Performance of engineered soil and trees in a parking lot bioswale

Abstract

A bioswale integrating an engineered soil and trees was installed in a parking lot to evaluate its ability to reduce storm runoff, pollutant loading, and support tree growth. The adjacent control and treatment sites each received runoff from eight parking spaces and were identical except that there was no bioswale for the control site. A tree was planted at both sites. Storm runoff, pollutant loading, and tree growth were measured. There were 50 storm events with a total precipitation of 563.8 mm during February 2007 and October 2008. The bioswale reduced runoff by 88.8% and total pollutant loading by 95.4%. The engineered soil provided a better aeration and drainage for tree growth than did the control's compacted urban soil. The superior performance of the bioswale demonstrated its potential use for large-scale application in parking lots and roadsides to reduce runoff and support tree growth.

Keywords:

• urban runoff; water quality; engineered soil; bioswale; parking lot

Acknowledgements

We would like to express our appreciation to Skip Mezger and Christina DeMartini Reyes at the Buildings and Grounds Division, University of California Davis for their assistance in site selection, field installation, and site maintenance. We thank Matt Forrest, Dennis Jackson, and Mike Lemaire at Buildings and Grounds Services of University of California for their assistance installing the irrigation system and the parking lot stripping. We appreciate Vince Lampman and his crew members at the Ag and Industrial Services, University of California Davis for their assistance installing the system. We thank Damon Williams and his crew at Operations and Maintenance Electrical for their assistance making the electricity available to the site, and Henry Tsai and Henry Luc for planting and caring for the trees. We also thank Chris Cioni at O&M Utilities, University of California Davis, Cliff Contreras and Roberta Devine at Transportation and Parking Services, University of California Davis for their support on this project. Our thanks also go to Mike Mata at the Department of Land, Air, and Water Resources, University of California Davis for his assistance in the measurement system calibration. This research was supported in part by funds provided by the US Forest Service Pacific Southwest Research Station and by the National Urban and Community Forestry Advisory Council (NUCFAC).