University of Vermont

Two Seniors Wrap Up Their Work on First Year of Aiken Green Roof Research

Greening of Aiken update

Left to right: Seniors Liz Bennett and Sam Wallace collected roof drainage water from tipping buckets to study the first year of the Aiken green roof.
Left to right: Seniors Liz Bennett and Sam Wallace collected roof drainage water from tipping buckets to study the first year of the Aiken green roof.

Elizabeth (Liz) Bennett (ENSC ’14) and Samantha (Sam) Wallace (ENSC ’14) are finishing up their work with Research Associate Gary Hawley on the first year of the Aiken Center’s green roof project. Both students participated multiple times in the Greening of Aiken Intern class and in the fall of 2012, were part of the group that helped install the flats of plants that make up the green roof.

Sam completed an internship with Gary during summer 2013 and worked with temporary employee Kindle Loomis (NR ‘12) on green building initiatives, including surveying the green roof plants to see how they overwintered. Sam also began collecting roof storm water drainage samples. This academic year, she is continuing her work on the green roof and other greening efforts as a paid student employee.

Liz became involved in the green roof project in the spring of 2012. Her work evolved into an honors thesis research project which culminated with a seminar and defense on December 5, 2013 prior to her December graduation. For her thesis advised by thesis committee members Gary, Professor Alan McIntosh, and Research Professor Don Ross (of the College of Agriculture and Life Sciences), she measured flow rate of storm water from Aiken’s green roof and analyzed concentrations of phosphorus, nitrate, ammonium, copper, and zinc in the drainage water.

The Aiken roof is divided into eight watersheds comprising four experimental treatments: Sedum planted in a standard medium of light weight crushed slate; Sedum planted in the same medium mixed with biochar; an alternative mix of plants chosen by an RSENR faculty-led student group and planted in the standard medium; and a control treatment of no plants and no soil that simulates a conventional roof.

Watershed storm and snow melt flows through a unique roof draining system into tipping buckets installed on the third floor of Aiken, where Liz and Sam collected samples for chemical analysis. The tipping bucket system also measures discharge volume and peak flow rates. These data revealed that total discharge was greatest from the control watersheds, as expected, and peak flow rates from control watersheds were almost double that of vegetated watersheds.

Liz conducted chemical analysis of the water samples in UVM’s Agricultural and Environmental Testing Lab in the College of Agriculture and Life Sciences. During her thesis seminar, she reported that although green roofs typically leach more phosphorus than traditional roofs, Aiken’s biochar medium and alternative plant treatments showed potential to reduce phosphorus leachate. She also found roof treatment differences in nitrate, ammonium, and copper that will be studied further.

Both Liz and Sam have benefited greatly from their work on the Aiken green roof. Sam will continue to work with Gary through the spring semester, and Liz will start a new job in January with Roux Associates, Inc., an environmental consulting firm in New Jersey.