Site and Water Guidelines

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S.3 Soil Management

Maintain the permeable structure of the soil in order to optimize water infiltration/filtration capabilities and maintain the biological functions of the soil in order to optimize plant health and species richness.

Required Performance Criteria

  1. Create Soil Management and Erosion Control Plans to protect the soil profile of the site during and after construction.
  2. The bulk density of all unpaved pervious surfaces intended for seeding and planting shall have the following maximum bulk densities. Soils in these areas that exceed the stated bulk densities shall be decompacted to 18 inches prior to planting or seeding by air spading, ripping, adding organic matter (see S.3 F), or other decompaction method.
    • Clay and Silt: less than 1.25 g/cm3.
    • Loam: Less than 1.35 g/cm3
    • Sand: Less than 1.55 g/cm3
  3. Limit Soil Disturbance
    1. Limit soil disturbance (defined as grading, compacting, piling, tilling, scraping, storing, and removal of soil) to 40 feet beyond the building perimeter, 15 feet beyond primary roadway curbs, main utility branch trenches, pervious areas and stormwater management features, and 5 feet beyond walkways.
    2. Soil disturbance shall be no closer than 5 feet from tree driplines and/or the perimeter of site areas/features identified for protection. Trees shall be protected as individuals or as groups (canopies < 10' apart) with tree protection fence located 5’ beyond the drip line, prior to site activities.
  4. Maintain, establish, or enhance a 75-foot vegetated buffer for delineated wetland boundaries.
  5. Do not sell or export any top soil from project site. Stockpile and protect existing site topsoil or import topsoil for a respread of 12" in all proposed planting and seeding areas.
  6. Build the site’s natural mycorrhyzae and microbial population and enhance the health of the soil by raising or maintaining the percentage of organic material content in the existing or imported site soil. Soil must have a minimum of 3% organic material by weight. Test the soil in planting and seeding areas and amend with organic material as needed to meet this requirement.
  7. Where trees are surrounded by hard surfaces (e.g. sidewalks, patios, driveways, car parks, plazas, parking islands) use suspended pavement techniques, structural soils or other comparable methods such as larger tree openings to provide adequate rootable soil volumes. Minimum volume of rootable soil volume per tree shall be:
    • Small trees (e.g. serviceberry): 400 cubic feet (c.f.)
    • Medium trees (e.g. ironwood): 800 c.f.
    • Large trees (e.g. hackberry): 1,200 c.f.

Note: if using structural soils, total soil volumes above need to be multiplied by 5 to obtain equivalent volume of soil useable by the tree.

If above soil volumes cannot be met it is recommended that trees requiring smaller soil volumes be selected. Where applicable, utilize suspended pavement or comparable methods to allow tree roots to gain access under hard surfaces to adjacent open space.

Compliance Tools and Resources

Related B3 Guidelines Documents

Supplemental Resources

  • Philip J. Craul. Urban Soils: Applications and Practices. New York: John Wiley & Sons, 1999.
  • Bassuk, Nina; Grabosky, Jason; Trowbridge, Peter; Urban, James. "Structural Soil: An Innovative Medium Under Pavement that Improves Street Tree Vigor". Urban Horticulture Institute, University of Michigan. Web resource from:

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