1. Tyler C. Ladd and Dr. Robert Traver, Villanova University Evaluation of a Porous Concrete BMP: The Hydrologic Perspective Funding and Acknowledgments: Funding for this project was provided by the Pennsylvania Department of Environmental Protection and Villanova University. Special thanks to Dr. Andrea Welker, Clay Emerson, Michael Kwiatkowski, Matthew Prokop, and Matthew Rea for their help and support. Abstract There is an increasing concern about the environmental impacts of urbanization. Impervious coverage such as rooftops and roadways are replacing wooded natural areas. Impervious cover prevents infiltration and creates excess runoff from storms by not allowing rainfall to come in contact with the natural soil. It is this infiltration that replenishes the groundwater which in turn provides baseflow for streams. Impervious systems like gutters and storm sewers channel rain water directly to streams and rivers. While paved areas decrease baseflow, they increase flood flows causing erosion and sedimentation downstream. Innovative stormwater management practices are being developed to help mitigate these problems. Best Management Practices (BMPs) are techniques that can be both aesthetically pleasing and cost effective with the purpose of protecting and improving water resources. Introduction The focus of this study is to evaluate the effectiveness of a Porous Concrete BMP from a water quantity standpoint. In the summer of 2002, the common area between two dormitories, which was formerly an asphalt paved area, was reconstructed and outfitted with three infiltration beds overlain with porous concrete. The site is designed to collect stormwater from the surrounding buildings and grass areas. The runoff is then diverted to three infiltration beds. The site is instrumented to record rainfall, soil moisture levels, and the amount of water leaving the site. A computer model of the site was created using HEC-HMS, a hydrologic model developed by the Army Corps of Engineers. The effectiveness of the BMP is a measure of its ability to infiltrate runoff. The site will be monitored for long-term performance. The results of this study will hopefully encourage the implementation of these BMPs. Pre-Construction Research Objectives -To determine the percent of annual rainfall infiltrated by the BMP -To compare pre-construction functionality with new design functionality -To monitor the effects of antecedent dry days on infiltration -To create a computer model to predict the effects of future storms -To monitor long-term site effectiveness March 20, 2003 Storm – 1.81 inches March 26, 2003 Storm – 0.32 inches March 28, 2003 Storm – 0.59 inches Preliminary Model Results: V-Notch Weir in Stormdrain used for measuring site outflow Instrumentation Water Content Reflectometers used for measuring soil moisture content Moisture Fronts vs. Rainfall Weir Outflow vs. Rainfall Areas Draining to Infiltration Beds Post-Construction Porous Concrete in action Porous Concrete (foreground) during a rain storm Conclusions -The BMP appears to be extremely efficient at infiltrating stormwater -The BMP is exceeding hydrologic design expectations -More storms required for better model calibration -The BMP can effectively handle storms with 2 inches of precipitation