Amending Soil at the University of North Texas: Business Leadership Building

Business students will be welcomed at the University of North Texas by a new Business Leadership Building. At 180,000 square feet, this new building accommodates four times the number of students and contains traditional and “smart” classrooms, multimedia learning laboratories, distance learning facilities, a café, study and tutor rooms, and offices for faculty and administrative staff. The building is expected to receive gold-level Leadership in Energy and Environmental Design (LEED) certification, which means it met strict standards for design and construction. 

Managing poor soils in the landscape was a concern for Caye Cook and Associates, designers of the 2+ acres surrounding the new building and adjacent parking structure. Not only were the soils heavy in clay, they were also compacted by machinery in the demolition of the two buildings and a parking lot originally constructed on site. In consultation with the university, the design team established a system to rejuvenate the soils in the turf and landscape planting areas. The general process included:

• Excavation and stockpiling of the best quality topsoil for reuse.
• Weed removal - treatment and grubbing.
• Rip/disrupt/break-up/shatter the soil to minimum 10" depth to loosen compacted soils.
• Removal of all non-soil materials: construction debris and other buried waste, rocks and vegetation.
• Re-compaction to industry standards using standard gill or comparable piece of equipment.
• Placement and tilling of 2" original topsoil along with a few inches of screened black soil to stratify 10" into native disrupted clay soil.
• Placement and tilling of 3" of TXI’s TruGro expanded shale to stratify 10" deep into topsoil/native soil mix.
• Placement and tilling of 3" of well-aged vegetative based organic compost to stratify 10" deep into expanded shale/topsoil/native soil.

In addition to the new soil media, a drip irrigation system, 8 layers newsprint for weed blocker and mulch were added to improve the growing conditions, reduce the need for frequent irrigation and slow evaporation, and restrict the growth of competitive weeds. The roof top on-structure garden area used a blended mix of expanded shale with washed concrete sand and acid compost and had similar drip irrigation and topdressing applications for retention of moisture and reduction of irrigation water.

TXI’s expanded clay is a favorite of landscape architects on projects with clay soils because it’s fired in a kiln at over 2000 degrees Fahrenheit transforming into an inert, inorganic and extremely durable aggregate. And unlike other amendments, it will not float, decompose, or introduce foreign pathogens. When used with a well-aged organic it promotes:

• Better internal drainage
• A moderation of soil temperature extremes
• Savings on irrigation and fertilizer
• More air/pore space for root development
• Less compaction

Not only is expanded shale used in turf and landscape bed development, the lightweight material is also recommended in mixes for container plantings, rooftop gardens, and bioretention area.