil and trees.
William McDonough, an early proponent and leader of sustainable buildings, has often talked about how the practice of making buildings sustainable is largely a process of making the building process “less bad,” i.e. less wasteful of building materials, less of an energy hog, and so on. All of this is because of what buildings cannot do: be regenerative.
Not so for the landscape. Soil and trees both have regenerative qualities, including their ability to sequester carbon, evapotranspire stormwater, capture pollution, and more. I’m paraphrasing McDonough, but trees process atmospheric carbon dioxide by generating two major “waste” products – oxygen and wood. No toxic waste needs to be cleaned or removed as a result of this process. No building, no matter how clever our sustainable efforts are, can be regenerative. Trees, soils, and stormwater are the essence of regeneration.
What does SITES do for soils and trees that LEED doesn’t?
From a greenfield development perspective, SITES is exceptionally rigorous. It far exceeds anything in LEED v4 and LEED v2009, and that’s a triumph. It is also a performance-based system rather than a prescriptive one, which is a huge sustainable plus.
SITES’s most urgent general weakness is in addressing site and water sustainability for “Urban In-Fill,” a project type that is now starting to dominate land development. Professional landscape architects and civil engineers were the two professions most involved during a period of development from around 1970 to 2007, when large portions of North America were being turned into suburban and exurban housing. I have lived and practiced in two large Midwestern urban areas, Chicagoland and MSP (Minneapolis/St. Paul), in which most professional work for civil engineers and landscape architects revolved around suburbanization. It’s the curse of us baby boomer land development professionals, as in when you’re a hammer, everything looks like a nail.
Cities surrounded by flat land in the Midwest and the Sunbelt were particularly hard hit by this urban sprawl. For 25 years, from 1983 to 2007, the amount of developed land in the United States increased by 56 percent. This 30+ long year period of out-of-control greenfield development is the prime driver that led to the creation of SITES.
How SITES developed – and works
SITES is a rating system for sustainable landscape design that started in 2009 and was a cooperative effort, and jointly owned, by the National Botanic Garden of DC, the Ladybird Johnson Wildflower Center in Austin, TX, and contains the membership practice expertise of the 15,000+ members of the American Society of Landscape Architects (ASLA).
Unlike LEED, SITES addresses the outside of the building envelope. The peer reviewed SITES system, after years of mining the literature and ASLA’s reservoir of experience, used a case study approach to road test the Version 1.0 credit system. Over 100 projects were accepted during this testing period; once completed, 46 sites received the SITES certification imprimatur. More importantly, the certification system had a chance to work out the kinks in monitoring, metrics, measuring, and crediting.
The SITES certification system now contains 10 discrete sections in which there are 18 prerequisites and 200 total points available to achieve certification. Like LEED, there are four project certification levels:
- Basic: 70-84 points (out of 200 possible points)
- Silver: 85-99 points (out of 200 possible points)
- Gold: 100-134 points (out of 200 possible points)
- Platinum: 135+ points (out of 200 possible points)
The 18 prerequisites are spread throughout seven sections required for all four certification levels. Each section also contains credit points which, unlike the prerequisites, as optional. These are the SITES sections that pertain most directly to green infrastructure:
- Sections 1 and 2 (Site Context and Pre-Design Assessment + Planning) are for information gathering, analysis and pre-design (up to 16 points available).
- Section 3, Site Design – Water, contains the areas of most relevance to soils, trees and water (up to 23 points available)
- Section 4 is Site Design – Soil + Vegetation (up to 40 points available)
- Section 7 is Construction (up to 17 points available)
SITES is a strong rating system, though I believe we can do even better. Here is an overview of the sections as they pertain to green infrastructure, along with my comments. (Other prerequisites and/or points are available in Sections 5, 6, 8, and 9 as well, but I won’t be examining those in detail).
Section 1: Site Context
SITES’s greenfield bias is apparent in the first four foundational prerequisites, all of which are specific to greenfield development: limit farmland development, protect floodplain functions, conserve aquatic ecosystems, and conserve habitat for threatened and endangered species. While these activities might be found on a piece of urban in-fill, it’s highly unlikely that all four would be present.
To be fair there are also optional credit points for redeveloping degraded sites (1.5) and locating projects within developed areas (1.6). C1.5 is primarily concerned with remediating brownfields and contaminated sites, which is a big plus, but has been embedded in both LEED and SITES for years. Many landscape projects are somewhere between greenfields and brownfields; It would be nice if there was points available for that level of disturbance, for example “urban compacted soils rehabilitation.”
Section 2: Pre-Design Assessment + Planning and Section 3: Site Design – Water
In Sections 2 (Pre-Design Assessment + Planning) and 3 (Site Design – Water), greenfield development is well covered for stormwater, but urban in-fill is (again) largely missed, as there is no mention of an existing stormwater piping system.
Section 4: Site Design – Soil + Vegetation
Section 4: Site Design – Soil + Vegetation got me very excited because the first prerequisite (4.1) is “Create and communicate a soil management plan” – this is an excellent first step on any project, and is equally applicable to both greenfield and urban in-fill development. Eight of the next ten items are clearly aimed at greenfields, however.
The greenfield bias shows up particularly in credit 4.4, which awards points for conserving healthy soils, but only in concert with existing vegetation. The exception to greenfields is the recognition of building impacts by vegetation in credit 4.9 (reduce urban heat island effects) and credit 4.10 (use vegetation to minimize building energy use), which can be a central part of urban in-fill development. If it were up to me, I would add another prerequisite to the existing three about specifying appropriate soil types and amounts based on what vegetation will be planted and on a stormwater management plan (if any).
Section 5: Site Design – Materials Selection
Credit 5.4 (reuse salvaged materials and plans) directly addresses both greenfield and urban in-fill development by awarding points for salvaging existing materials and plants. However, it falls far short by excluding recycled soils. Soil is typically the largest single material on any site that can be recycled and yet it is completely excluded. With the previous healthy soils bias in credit 4.4 (conserve healthy soils and appropriate vegetation), awarding points for soil recycling as per Section 1 “urban compacted soils rehabilitation” would be a huge benefit to urban in-fill sites.
Section 6: Site Design – Human Health + Well Being
Two points are awarded for both credit 6.4 (support mental restoration) and credit 6.6 (support social connection), but they cannot be for the same outdoor space. This is not called out, but points could be obtained with heavy duty tree rehabilitation in the root zone (again, a resource often found on urban in-fill sites).
The acknowledgement to provide unobstructed views from 50 percent of common spaces inside regularly occupied buildings is a real plus for tree groupings. The very last bullet of credit 6.4 mentions, among other landscape features, “a grove of trees…for a multi-sensory aesthetic experience.” This seems extremely watered down based on what we know about large on tree benefits. Based on Ulrich’s (healing) and Sullivan and Kuo’s (crime reduction) milestone research, other places in the target list are hospitals, prisons, and public housing. These ideas are equally applicable to credit 6.6.
Section 7: Construction
There are three prerequisites for this section: 7.1 (communicate and verify sustainable construction practices), 7.2 (control and retain construction pollutants) and 7.3 (restore soils disturbed during construction). 7.3 in particular is excellent and a long time coming.
Unfortunately, credit 7.4 – restore soils disturbed by previous development — is optional. This is yet another greenfield bias because on a urban in-fill site all the soils would be disturbed. If these soils are not rehabilitated, using soil and trees for stormwater infiltration will likely fail. To balance out this bias against urban in-fill development, I recommend that this credit change to become a prerequisite. Finally, credit 7.6 (divert reusable vegetation, rocks, and soil from disposal) are just the kinds of resources that can rehabilitate damaged soils. Hooray for credit 7.6.
Sections 8: Operations + Maintenance
Prerequisite 8.1 of this section, “Plan for sustainable site maintenance,” is a remarkable check-list for operations and maintenance activities. It includes a matrix of topics that is extremely helpful, however the section of soil stewardship does not address adequately the long term maintenance challenges of urban soils and their constant deterioration. There are three items in particular that I’d like to see addressed in a future version of this table:
- target a minimum Soil Organic Matter threshold (3 percent) be maintained;
- promote soil decompaction by maintaining an infiltration rate of 1” to 4” per hour (Kent et al);
- ban the use of dry chloride deicers on vegetation.
Section 9: Education and Section 10: Innovation
Both of these sections are entirely optional, but to increase site sustainability understanding of soils, trees, and stormwater with the general public – and to increase the body of data by monitoring and creating – case studies are very welcome. I hope people will go the extra mile and share the great work they are doing so that we can all learn from one another’s experiences.
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Green Business Certification Inc. (formerly U.S. Green Building Council, or USGBC), the owners of the LEED certification system, purchased SITES in June 2015. As a result of this, the landscape and site portion, which was once the weakest part of LEED’s rating system, is now closer to par with the rigor of the other LEED sections. In the last analysis, I believe this is ultimately the best home for SITES.
SITES was driven by a pre-Great Recession, unsustainable greenfield development model, however today’s urban in-fill model is very different – and has much different sustainable site challenges. I plan to write one more article that will go a bit more in depth about the components and consequences of a certification system conceived of and driven by this very different development paradigm.
L. Peter MacDonagh, FASLA, is director of science and design from The Kestrel Design Group.