From the ground up: Sustainable sites start with healthy soils

Published on
08 Dec 2021
Danielle Pieranunzi
Article Headers 2021 (p2)

Photos courtesy of SITES Certified US Land Port of Entry in Columbus, New Mexico

Soil is the living skin of our planet: the foundation of all terrestrial life, regulator of our atmosphere, ultimate recycler of our waste and source of our water, food and materials. But as we’ve populated this planet and shaped it to our needs, we have often forgotten how essential soil is for our very survival. 

SITES strategies to improve soil health

Because soil formation is a slow process, it is critical to protect soil that is already healthy and restore where it has been degraded. For the SITES v2 Rating System, this translates into several design standards and strategies that redefine the development process to ensure we create a regenerative, healthy and resilient future.

  • Conduct a site assessment. Where and when soil health is compromised isn’t always readily apparent.That’s why SITES projects conduct a thorough site assessment (per Prerequisite 2.2) before design and construction begin with team members that have soil expertise. Project teams can then understand existing soil conditions early on and use this to inform design. At this stage, it is also essential to understand the reference soil conditions to inform future restoration efforts needed for the soil management plan. (A reference soil is a healthy native soil found on site. If none exist on a site, SITES asks projects to use undisturbed native soils within the site’s region that support appropriate native vegetation similar to those intended for the project site.)
  • Conservation is critical. That’s why SITES requires projects to protect areas that are healthy and already providing critical and essential functions like with farmland soils, floodplains and wildlife habitat. That also means avoiding the disturbance or removal of other healthy soil found on-site (per Prerequisite 4.1, Credit 4.4), as well as importing soil from offsite greenfields or healthy farmland. 
  • Establish protected areas during construction. To ensure soil protection before and during construction of any SITES project, a “Vegetation and Soils Protection Zone” must be designated and then communicated to the project team and contractors (per Prerequisite 2.3). Specific strategies that minimize disturbance from construction activities and treatment plans for restoring soils are required in SITES. 
  • Test your soil. To ensure degraded soil has been restored properly, SITES projects test their soil once it’s restored to meet certain criteria that include soil organic matter, compaction, infiltration rates, biological function and chemical characteristics (per Prerequisite 7.3 and Credit 7.4). Properly restoring soils with mature, stable compost is one of the best tools for building resilience in built landscapes. By increasing water storage, plant-rooting depth, temperature attenuation, plant vigor and hardiness are enhanced.  
  • Integrate soil health in your site maintenance plan. To ensure long-term site sustainability, the ongoing activities that protect the integrity of this essential ecological system must be outlined and communicated to site managers in a site maintenance plan (per Prerequisite 8.1).

Fortifying soils at the Columbus Land Port of Entry in New Mexico

“We wanted to be very specific to the site and its constraints when it came to our approach to the native soil and selecting plant material,” says Aaron Zahm, Principal at MRWM Landscape Architects and landscape architect for the SITES Certified Columbus Land Port of Entry project in New Mexico. “There is a tendency to overly amend the soils or assume you need to, like applying lots of organic material or chemicals to change the PH or reduce the salinity. You might get a soils test and the lab recommendation is to leach salt from the soil using lots of water and then to apply thousands of pounds of chemical fertilizers or soil conditioners. In reality, what we found was that the organic content, PH, and the salt we were dealing with was not uncommon to the native Chihuahuan desert grasslands, so we knew that if we could be very careful about our plant selections, we could actually work with the soils on site.” 

US Land Port of Entry's soil plans

Healthy soils are invaluable for supporting robust vegetation and providing a multitude of ecosystem services, such as filtering pollutants, sequestering carbon, reducing runoff, protecting water supply, controlling erosion and supporting wildlife. The foundation of many green infrastructure and water conservation strategies starts with healthy soils.

The careful attention and value of soil and vegetation for the site design that was embodied by the Columbus Land Port of Entry team resulted in numerous benefits such as:

  • 12.5 acres of restored grassland
  • 97% reduction in water consumption for irrigation. This is a savings of 3,045,970 gallons per month, during the peak establishment period.
  • 2.5 million gallons of stormwater directed to landscapes annually (helping with the reduction in irrigation use)
  • Cost saving from not depending on so many amendments for the soil (estimated to be over $150,000 in initial construction costs)
  • Protected carbon sinks and reduction in carbon emissions from less material being transported to the site and less conventional maintenance over time
  • Reduced maintenance costs from choosing a native restoration versus a typical ornamental landscape  

Combating climate change through soils

Protecting any healthy soil onsite also helps to keep carbon in the ground. While SITES Credit 4.4 rewards projects for conserving any healthy soil (and stored carbon) on site, later SITES Prerequisite 7.3 and Credit 7.4 focus on properly restoring soils where they have been degraded without the use of sphagnum peat

Materials Credit 5.10: Support sustainability in plant production incentivizes project teams purchase plants from businesses that use peat-free growing media. This is critical because while peatlands cover less than 3% of the world’s surface, they contain approximately 42% of all soil carbon worldwide and exceed the carbon stored in all other vegetation types, including the world’s forests. They grow at a mere sixteenth of an inch a year; peat mining removes layers that take centuries to develop. A lack of awareness of the benefits of peatlands means that they have been severely overexploited and damaged. About 15% of the world’s peatlands have been drained and this has released huge amounts of greenhouse gases.

To further enhance the awareness and understanding of the impact site and landscape design have on carbon (both emissions and sequestration), GBCI released a new SITES pilot credit this year, Assess and Improve Site Carbon Performance to not only assess but also quantify carbon emissions and carbon sequestration capacity, and then make improvements to their project’s impact on carbon based on this new understanding.

US Land Port of Entry's xeric shrublands

Thoughtful soil management will also save money. By limiting site-grading activity, SITES-certified projects will reduce costs for construction machinery and transport of imported soils and conserve resources like water over the life of the project. A healthier site produces a healthier community too, whether you are maintenance personnel for a corporate campus, or a family visiting a local park. Because healthy soils support healthy plant growth, there is less need for pesticides, fertilizers and the fossil fuel-based “mow and blow'' type approach to maintenance. We all benefit from this. If managed sustainably, this often-overlooked yet vital and beneficial part of a landscape will also foster resilience in communities that face uncertain climate-related extreme weather, whether drought, flood, disease or northward-shifting growing zones. As Franklin D. Roosevelt once said, “A nation that destroys its soil, destroys itself.”

Learn more about SITES approach to soil in the SITES Rating System, and see if SITES certification could be right for your project.