5/11/23 AEG Event: "Bioinfiltration for Stormwater Control”

DINNER MEETING ANNOUNCEMENT

Multiple Lines of Evidence to Decrease Drainage to Surface Area Ratio for Effective Bioinfiltration Stormwater Control

Thursday, May 11, 2023

At the Clarion Hotel in Somerset, New Jersey

Thomas P. O'Connor, P.E., Environmental Engineer, USEPA, Office of Research and Development

ABSTRACT
USEPA constructed bioretention units to evaluate drainage to surface runoff ratio for sizing of bioretention stormwater controls. Three sizes of hydraulically isolated bioretention units were tested in duplicate with changes in aspect ratio of length from inlet wall by doubling successive length from smallest (3.7 m) to largest (14.9 m) while width remained the same (7.1 m). Watershed areas were nominally the same resulting in watershed to surface area ratios of 5.5:1 for largest duplicate units, 11:1 for the middle units and 22:1 for the smallest. Each unit was instrumented for continuous monitoring with water content reflectometers (WCR) and thermistors with data collected since November 2009. The bioretention units were filled with planting media initially comprised of 90% sand and 10% sphagnum peat moss by volume and approximately 99% and 1%, respectively, by weight. These units were then planted between May and November of 2010 with a variety of native grasses, perennials, shrubs and trees that were tolerant to inundation, drought and salt. In late 2012, a survey of shrubs planted in these bioretention units was performed. The published results of the combined analyses of moisture content, rainfall and size of shrubs indicated the smaller units had superior shrub growth due to the more frequent saturation of the root zone as measured by WCR, while the plants in the largest units, particularly away from front wall where runoff entered, potentially relied on direct rainfall only.

Starting in 2017 additional monitoring was performed in these units including chemistry analysis by loss on ignition and total phosphorous of the engineered planting media and an additional survey of plants. As in the previous study, plants did better in the medium (11:1) and small (22:1) bioretention units compared to largest units (5.5:1), and there was greater buildup of organic matter and phosphorous in the smaller units. Oversized units do not completely use the control volume and many of the other original plantings grew slower or were less widespread in comparison to plantings in that smaller units that flooded more frequently and achieved greater growth.
 
BIOGRAPHY
Thomas has been an environmental engineer with the U.S. Environmental Protection Agency (EPA), Office of Research and Development (ORD) for over 26 years. He currently works for the Center for Environmental Solutions and Emergency Response (CESER), Water Infrastructure Division (WID), Integrated Water Resources Branch at EPA’s Edison Environmental Center in Edison, New Jersey. Throughout his career he has conducted research to improve stormwater control design.  Thomas has collaborated with EPA Regions on eight Regional Applied Research Effort (RARE) funded projects.  
 
Thomas graduated with an M.S. in Environmental Engineering from Manhattan College in 1993 and a B.S. in Physics 1986. He has written numerous journal articles (22) and reports (15) and is co-author of three book chapters. He is a licensed professional engineer with New York and New Jersey. He is a member of several professional organizations including the American Academy of Environmental Engineers for which he attained status of Board Certified Environmental Engineer (BCEE). During his EPA career, Thomas has received three Bronze Stars among other EPA awards and accolades. He was named an Outstanding Peer Reviewer for ASCE for years 2014, 2015 and 2016. In 2019, he became and ASCE Fellow.