Testing the Stormwater Infiltration of Different Compost Blends in a Bioretention System

Abstract

OLSON, STEPHEN. Testing the Stormwater Infiltration of different Compost blends in a Bioretention system. (Under the direction of Dr. Jennifer Richmond-Bryant, North Carolina State University). Infiltration of rainwater in different compost blends was studied using a contained experiment. Stormwater runoff is problematic on many college campuses, especially those that have grown substantially in size and number of buildings. Traditional stormwater infrastructure often cannot handle the amount of runoff, leading to erosion, flooding, and build-up of contaminants. Several bioretention systems have been studied and utilized successfully on college campuses to help mitigate this issue. Use of compost as the primary medium in a bioretention system was tested in this study based on a need expressed by UNC Charlotte’s Facilities Management Office. Bioretention test cells were built using wood, PVC, and plastic tubs and buckets. Compost amendments were obtained from various sources and were tested over the course of 4 weeks with twice weekly artificial rain events ranging from 0.5 inches to 2 inches. Results indicated a positive relationship between infiltration and moisture content of each compost amendment and a negative relationship between infiltration and organic material content of each compost amendment. It is recommended that UNC Charlotte consider using in-vessel and aerated static compost as a primary substrate for bioretention systems based on the infiltration data and cost. Further studies are recommended to test for compaction of soil over time, different variation of compost, and cross-examination with different plants within the system.